Segre Lecture: How Did The Universe Begin?

so good afternoon it's my great pleasure to welcome you today to the annual Amelia gray Distinguished Lecture this is an an autumn and annual tradition for the physics department and we consider it both a pleasure and a responsibility to bring physics the trends the discoveries and the groundbreaking research to the general public and so I want to welcome all of you as well as my colleagues from the physics department the friends of the department and everybody else in the audience we're really delighted that you were able to come today the Amelia C gray lecture ship was made possible by the Raymond and Beverly Sackler foundation the tradition of this lecture was established in 1987 and it demonstrates the sackless commitment to physics education and to research it also honor honors emilio su gray a longtime berkeley professor in the physics department one of the 20th century's most distinguished physicists and of course a Nobel laureate one of our one of our distinguished Nobel laureates in the department which he won for the discovery of the of the antiproton along with Owen Chamberlin so this year's a great lecturer Andrew Lang we also count as one of our own although at this point he's actually at Caltech but we try not to hold that against him too much he is the Marvin Goldberger professor of physics and he's chair of the division of physics astronomy and math at Caltech he did however receive his PhD here working with professor paul richards in 1987 he was very very briefly a postdoc and then became a member of the faculty where he and stayed here until 1994 and it was the work he did then with paul richards that led to his recent the recent awarding of the very prestigious dan david prize for the research they did on the origin the origin of the universe which is going to be the topic of his talk today along with Professor Paul Richards and do I have Paul well do you want to stand up and wave to the audience also you will all so it's a great honor to have both of them here so uh Andrew Lang is an expert in the field of observational cosmology and astrophysics he studies fluctuations in the Cosmic Microwave Background which is I'm sure what you're going to be hearing about today which is a relic of the primeval fireball that filled the universe his group develops novel instrumentation to study the birth and the evolution of the universe he's a member of the National Academy of Sciences of the triple-a s and in addition to winning the den de'vide prize that I already mentioned he has been awarded the ball van prize and was named the California scientist of the year in 2003 an honor which he shared with Saul Perlmutter and his saul here I was going to mention that as well Seoul is back there so Saul there we can so andrew is involved in quite a set of telescopes and observational tools which has a very long series of acronyms which I'm not even going to attempt to reproduce for you but I'm sure he will tell us about some of these remarkable instruments and telescopes that he works with and we're delighted to have him here today to tell us about how the universe began Thank You Francis it's a wonderful honor and great fun to be back here you know I studied I guess I learned my physics courses back at Princeton when I was an undergrad but it's at Berkeley back in the 80s when I really learned how to do physics and now that I'm chair at Caltech I feel at risk of forgetting how to do physics so it's wonderful to be able to spend a few days back here with my old colleagues and and be learning again I'm going to I'm going to talk to him a very interesting question how did the universe begin and I often start my talks with this wonderful woodcut which comes from a French astronomy textbook published in 1785 I don't know exactly what the artist had in mind but whatever it was he was incredibly prescient of what we would be doing hundreds of years later because we've now developed the techniques and the technology to literally look out beyond the most distant stars and the wonderful thing about cosmology about using a telescope is a telescope is really a time machine we're looking so far out that we're able to look back in time and as you'll see now to make images from very shortly after the universe began and much like our Explorer here in this picture the universe that we see way back then looks very very much different from the current universe and by comparing what it looks like back then to what it is today we learn very much about what the universe is made of and how its evolving so I could ask if we can turn down this spotlight a little bit and also turn down the room lights a little bit Maria there's a there's a light switch right here or no he's got it that's great okay so yeah I have to stay here if I look out at the sky and I look at the wavelengths that our eyes are adapted to the deepest image ever taken to the sky is this it's called the so-called Hubble field this entire bit of the sky picture putting a 1 millimeter pinhole in a bit of cardboard and holding it at arm's length and looking at the sky through that little pinhole that's how much sky that we're looking at here right and you see that there are actually thousands of objects in this little data sky and it might surprise you who those of you who are not astronomers to know that very very few of these our stars only a half a dozen or so everything else in this image is a galaxy and that's quite remarkable here I've blown up a little inset here and you can see a very beautiful grand spiral galaxy much like our own Milky Way looming in the foreground it's one of the larger galaxies in the image it's fairly close to us and then you'll also notice as you go further out that the galaxies tend to look smaller and bluer and that in between them it is dark now I have to admit something I'm described as an astrophysicist I really know almost nothing about astronomy but I'm going to justify that in a moment so what I can tell you about this picture and this is a little tongue-in-cheek is it is not the case that little galaxies are blue and big galaxies are yellow the reason that all that the smaller galaxies in the picture are blue is that they're further away and in fact they're so far away that we're looking at them in their youth and their adolescent youth when the very hot bright UV stars are burning and much like a graduate student is more energetic that a professor these galaxies despite their redshift actually appear bluer here right and they're going to grow up someday to be galaxies much like this that's a very interesting story we've already learned that the universe is evolving that it's easy even relatively even using the Hubble Space Telescope to look back to the time when the universe looks different and it does today but from the point of view of the Explorer on the previous viewgraph this image is a deep disappointment because try as we like if we look in between the galaxies all we see is dark so it turns out there is though a for us to see much much further back in the history of the universe to do that we have to look in a very different way and to describe that I have to teach you a few things about cosmology one of the reasons that I went into cosmology when I did I'd always been fascinated with the origins the universe but I found fortunately that very little was known about cosmology back in 1980 in fact this slide summarizes everything that we knew back then so I can teach you all of basic cosmology in about a minute at least as we knew it back then so the universe is expanding and this is my one very Cal tech centric slide I have to apologize for it discovered by Edwin Hubble up on Mount Wilson close to the Caltech campus if you play that movie backwards you could imagine that matter was all in a much smaller place and perhaps it was much hotter things tend to cool as they expand and Willie Fowler and his colleagues in the Kellogg laboratory down at the Caltech campus worked out the theory of what would happen in that very hot dense early universe how the light nuclei would be would be synthesized much as they are in the center of our Sun and that was quite an interesting piece of work and what he was able to find was that you could the relative abundance of the light elements hydrogen helium etc was going to be determined just by one parameter which was the density of matter in our universe and as