9UNP0979SD_Eric_Wilcots_Transcript_WordPress
University Place 
The World's Largest Radio Telescope 
Eric Wilcots 
2/11/14 

- Good evening. Welcome to UW Space Place. This is our guest speaker night, and tonight we have Professor Eric Wilcots from the astronomy department at UW-Madison. Eric is a radio astronomer, and he's been involved for quite a few years now with this project called the SKA, which he's going to tell us about tonight. SKA and the future of radio astronomy. Eric. 

- Thank you, Jim. Thank you all for coming out tonight. 

It's a little chilly out there, but I'm glad you could make it. So, as Jim said, I do a lot of radio astronomy, and I've done radio astronomy for all my professional career. So I'd like talk a little bit about the next new big project in radio astronomy coming up. But on the way, we're going to cover a little bit of why we want to do radio astronomy in the first place, and then build up to the conclusion of the SKA. So here is a picture, and I'm not sure with the lights how well you can see it, but you have all seen this picture before. You go outside at night and what you have up there in the sky is this diffused pattern here of light which is the Milky Way. And if you are a careful observer, you can look towards the constellation Sagittarius, and you might realize that it's a little brighter toward Sagittarius. There seems to be a little bit more going on in the direction of Sagittarius. So astronomers in the late 1800s refer to that as the Great Star Clouds of the constellation Sagittarius, not really understanding what was going on in there. So this is a picture your eye would get. 

Optical light which your eye is sensitive to. If we look in a little bit more detail through an optical telescope, you might see a picture like this. Once you get pointed toward those great star clouds in the constellation Sagittarius, right there in the middle you see that bright glowing bit in here. And you see a bunch of other star clouds up here, high density of stars here, and then the dark regions which are now we know regions of gas and dust close to this particular part of the Milky Way galaxy. So, again, this is with an optical telescope. This is something that your eye would be sensitive to. With an optical telescope, this is what we see. When you use an optical telescope, you're primarily seeing the light from stars. So we are primarily tracing starlight, and the regions where we don't see much in the way of starlight is looking at the gas in between the stars. So let's take a little pause from that picture and go back in history a little bit to an individual named Karl Jansky who got his degree from the University of Wisconsin-Madison in the 1920s. 

He also played hockey. And I think he was probably maybe the last physics major to play ice hockey for the UW Badgers, but he did play ice hockey. So here is a picture of Karl Jansky in front of a very large device. This is one of the things that he got to work with when he left UW and took a job with AT&T, then known as Bell Labs in New Jersey. And he was given the task of trying to help understand the source of noise in some of the early communications equipment that was being developed then. There is a persistent little noise that kept coming in, and folks wanted to figure out where it was coming. So Karl Jansky's first job was to try to understand the source of this noise. The source of what was complicating the communications. So over time what he discovered is that the noise had a sort of seasonal pattern to it. That's kind of interesting. 

And then what he noticed is that it seemed that most of this signal, this unwanted signal, was actually coming from the direction of Sagittarius. From those great star clouds that we saw in the previous picture. And to jump ahead a few decades of radio astronomy, this picture here on the left is actually the same image that we saw back here but just taken with a radio telescope. In this case, taken with the Very Large Array Radio Telescope in New Mexico. We'll talk more about that in a second. So what you see here, nicely labeled to guide the eye, is this image is taken with a light with a wavelength of 90 centimeters. So very long wavelength radio waves. And what we are peering at here is actually the center of the Milky Way galaxy. And so Karl Jansky's discovery, coming from his effort to understand the source of noise in these early communication devices, was actually discovering radio emission from the center of the galaxy. And it was the first detection of radio waves that came from an astronomical object other than the sun. 

It was the birth of radio astronomy. And Karl Jansky is known as the father of radio astronomy. The Very Large Array Telescope, and I'll show you pictures of that in a little bit, is now called the Karl Jansky Very Large Array Radio Telescope. He is so famous that he has a fellowship named after him: the Jansky postdoctoral fellowship. But more importantly, he has a unit of measurement named after him. And so we measure the intensity of radio waves in units of janskies all because of Karl Jansky. So what we see here is, as I mentioned, the center of the Milky Way galaxy. A tremendously turbulent place with lots of radio emission coming in various shapes and looks like it's somewhat spiral. It's very, very complex. And this is all driven now by what we think is a massive black hole located at the center of the galaxy, and the emission is associated with the processes near that massive black hole. 

But that's getting a little bit ahead of the story. So we won't quite get there yet. So the other reason you want to do radio astronomy is this following comparison. On the left-hand side, you see an optical image taken with an optical telescope of the galaxy M81. A nice spiral galaxy not too far way. Relatively close to us. It's got a few neighbors. Above it is the galaxy M82, down below is the galaxy NGC 3077. Just the phone numbers. On the right-hand side, you see this same chunk of sky but now mapped in the intensity of the neutral hydrogen atom. 