we'll see later the theorists at the time had reasons to believe that this density was exactly the critical density the density we thought at the time would be necessary to just halt the expansion of the universe Fowler and his colleagues work out a theory that was then used by observers who went out and looked at the relative abundance of light elements they found that the density was only about five percent of that critical density right the theorists being theorists said close enough right yeah you know obviously you've made some mistake in your measurements it's close enough to one its cosmology after all okay so people were pretty happy then in the last fact that you need to know is that and this was discovered in 1964 in New Jersey of all places using a very odd telescope by two people who've gone on to win a Nobel Prize and that if you look up at the sky at night and if or during the daytime for that matter if your eyes were sensitive to microwave radiation you'd find that the whole sky was growing glowing rather and glowing fairly brightly certainly brighter than the emission from our own galaxy for example right so that's a stunning fact and that is literally the glow left over from this primeval fireball that filled the universe when it was in a hot dense state okay so this is a physicists history of the universe and I don't mean to be demeaning to the astronomers okay but let me run through this story and then you'll see why I've put all of the astronomy that we usually think about in parenthetic terms here so in this picture this is the present day this is me looking through my telescope and as I look out I look further and further back in time so there's a timeline here right and then we have things that are present at various epochs of the universe right so we start at at a very very early time and that's something that I'm going to get back to a little bit later in my talk we don't know exactly what happened back then but we have some very very good Clues right now what we do know is that about a second into the lifetime of the universe it was in a very hot dense state so hot and so hot that matter and antimatter were produced in copious amounts and as the universe expanded cooled and the temperatures dropped one could no longer produce matter and antimatter so copiously the matter and antimatter annihilated and when you take proton and antiproton for example and annihilate them you get out light photons gamma rays okay and a very good approximation a few seconds after the Big Bang whatever that was the universe was filled with light and that's about it fortunately for us for reasons we don't entirely understand there was approximately a one part per billion asymmetry of matter over antimatter and that's tiny residual the one proton that was left over after the other billion annihilated with the billion anti protons that's what we and earth and the entire observable universe are now made of so we don't understand it but we should be thankful for it right we'll come back to that for now what's important to understand is during the first minutes hours and in fact the first few hundred thousand years of the universe what you had then was mostly light photons the photons started out as gamma rays they cooled they red shifted to the UV to the visible during all this time you had a very dilute mixture of matter that was caught up with the photons because the matter it was still so hot that the matter was ionized it was strongly coupled to the photons if you'd been alive at this epoch of the universe and you had looked around you it would live looked very foggy and dense you can't see through an ionized plasma and try looking through a candle flame for example all that changed very suddenly on a cosmic timescale at around 400,000 years or so after the Big Bang and at this moment the universe cooled to about 3,000 degrees or so and that was cold cool enough now for atoms to form for the first time so you had the electrons now binding with nuclei and what happened is the universe became neutral so it was full of neutral gas primarily hydrogen and and helium and that released the light and now these photons streamed off and to very good approximation never interacted with anything again for the history of the universe for the next as we'll see thirteen and a half billion years until some of them end their lives in my telescope so when I look out from this early time and if I look at the right wavelengths today which are wavelengths of a few millimeters or frequencies of a few hundred Hertz in the hi microwave region but I look out at the sky I see a crystal-clear snapshot of this surface which I'll call a photosphere and it's a snapshot of the universe at this age right now why have I ignored all of astronomy and all those beautiful images of all those galaxies well it's a fact that even though the energy density of this radiation continues to decrease as the universe expands to this day if you just take a census of all the electromagnetic energy in the universe and you ask what what comprises the bulk of it well it turns out that the vast majority of it more than 90% is still in the form of this microwave background radiation the energy density and this stuff is still much greater than all the light that's ever been emitted from all the stars that have ever shown so being a physicist if you know physicists proceed by judicious oversimplification of problems and I'm going to ignore all the light never ever emitted by all the stars and I'm just going to study this stuff and it's particularly nice because it's going to give me a picture of the very early universe so what do we see well at first it's rather a disappointment right if you look out at a sky at the sky this is actually a very accurate map of what the entire sky looks like at least what it looked like for the first few decades in which many many attempts were made to see the structure in this radiation and it turns out to be extremely uniform and in fact even though it was discovered in 64 it wasn't until 1992 that george smoot experiment on the COBE satellite this so called EMR or diffuse microwave radiometer revealed this image right and so what I've tried to do here is simulate turning up the contrast right on that previous image and at first and I think George picked these colors I can't be blamed for them but at first what was seen were some very very large structure on the sky that the the intensity variation or the temperature variation in these structures is only about ten parts per million of the absolute brightness or temperature of the radiation but it was very important to see them at all at the time because these are the first though unresolved hints of structure that would later in the growth of the universe go on to become the very largest structures that we see today so this represents slightly hotter and and cooler spots on the sky now I have to pause here for a moment now I've set the stage and I'm going to tell you a story and the story is a very human story and it's about friendly competition and races etc etc but I want to celebrate the fact this is somewhat unusual you know one of the most wonderful things about doing science yes the discoveries are wonderful but truly the most wonderful thing about doing science are the human relationships in science and there's no relationship more wonderful than the relationship between a PhD mentor and a PhD student which usually lasts a lifetime especially if the student goes on to become a professor somewhere else it turns out that in this fields and these characters are going to appear again and again in the story tonight we have five generations five academic generations up and they represent all the various stages of the academic career Paul who you've already met this evening is the professor emeritus I am now as Francis described the administrator so I was Paul student this fellow as unlikely as it seems is a professor at at Berkeley built the whole sackful is here we'll meet him at the end of the talk and he was one of my first students all right and then Bill's first student child and Crowe graduated from Berkeley in 2003 is now did a postdoc with me is now an assistant professor at Stanford and chow-chow Lynn is here tonight child Lynn quos one of his first students perhaps his first Jamie Tolan is it is true doing his degree at Stanford but was a Berkeley undergraduate right so you can see that Berkeley really is the center of the universe here now now Adrien leaf it's in the story - he's a slightly different lineage he did a postdoc with Paul so I think he's Bill's cousin or something right in this in this family hierarchy right but so you've met the whole point right and it's I have to say personally really wonderful that all of these people can be here tonight all right now back to our story remember what we learned first about the microwave background was that it's very isotropic this itself was big news for cosmology if the radiation that's just getting to me from this direction and from this direction right it's been traveling the entire history of the universe it's just reaching me now somehow it knows how to be at exactly the same temperature to ten parts per million how is that right unless you just dial that in unless you just say that's just the way it was right you need a better explanation than that and the explanation the first explanation has come up with by Alan Guth and then in a theory that went through through several several different stages Paul Steinhardt leonard leonard susskind and others contributed to the idea the idea was a fantastic idea and it was that you know the universe was not only once upon a time just small it was really really small and what they hypothesized was that the entire observable universe today was one smaller than the nucleus of an atom and that for whatever reason at a very very early time ten to the minus 35 pick whatever large number you want to put in here seconds it inflated that is it expanded at superluminal velocity all right the two edges of it expanded away from each other faster than the speed of light and it inflates um sub-nuclear dimensions to macroscopic size showing as a few meters here this is a wonderful plot you can't go wrong there are a hundred decades along this axis and sixty decades across here okay and then this process stopped and then the expansion that people had always imagined was the BIGBANG expansion took over okay now this basically solved this problem this is a bit of a hand waving explanation but it solved this problem because the universe having all been in a very very small place even I'll be it for a very short time had had a chance to thermalize and reach the same temperature now it had been expanded very rapidly outside what we call the event horizon and so the things the the signals were just seeing now today from these two very different directions that are reaching us now in this model it makes sense that they're at the same temperature I thought that this was a fantastic theory it appeared the first year I was in graduate school here with Paul and I and I use that the the adjective fantastic in the most negative sense of that word because because it hit all the action here way back you know at a time when who will ever be able to test that right however it did predict that the universe is flat and many of us noted this and many of the folks in Paul's group at the time set out trying to figure out how we were going to test this thing because you know this became the standard Dogma in cosmology obviously in in need of tests now what is what is flat mean it really means that the universe today has a special critical density of matter and energy and specifically it doesn't mean that the universe is flat like a like a pancake what it means is that if you built a very large triangle in our universe and you measured the sum of the internal angles you get exactly the answer that your high school teacher told you you should get 180 degrees that seems self-evident however you'll notice that if I put a triangle on a two-dimensional surface that's curved like on the surface of a sphere if i sum these angles there'll be more than 180 degrees if I put it on a hyperbolic surface a kind of saddle shape and I sum those angles they'll be less than 180 degrees and so this is just telling you that by building a large triangle large compared to the radius of curvature of the space and measuring the sum of the internal angles you do in fact test what the surface is that your that that you're living on so you can imagine ants living on the surface building a triangle and even though they're not aware of the curvature walking around and doing these these these types of measurement okay now you can do this experiment at home you can build yourself a triangle and you'll be doing cosmology it won't be very sensitive right because the triangle is small right we want to make a very very large triangle the largest triangle we can make would be represented by a graduate student say holding up a meter stick out here at the furthest distance that we can possibly see right because that makes a triangle if I know this distance right and I know these distances and I can figure out what the angles are then I have done this test and it's a brilliant test because that triangle now includes all the matter and energy along the line of sight and what Einstein taught us is that depending on the amount of matter and energy along this line of sight the straight line in our universe which is defined by the path that light travels right that the matter and energy along his line of sight will either magnify or D magnify the image of this very very distant object and so it'll it will affect the curvature of these rays so this is a wonderful program and it suggests using microwave background measurements the only thing that's missing is what constitutes the meter stick out here I have to know what this what this distance is so now we go back to what I've already taught you remember in the early universe before the first atoms formed there was mostly light and a little bit of matter now the little bit of matter it turns out had more dense and less dense regions and that's what's formed all the structure that we see in the universe today the more dense regions tried to collapse gravitationally however they were strongly bound to the light while the atoms were still ionized and so they would collapse they would drag the light with it it would heat up the temperature would rise and it would actually bounce you can think of this as a sound wave if you like the people in the field call these acoustic waves in fact that are traveling through the early universe so in this simple cartoon picture there is a largest scale that will have had time to maximally collapse and compress and heat up by the time the first atoms form and that's what sets our length scale in this very very simple picture then as well there should be a harmonic series of smaller and smaller length scales corresponding to smaller and smaller scales that have had time to compress and re expand compress we expand and cool in fact and so on and so on and so what makes this possible is that the physics of the very early universe is actually very simple much much simpler than any of these topics that occur later in the history of the universe so back in the day and now we've reached a time I guess we're at about let's say 15 years ago people were were making simulations and simulating what the microwave sky would have looked like if Kobe had had enough resolution to resolve this angular scale it turns out that if inflation is correct this angular scale turns out to be about one degree on the sky that's a very happy fact could have been a micro arc second this would have been a much more difficult field right that's about a degree on the sky the resolution angular resolution of the Kobe experiment was about seven degrees right so we need to build an experiment that has significantly better resolution than Kobe if we did this is kind of what we'd see right and this is literally this would is a snapshot of what the early universe looks like these are sound waves that are bouncing around through the early universe and the poetic idea of inflation is that the origin of these slightly warmer and cooler spots that would we'll go on to form all the structures that we see in the universe today the origin is actually quantum mechanical fluctuations in the density on a subatomic scale that by the process of inflation have been stretched large to cosmic distance scales that is really a fantastic idea now maybe I'm using fantastic in the positive sense if it's true all right so so how can we test this and more specifically now I need to teach you just one kind of technical thing so you can understand the beauty in the rest of