So if I had a bunch of neutral hydrogen atoms with me, over time they would emit radiation, and it comes from the fact that a hydrogen atom has an electron and it has a proton. And occasionally, the electrons and the protons, their spins are parallel, and occasionally they're anti-parallel. And that switch leads to the emission at a wavelength of 21 centimeters, or frequency of about 1420 megahertz. So if I have a radio telescope, sensitive to radiation at a wavelength of 21 centimeters, I can map the universe in neutral hydrogen, which is the most common of the elements. So this is a picture on the right of the neutral hydrogen gas embedding these three galaxies. And so what's remarkable about this is that on the left-hand side we see what appeared to be three relatively isolated galaxies. Yes, they appear on the same part of the sky. They're probably relatively close to one another. But when we look in H1, when we look at gas, what we see is that these three galaxies are interacting. And that they have gone to some dance around one another that is now distorting and ripping the gas out of the different galaxies, dumping that gas into what we call the intergalactic medium, and really what we have here is a bit of a train wreck that's not evident when you just look at the stellar distribution. 

But when you look at the gas, you can make that distinction. So that's another reason we like to use a radio telescope. And here's another picture of, again, one of my favorite objects. This is M87 in the upper left. It is the central galaxy in the Virgo cluster. And so if you think about the solar system, our little solar system, we are orbiting in a little section in the Milky Way galaxy, and the Milky Way galaxy is part of a group of galaxies called the Local Group. That's our neighborhood. Those are our nearest neighbors. And the Local Group is sitting on the far outskirts and moving towards this massive thing, towards the constellation Virgo called the Virgo cluster of galaxies. Deep in the center of that is a giant elliptical galaxy called M87, also known as Virgo A, and what you see here is a picture of the center of Virgo A taken with the Hubble Space Telescope. 

An optical telescope so, again, we're seeing the stars. That is just in this little box down here. Coming out of the center of the galaxy if you look with a radio telescope, we see this wonderful jet coming out of the center. That jet reaches out here, so this distance here is about 400 parsecs. If we go up here, we're looking at close to a kiloparsec, and if we go farther out, we see this diffuse emission spread far beyond the boundaries of the galaxy itself. This is what we call an active galactic nucleus. Deep inside Virgo A is a supermassive black hole that's secreting matter, and it's secretes, it sends off these giant jets which then dump material and energy back into the intergalactic medium. And that's what we're seeing here in Virgo A. We see the same thing in this classic one. This is Cygnus A. 

And so in the summertime when you go out and you look at the stars and look up at the constellation Cygnus, what your eyes don't see is that there's an object there called Cygnus A, which is the brightest radio source in the constellation. That's the center of the galaxy. Giant jets coming out, dumping their energy out of these giant lobes. The analogy is shooting a fire hose against a brick wall. Why these stop, we're not quite sure. The density of the intergalactic medium must be high enough to stop the jets. But you can only see these jets, or primarily see these jets, looking through a radio telescope. So those are some of the reasons why we might want to build a radio telescope, to see the universe in a completely different light than we do with our eyes. So instead of looking at starlight that we do with an optical telescope, we are looking essentially at very high energy plasmas. Relativistic plasmas. 

These are particles moving very closely to the speed of sound in very strong magnetic fields, and they get these kinds of phenomena that we see here. Cartoon of what the inner workings of an AGN might look like. So you see the black hole there, which is nicely black in this image, surrounded by a disc of material that is probably falling into the black hole, and in that process these two jets come out in opposite directions of the disc, perpendicular to the disc. How those jets get columnated in such a tight, tight pattern, we don't really know and are in active research, but that is probably what's going on in the center of these AGN like M87 and Cygnus A. So good reasons to build a radio telescope because there's just different phenomena in the universe that we cannot observe with an optical telescope and are only visible with a radio telescope. And so here is the current best radio telescope in the world. This is a picture of the Jansky Very Large Array located in New Mexico. Has anybody been there? I know Jim has. So if you go, you fly into Albuquerque, you drive about 75 miles south of Albuquerque to a town of Socorro. 

It's right on the Rio Grande River. You head west from Socorro out into the plains of San Augustine about another hour west of Socorro you will come across the Very Large Array at elevation about 7,000 feet spread out over a plain. It is what we call an interferometer, and that is it's a telescope that works by combining the images from a number of different telescopes. There's actually 27 of these dishes. Each one of these is 25 meters in diameter. So it's astronomers being very clever, we call it a Very Large Array because it's an array and it's really big. This is a radio telescope and currently the best in the world. It was built on time and on budget in late 1970s. Opened up about 1980 and has been working every since, spectacularly, and doing some fantastic science. So the images I have shown you so far have all come from the Very Large Array. 

So here's an aerial picture of the Very Large Array. You can see it's on this old lake bed in New Mexico. It has this remarkable ability of actually changing its resolution. You might notice, if you have good eyes here, that there seem to be railroad tracks here. So the array is actually built such that each dish can be moved, and the -- will cycle through four different configurations over the course of 16 months, moving the telescopes, changing their separations because one of the remarkable things about doing interferometry is that the farther apart your telescopes, the higher the resolution image you can make. And so we can change the resolution and the sensitivity of the array by changing the positioning of the dishes. There are down sides to doing that. Your dishes are more spread out, you don't get quite as good image quality, you need brighter sources, but you can get much higher resolution. This is in the most compact configuration of the Very Large Array, what we call deconfiguration, where the dishes are actually very close together. And there's 27 of them, as I mentioned before. 