the science here we need a way to quantify what this picture is right so what we're going to do to the picture is very much what what your stereo equalizer does at home to the music that's going through it we're going to sort it into the base notes in the treble notes right so for example if I take the flute right playing this note 392 Hertz and I do this process to it before ei transform I take a spectrum of it I get this spectrum out and we get the fundamental here and then you'll see there's as many any of you who play music probably know there are a series of harmonic overtones right and the relative amplitude of these harmonic overtones differs depending on the instrument for example here's a flute and here's a violin right and if I flip back and forth you'll see that the relative although they're playing the same note they're rips sorry about that the rest of the spectrum looks different and that's what to your ear allows your ear to tell the difference between the same note played by a flute and a violin so in an exactly analogous way these sound waves that are racing through the early universe depending on the geometry of the universe are playing a note if you will and if I take that map and I analyze it and focus just for a moment on the curve that's surrounded by the red here right so if I took that previous map and I analyzed it in an analogous way I would get a fundamental tone a note here and if inflation is correct now this would correspond to an angular scale so this is now since it's a spatial spectrum this is not frequency its spatial scale but the are the large angular scales corresponding to the bass notes that Kobe was sensitive to and these are that the small angular scales corresponding to treble notes and basically what we're trying to do is to build in the stereo analogy a high fidelity version of Kobe so that we can detect the high notes and particularly resolve this peak and the position of this peak is going to determine the geometry of the universe it's going to basically it is it is a measure of the total amount of matter and energy in the universe right and if there is less matter and energy it shifts this way and if there's more it shifts this way and then in a good analogy with with music the relative height of these various peaks is going to tell us about the content of the universe all right so here's the trick you're a graduate student Kobe took many years and many hundreds of millions of dollars to make this measurement you want to make a much better measurement and you want to do it in a much shorter time for much less money so what do you do well what Paul taught me to do is build a better detector and this is a detector the idea for which came up while we were still up here at Berkeley and we actually managed to to make it a reality after I'd move down to Caltech so it was developed at it down at JPL and I won't go into the details it's incredibly simple and like most simple things it works really well this is a little chip of silicon there's a little spiderweb structure here and all you need to know about it is it's it's made of very very thin beams they're only about a micron square each most of the material has been etched away here wherever you see black it's just free space and then lurking in the middle of the spiderweb is a thermometer and the way this device works is we focus the heat from the big bang on it we measure how much it heats up and that's it what could be simpler to make it very sensitive you make it very cold and so it's operated at a temperature of a few tenths of a degree above absolute zero it turns out to work so well that what took four years for Kobe du becomes about three hours and that speeds things up a lot even enough for an impatient graduate student and you can then for example you don't need a sidelight you only need a few days preferably above the Earth's atmosphere to make this kind of measurement and if you're impatient about getting on a satellite this is a poor man's satellite it's a very large balloon down in Pasadena I describe it as the size of the Rose Bowl and that's exactly how big it is it's it's a very delicate apparatus but people have been flying these for years and you can hang a payload of several tons on it and now our story really begins in earnest right so we had these detectors and we wanted to race out and make this measurement because this was very very exciting so two teams formed and they they used to very similar but slightly different approaches and there was involved in this a lot of very friendly competition and I think it made us both go faster and do better work so here's a the berkeley team there's paul adrian lee and some others and their experiment is called maxima this is their balloon borne telescope and boomerang was a team led by me and a colleague Paola Durbin artists in in Italy and I've showed you a picture of boomerang here with all of its shielding stripped off so you can see what these things look like inside this looks not not so different from this it's very very simple you just take an off axis parabolic mirror you focus the heat from the big bang up into this big thermos bottle and you have a few of those bola metric detectors inside you point it one way or another on the sky and you measure the temperature of those detectors and it's remarkable that something you can build with your own hands more or less can actually tell you what these tiny temperature variations are coming from the early universe now the real difference between these payloads is that this was designed to fly over Antarctica and this was designed to fly over the u.s. this is a safer and more reliable way to do the measurement but you don't get as much time right and this is a little riskier so we spread our bets as a larger team and we we attempted both it turns out that both worked extremely well so boomerang we took to hear the McMurdo base on the edge of the Antarctic continent and this was still kind of in the in the pioneering days of doing us turns out if you launch at just the right time of year which turns out to be Christmas Day plus or minus a few weeks there's a something called the south polar vortex that sets up and the winds will blow you around in a big circle at almost constant latitude around the South Pole which is here and this just to give you a feel for what it's like to work down there the payload is launched from the airfield which is out at the end of this thing which is euphemistically called a road alright and there's a lot of a lot of stories about getting back and forth to the airfield right and this is what the payload looks like when it's all put together and dressed up it's much like a small satellite the sun's always up we're going to try to fly for 10 or so days so we can't run off a battery so we run off of solar panels we drive out to the launch site this is what a balloon launch looks like this is just a little tip of the balloon which is inflated with helium this is all balloon there's a parachute which will come in handy later what the pay what the telescope looks like and beautiful active volcano Mount Erebus in the background and this is a really heart-stopping moment that that all of us live through when you hope that you've actually turned everything on because it's not coming back it's that panic like you've left the house to have the cell phone the wall let's say so we were very very lucky on our first flight this is this is our path we flew 5,000 miles in about 10 and a half days we came back so close to where we took off that we could see the payload coming in over the horizon for a day beforehand we just waited till it got due south of us very importantly it didn't come back you know it came back in this direction and not this direction from where we took off this is open water out here and it landed down on the ice shelf and this is what a perfect landing is called looks like so what did we do well long story short after a year of analyzing data what boomerang did during those 10 days is it scanned a relatively small bit of the sky just a few percent of the sky I've tried to make it more or less to scale here right and here's the Kobe map and here's the boomerang map and we've put these now in colors which I like because they represent what your eye would see if you'd been around at the time back when the first atoms were forming it's a temperature of about 3,000 Kelvin this kind of dull orange color now this is the size of the full moon if you can see it down here and the red the angular resolution of this of the experiment was about 7 or 10 arc minutes or so it's not so different from the size of my laser pointer and so you can see now that there's a characteristic angular scale of structure here which is much larger than the size of the laser pointer what this means is if you make this map with a higher and higher angular resolution it's not going to look a lot different than it looks here and so for the first time we were resolving what the early universe actually looked like and I call it the embryonic universe because in terms of the life of the universe this is an image of what the universe looks like at 400,000 years it's equivalent to two imaging most of you in a few hours after you were conceived depending on your age and and that's a nice analogy because the you were still a single cell then that embryonic form doesn't look anything like the adult form but a biologist could look at the DNA the DNA in that cell and tell what its going to grow up to be and in a similar fashion by studying the the very very fine details details that are very difficult to see with your eye in these maps and comparing it with the current adult universe we learn a lot not just about the geometry but also about what the universe is made of right now oh and I'll just I just threw this in because just to show you it's not difficult to see these structures because they're small on the sky this is actually our data displayed in a different way projected on the horizon as though if you somehow had eye sensitive to both visible and microwave this is what the sky would look like it would be frightening but it's not that they were too small to see that took so long to see them it's that they're very very faint structures now at the same time Paul and Adrienne and showels team were were flying Maxima over over North America now I include this because I have also been subjected to this the graduate students always say very important projects for the professors when they come down to the field because it's well known that if you don't have a special project for the professor he'll cause a lot of trouble he cuts into the field so I was amused that Paul sent me this picture this is what a balloon launch looks like in in hot humid Texas it's a little different and this is what a landing looks like you can take your pick I don't know if it's more difficult to go to Antarctica or to Texas but what came out of this was an equally beautiful map and it is a credit I want I just want to pause for a moment this had been a goal of many many research teams for many many years and collectively the two groups wound up getting to these results within months of each other right so you have this very very beautiful map it's a smaller map but it's a map of a smaller area of the sky but with slightly higher resolution and it's really really quite beautiful the way you can see the structures here I've tried to put two maps that the two maps together more or less to the same scale they're of radically different parts of the sky one is visible from nor America one is visible from from over the Antarctic but you can see that's that statistically they look like the same map so what do we do with those maps I'm clicking there we go so this is just to set the stage this is our ones attempts to figure out what the power spectrum look like remember those beautiful plots were if we could measure the spectrum we'd find out about the geometry and content of the universe in 1999 just before these measurements many many experiments had been done some of these were done by our groups many by other groups and you can see that despite all the trying not a clear picture had emerged and this is the first results that came out of maxima and boomerang so here's the Coby point down there that kind of set the scale and here you see this first peak emerging very very beautifully with excellent agreement between the new the the two experiments so this was really a big moment in cosmology this happened in the year 2000 it's nine years ago now but for the first time we felt we really understood what the geometry was and it was a bit of a disappointment in a way for me because remember I'd set out more or less to disprove the theory of inflation and here with the result we got was perfectly consistent with inflation so this is the best fit line this solid curve is exactly the prediction that inflation makes all right well so there are other tests of inflation and what you want to do is notice that in the data here it's not these these higher harmonics are certainly not clear in the data but we had only analyzed a small bit of the data and now another one of the cast of characters enters so bill Holtz awful at this point took on building a larger telescope and the great thing about a larger telescope is that you're able to do the observations from the ground the effects of the atmosphere aren't so bad if you're trying to work on smaller angular scales and that's what the larger telescope is is is designed for it to get to smaller angular scales now bill took this experiment back down to Antarctica but now for a completely different reason not to put it on a balloon it's going to the South Pole proper this is what the South Pole looks like as you're flying in from a plane it's a relatively isolated lonely place this is the runway this is where one lives during the winter this is an area affectionately known as summer camp where where you can live while the Sun's up at least most of the time and then all of the telescopes and there are many of them are located over here it turns out to be actually a wonderful and fairly convenient place to do astronomy unlike most observatories you don't have to drive up a terrible road to get to the top of a mountain you just have to stroll across the runway to get out to your to your to your telescopes there all right all right so this is the Ackbar experiment being lifted in and you can judge for yourself whether this is really easier than ballooning this is I'm not sure who this is bill what bill would know he'll he'll he'll tell us later but it does get very very cold that the telescope is designed to to run all during the Austral winter it's not infrequent that it's minus 100 degrees Fahrenheit outside during the winter and the intrepid winter over has to go out every few days to transform transfer more liquid helium into the machine so by 2002 and notice now this is only two years later than the earlier slide so progress is happening very rapidly now we've now constrained the spectrum with much higher precision right so what you see here now and these are all measurements made with this device another balloon had flown called archeops had measured more of the sky out at very large angular scales more boomerang data had been analysed and now not only do we see the first peak but we see very beautifully the second and the third peaks and Akbar had come online and was beginning to produce data and child and quo was Bill's first student was analyzing this data and beginning to produce the spectra which were consistent right not very accurate yet at the large angular scales but which were beginning to nail down and if you have an imagination maybe even detect more Peaks out here but you'll see in a moment that it got much better so where are we today many many experiments have been done now because this is an important topic and I'll just show the data from from three of them truth be told boomerangs not really relevant anymore it's been superseded W map which is the NASA satellite all the way out here at the second Lagrange point a million miles from the earth and Ackbar down at the South Pole pretty much tell the whole story and this is what it looks like and it's quite remarkable now we see one peak and two and three and four I'll talk to you later about whether we see a fifth alright and on and on and so this really makes a believer out of me right and this spectrum this red curve is a model fit is precisely consistent with inflation in several different ways I've only had a chance to describe to you the one test of geometry but there are other tests which have to do with the width of this peak for example which it passes with flying colors so this is really really beautiful you know these are not large signals these are only tens of microkelvin tens of tens of millions of a degree temperature difference one part of the sky to another many different experiments all beautifully done getting yielding the same results okay so what have we learn from this when we compare these maps with the universe today as I've said they're consistent with inflation we get an age out which turns out to be much more precise than the ten or twenty billion years that we've entered about for most of my lifetime it's we now can say it's 13.7 billion years old but the really extraordinary thing and it's somewhat disturbing is that we learned well no this isn't disturbing this is gratifying so the theorists were wrong about Willy Fowler being wrong Willy Fowler and the observers were right the amount of ordinary matter in the universe Adams's etc is in fact only about four and a half percent and yet the theorists were right that the total density is exactly this density that's necessary to just make the geometry of the universe flat but ninety five and some odd percent of it is made of other stuff and that the other stuff comes in two different flavors twenty three percent of the total is some form of cold dark matter some other relic of the Big Bang probably in the form of a particle that we just haven't discovered yet and then the really disturbing thing is because this is you know something we can grasp over two-thirds of the matter and energy in the universe is in the form of something called dark energy which is a technical term which we use to encapsulate our ignorance of it dark energy has the remarkable property discovered as I'll say in a moment before these measurements were made that it is causing the expansion of the universe to accelerate every day right so we knew about dark energy before the CMB results and we knew about that thanks to the work of Saul Perlmutter right this is my favorite my all-time favorite cover of science magazine I think with the artist who did this it did a great great job and I don't have this is a whole nother great lecture that's all we'll have to give someday but by looking at the brightness and redshift a very distant supernova and mostly by developing clever techniques for finding lots of distant supernovae Saul and his colleagues set out to measure the deceleration of the expansion it is an old question in cosmology the universe is expanding but we know that there's gravity acting between the galaxies so it must every day be gradually decelerating and how if we could measure how quickly it was decelerating we'd measure all the mass in the universe it's a brilliant technique and the most wonderful thing happened Saul and his group went out and found out that it wasn't decelerating at all it was accelerating and the we don't we still really understand that at least I don't but the way that we describe that is that there is this dark energy we call it Omega lambda lambda after the famous term that Einstein took it stuck in his equations by a mistake but somehow cleverly he was right in the end that so for most of our lives in cosmology the big argument was the following this is a plot of the amount of this funny dark energy here which we always thought was zero so for most of our lives we were arguing about where on this line we are and this is about the amount of matter of all sorts right and you remember that Willy Fowler and his colleagues and observers argued that this number the universe was a point right around here about 5% of this stuff and none of this right and then people who studied the interaction of galaxies and how they orbited about one another in the universe said no no there's more matter than that they argued that we're at about 30% right around here and the theorists argued with religious fervor that we had to be here because they knew that the universe had to have this flat geometry right now flat it turns out once you admit the possibility of this stuff well you have to add this and that that determines the geometry so flat turns out to be anywhere along this line what Saul and his colleagues did back in 1997-98 was to realize by studying the distant supernovae that in fact we were somewhere along this trajectory here and then the microwave background measurements came in and here's the result from boomerang and they constrained us to be very very close to flat and so when these two results were combined and I needn't point out but I will anyway that both of these results had an enormous heritage from Berkeley okay this is the place where all this happened that they constrained us to this place where it's about two-thirds dark energy and one-third matter so it turns out that everyone was right Willie Fowler was right it's only 5% of ordinary matter the astronomers were right it is about 30% matter they just didn't you know it's 25% of is some other kind of matter and the theorists were right - it is it is flat so that's kind of a happy okay and it turns out now well this is just another justjust in in more detail if you combine the microwave background in the supernovae with also we get more clues from the distribution of galaxies around us in the universe today that we can confine it now this is an old view graph so it's actually constrained much better to that but you can see that the the data indicates something very very close to flat and about maybe 75% 25% or so okay I'm going to show you another picture now because I have to tell take a brief pause before I continue with the rest of my story which doesn't go on too much longer but uh you've noticed that Berkeley produces a lot of the important cosmological results in the world why is that and it does so either directly or indirectly through the students it produces we've mentioned Saul who was a young protege of rich Muller who was thinking about how to do this measurement way back when you know of course by the time the measurement was done rich was on to the thirty fourth new idea that he'd had since then right rich also had a big influence on George Smoot who is responsible for this important measurement and Paul has produced many very important students most notably John Mather who won a Nobel Prize along with George for doing this measurement which is I think reasonably described as doing your thesis project over again really really well okay and so these two guys I just want to pause for a moment you know because I was thinking you know what is it that makes Berkeley such a great place in terms of training physicists or just doing physics right is it the easy availability of parking no okay so what is it and I think what it is is that you have really what I call inspiring visionaries physics cysts who are so inspirational that they set those of us like myself and some others here on lifelong quests to go out and do things and it takes decades and we struggle and we eventually do it really really well and by that time these guys you know Paul was originally trained as a condensed matter physicist now they're on to the next thing already but these these kinds of faculty are really what makes a department really really great so I want to thank Paul for that mentorship all right so let me now get to the end of my talk what comes next so we've talked about how we can see back to the embryonic universe and we've talked about how our attempts to do that have given us maps what the universe looks like then and that those maps are all consistent with what inflation would predict okay but we'd like to look back much much further still because in a way we've barely touched the surface although it's far back in terms of linear time in terms of logarithmic time we it's really nothing right in this graphic which comes out of some magazine we're here now present day right and what's fascinating to a physicist is if you could somehow look yet further back in the history of the universe you could reach energy scales that we will never reach with any particle accelerator that we'll ever be able to build on the face of the earth so there's really interesting physics going on here this has been noticed by a lot of physicists the problem is I've already described to you we can never see past this this wall this is the opaque wall and it comes to electromagnetic radiation yeah get out that far the atoms are ionized and that's it you can't see further so we have to use something different if we're going to see further and theorists have suggested that we can use gravitational waves because the universe turns out to be transparent all the way back to gravitational radiation what is gravitational radiation to make light an electromagnetic wave you take a charged particle you shake it right and it the ripples in the field line constitute that electromagnetic wave if you take a mass and you shake it alright the ripples in the gravitational field line constitute a gravitational wave it's that simple right turns out gravitational waves are much much more difficult to detect than electromagnetic radiation right and in fact this would be almost hopeless I'll interject it'll just take a minute big project at a Cal Tech is LIGO LIGO has spent hundreds of millions of dollars and some decades I go into my office every morning waiting for the little post-it on my desk we've seen one because it's in my division and we have to manage it I meet with the director every week so far no post-it note the mirrors they have two mirrors hanging in a beebe tube four kilometers from each other they are monitoring real-time as we speak the distance between those mirrors to a precision equivalent to measuring the distance to the nearest star to one micron okay no signal okay now this gravitational radiation inflation would have been the mother of all accelerations and would have produced generically a gravitational wave background akin to the Cosmic Microwave Background the universe would be filled with gravitational radiation but LIGO is never going to see it it's red shifted too you know we're looking at wavelengths which are the scale of the universe so how can we see this it turns out to imprint itself in the polarization of the microwave background if it's there I was so delighted to hear this because I'd invested a lifetime into developing this kind of technology so the see I have to tell you the microwave background is polarized it's polarized at this at a very small level it's about 1% of the temperature what does that mean for those of you who don't know a lot about electromagnetic waves all you need to know is that there's an attribute of the radiation called polarization it's the reason your Polaroid sunglasses work and it simply means that the electric field is a little stronger in one direction than in the other and a lot of light has a small partial polarization so we understand this process very very well and in fact as I'll show you we've now measured it in the microwave background it's challenging because it's yet a hundred times fainter than the images that we've been able to make after such a long struggle and now it turns out and the theorists they like to tease us you know having having gotten the images then they they set something else out in front of us and they they wiggle it and they say oh you know you'll be rich and famous if you discover this one but the trick is the amplitude is 10 nano Kelvin okay and so this is the polarization of the CMB I'm going to flip to now what it would look like if there was gravitational radiation at a pretty substantial level and that's it so if I flip back and forth you'll see you'll notice a difference the difference your eye is drawn to is the colour change but we can't use that that's cheating the temperature changes are degenerate with other things so you have to look for the little twitches in these lines here can you see those that's what we're going to have to look for all right so we have to simply do and the reason that we can see these at all is that this polarization has a very very special symmetry and I'm not going to try to explain it to the to those who haven't had freshmen enm at UC Berkeley but to those who have this is a pure --mode it has no curl and the gravitational radiation whoops sorry distorts that and produces a little bit of curl so we have to measure 10 nano Kelvin signal with enough fidelity to do vector calculus on it and separate the curl and long curl modes right if you're not impressed you should be so next generation of experiments and interestingly things have sorted out again we're in another race and again it's a very friendly competition down at Caltech we built something called bicep notice what a little telescope it is the only saving grace in these pictures is that the signal this angular scale here is big on the sky even bigger than the temperature and I saw trippy so I'm looking for a signal which is several degrees big on the sky what that means is if I choose to I can use a smaller telescope so this telescope has just a 25 centimeter aperture that makes it a little easier and cheaper and faster to build so this was the first out of the blocks and it was actually spent three years observing down at South Pole already 2006 through 2008 Bill Holtz Apfel was involved in this as well as Shaolin Kuo who was a postdoc in my group at the time so we have these three of the cast of characters and just another shot of South Pole Station to tell you what a gorgeous place it is to go as a tourist you're not allowed into the greenhouse library saunas or basketball court but if you can get yourself hooked up to one of these experimental groups you can use all of them and it's a great deal of fun this is where the Akbar experiment was sited and this is a bicep and its sister experiment quad and this is bicep getting lifted in to its home we have only a few months to go from things and crates to a fully working telescope but there's the team there's Bill Holtz Apple here with a almost fully working telescope the Sun Goes Down for those of you who've never caught the green flash it's easy to catch at the South Pole it just sits there for a minute so you can go out and take a picture of it and then there follows a very very long night nine months long minus 100 fahrenheit and our winter over who operated the experiment in its first year was driven by distraction to do remarkable things in minus 100 degrees sorry right so this is now the state of the art in this field this is now an analysis of the first two years of this data and this was just published the just a few months ago so we're kind of up to the present thing now measuring the temperature has become child's play this experiment does this every few hours right we just make make make maps like this this is easy what's more difficult now and here's a map and I've done this to help you visualize it it's a map of the normal prosaic form of polarization the polarization we would expect to be there in the absence of gravitational radiation and notice that the scale the contrast has been blown up by a factor of a hundred so we're going now two orders of magnitude deeper than the images that we made with maxima and with and with boomerang and you can see that we're seeing structures with pretty high signal-to-noise there and most importantly we're able to discern them from the signal that we would see if gravitational radiation was there we don't see any gravitational radiation yet we don't expect to yet we're not sensitive enough yet but this is a very important test of this of this method and this has actually happened much more quickly than I would have ever expected so I'm going to show you now laughs complicated plot this is one of these so-called power spectra again and I have two spectra here this is the normal kind of polarization and remarkably not so many years after we made the first resolved images of the temperature anisotropy we're now able to not just detect the polarization but to measure its spatial distribution on the sky and I draw your eye to the red data which is from bicep sister experiment quad and the black data which is from bicep and this is data acquired just in the last few years and the gray line this time is a model with no free parameters having measured the temperature and I saw trippy the theory predicts exactly what this should look like and you can see the agreement is really stunning so we really think we're on the right track let me also point out something completely amazing this line here and I didn't put one here but it would be here this is at a level now of 1 micro Kelvin one millionth of a degree temperature difference on the sky and we're still able to do these measurements and we have we don't have to to pay any attention to a from our own galaxy or anything else right that the the microwave background is so bright and so pure that we're able to now be looking for less than one part per million features in it and so far we don't see any signs of any trouble finally this is the Holy Grail this is the signal we seek what would it tell us if we saw that signal you know that signal was born in the very moment of inflation arguably the way we're thinking now when our observable universe was spawned from what I'm not sure and the amplitude of this signal will tell us something about the detailed physics of what drove inflation so we're really in a span of a few short years peeling things back to really ask some questions about what were the specific causes and origins of our observable universe now bicep has done a great job of digging down in here but it still has a ways to go and so this was a prototype experiment to test the method there's many more experiments that are going to be fielded soon so chao lin and myself and challon's youngest graduate student the the last in the generation of five that i showed you we're hard at work at a series of experiments now bicep2 just shipped a few weeks ago and it includes a new technology which has many more detectors and will allow us to push we hope that extra distance down just to show you I don't spend all my time being chair I occasionally a few hours a week I get to spend in the lab and this is bicep 2 just before it shipped down to South Pole and then similarly only with much more ambition Adrian and Bill and Paul have mounted a beautiful experiment called polar bear they have their own new very sexy detector technology which is going to provide them lots of sensitivity on the sky and a much bigger telescope which will allow them higher angular resolution and it's now being deployed to the Owens Valley and is it going to move down to Chile so I will end there and point out that this picture remains very prescient that we are in fact now digging back perhaps to a very small fraction of a second after the Big Bang beginning to perhaps make a measurement that tells us something about the physics of what was going on way back then the only thing the artists got wrong about this picture is he envisioned that this exploration would be done from the French countryside and I'm predicting it will happen either from Chile or from the South Pole I'll stop there I'll try to repeat the question right so the question is could we use neutrinos right to study the early universe and actually have a slide that shows that neutrinos would in fact penetrate that opaque wall they would take you back further though not all the way back to inflation the problem is neutrinos are arguably even more difficult to detect than gravitational radiation now it's really this this particular trick that some very clever theorists figured out that that the gravitational wave background if it exists will make this signature very specific signature in the microwave background that's what gives us hope of doing this now neutrinos I leave to to the next generation another question why did the early universe not collapse into a big black hole that's a very very good question so the answer is that is one of many questions right if it did maybe I should be more specific one of many interesting questions about our universe our universe many have noted seems fine-tuned in many ways to both lasts long enough and to be able to form atoms and planets and stars etc etc to allow the existence of life most specifically of observational cosmologists it's only slightly tongue-in-cheek right so if this event called inflation happened and it was some kind of nucleation some bubble right that popped out lord knows what exists before that then you might imagine that there were many such bubbles this is the so-called multiverse idea right so imagine now that you have some matrix of I don't know what but there's many of these bubbles going off right and you reach in and you pick out one of those at random and you ask what is this universe like right well we're not doing that experiment we're doing a different experiment we've already pre-selected the universe to be one in which we can exist okay so the answer to your question is for all I know most universes born out of an inflation event do collapse one microsecond later in a black into a black hole but we wouldn't have been around to ask this question so we happen to be in one right that has these properties right it may also be reassuring to you I had a slide here somehow it got left out but there's an artist concept of these various bubbles right it may be reassuring to you to know that Berkeley is approximately at the center of the observable universe so is Caltech near the questions variations yes okay this is a really excellent question you might suspect this was a plant but I don't think so so the question is a the observation that when we when we look at that screen and we see those those images right the kind of dull orange red red images that as I said we think now that those slightly more dense and less dense regions higher and lower temperature that those were originally born of quantum mechanical fluctuations in density at the sub nuclear scale that were then stretched to larger scales and in fact the theory makes a very specific prediction about the spectrum how much power there should be on large scales and small scales and that an initial spectrum that emerged from inflation was then processed by the phenomena that I described the acoustic waves and that's what created these degree scale bumps on the sky but if you go back it was more or less a white a white power spectrum and so there was I guess the answer to your question which was why you know how do they remain coherent is that the structures that we're seeing these degree scale structures are actually formed by the acoustic waves during the first few hundred thousand years of the universe right and and and that prior to that right you would have seen just a kind of a white noise spectrum okay okay right right yep we should talk more right here but I want to allow time for for one or two more questions if there are any yes it is specifically not significant right right because right but but people have stared at that and that that effect persists and you know it's it's interesting I should say that you know we've these experiments are continuing while these are continuing and our major thrusts now from the balloon born and the ground-based experiments is to look for this wonderful signature of of inflation there's yet another satellite that's been launched a few months ago called called Planck and it's up and it's working very well and it's going to measure the temperature power spectrum with really fantastic precision and we'll be able to make several other tests including you know sharpening up all of those error bars so yes we will narrow those down and it's it's conceivable that we could find out that the universe is in fact just not quite flat but I'm I'm betting not if I had to guess it maybe one more right since well first of all so the question is since we know how the universe was born can we create these conditions to create another universe fortunately we do not know how the universe was born where we're we're you know we're making progress there always be another question and and as far as we can tell what we do know is that the energy scales at which this event took place we're far far higher than anything that we can imagine ever creating which depending on your point of view is either disappointing or fortunate okay all right and maybe one very last question gravitational waves almost certain will I will gravitational waves exist we've seen that we've seen only indirect evidence of them but very beautiful experiment watching a pulsar spin down was awarded a Nobel Prize so that's pretty convincing evidence if LIGO does not detect gravitational radiation directly in the next five years I personally will be deeply embarrassed and in weather this different gravitation whether the gravitational wave background from inflation exists well that's the whole point if if we find it it's really smoking gun evidence that inflation happened however and I did downplay this aspect in my talk it could exist but at an amplitude which would make it very difficult for us ever to see it right so this is a really good project if you already have tenure and and Jamie Tolman will talk over dinner okay let's just stop there you

Channel: UC Berkeley Events

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Length: 77min 29sec (4649 seconds)

Published: Wed Nov 18 2009