So one of the neat things about a radio telescope and about radio astronomy in general is that the primary source of noise that limits a radio telescope is all instrumental. It's all within the telescope itself. We're not really limited by the sky background. We're limited primarily by the instrument itself. So you can upgrade a radio telescope much more easily than you can upgrade an optical telescope. To upgrade an optical telescope, you really just need to get a new mirror. It's much easier with a radio telescope. And over the last five to 10 years the VLA has gone through a tremendous upgrade. So it's really now almost a brand new telescope from what it was. And the other thing that we can do because we're dealing with electronics, and it's all electronics, is that the more bandwidth we can look at, the more of the spectrum we can sample at any one time, the better our sensitivity. 

So here are just a few of the ways that the VLA has been upgraded over the last decade by the National Radio Astronomy Observatory, which operates the Very Large Array. There's a fantastic new correlator which has 262,000 channels. So what does that mean? That means that the VLA can take data and slice it into almost any number of ways that you could possibly want. And that's what the new powerful correlator can do. So it's a fantastic new telescope. It's been doing some great things, but it's even kind of limited in what we might want to do in the next generation. So we have the VLA. It's sitting there in New Mexico. It's been functioning for quite some time doing great science, but astronomers are greedy. 

We like bigger telescopes. We like more sensitivity. We like to push the frontier even farther. So on the optical side, we have gone over the last 50 years from 4-meter class telescopes to 8-meter telescopes to 10-meter telescopes, now we're building 30-meter telescopes. Getting bigger telescopes, more sensitive, collect more light. On the radio side, we need to make a leap from the VLA to the next generation to begin to do some fantastic new science. And so here are the main science drivers that keep radio astronomers like myself motivated and looking into the future about what great things we can do down the road. So the Cradle of Life, and all of these have passed through that process of vetting and coming up with clever names to make it somewhat appealing. So there's the Cradle of Life, the formation and growth of planetary systems, terrestrial planet growth, biotic and pre-biotic molecules. This is trying to look at Earth-like planets around other stars and begin to trace the formation of planets like our own Earth and to look for the first evidence of the biotic material that might be in the gas that makes up planets around other stars. 

Strong field tests of gravity. This goes back to Einstein and some remarkably neat physics, and we'll talk about that in a minute. Origin and evolution of cosmic magnetism. One of the neat things about the universe is that the universe is magnetized. There are magnetic fields everywhere. The Earth has one. The sun has one. Jupiter has a really big one. The galaxy has one. Stars have one. 

There's magnetic fields threading through the interstellar medium. There's probably magnetic fields threading through the intergalactic medium. We're not quite sure when the universe began to develop magnetic fields and how. And one of the neat things about radio astronomy is we actually have direct ways of measuring magnetic field in other stars, other solar systems, other galaxies, and the gas in between galaxies. So that's the origin of cosmic magnetism to be able to do that. Galaxy evolution and cosmology. This is big stuff. Everybody want to know how galaxies, like our own Milky Way, form. Part of the way of doing that is we need to measure the gas content of galaxies. Large redshifts, and we'll talk about that in a minute. 

And then lastly, the so-called epoch of reionization. The epoch of reionization goes back to the Dark Ages. Astronomers have these clever titles. If you think back of the history of the universe, at one point after the Big Bang, the universe is expanding, expanding, it's cooling down, and reaches a certain point where electrons and protons get together. And at that point the universe essentially become opaque. If you are a photon in that part of the history of the universe, you're not going to get very far. You're going to be absorbed by matter. And so the universe enters what astronomers call the Dark Ages. Now, as that expansion continues, the universe gets larger. At some point in that early history the first star or the first galaxy or the first source of ionizing photons turned on. 

And that begins what we call the epoch of reionization. When the universe began to light up again and those electrons became separated from protons and light could then travel freely through the universe. The universe now is mostly ionized. So light can travel across vast distances. So when did this reionization happen? What were the first sources of reionization? That's a key question that we're trying to answer. All right, so we're going to step through these, and please, ask questions if some come into mind. So we'll start with cosmic magnetism. Love that phrase. 

So if I look at a galaxy, and here's a famous galaxy, what you see in this picture, it's a fairly complex picture, but what I notice if you've got these sort of contours out here, and those are the contours that trace the intensity of the radio emission as measured by a radio telescope. You also notice these lines, you see a few of these lines in here, and those lines are showing us where the magnetic field in that galaxy is. The same type of magnetic field that we have around the Earth but here on a galactic scale. And what you might notice is that the magnetic field seems very well organized. As a matter of fact, the magnetic field seems to follow the spiral pattern that we see in stars and gas. How magnetic fields get to be organized is something that's actually at the heart of a lot of the research that we do here at UW Madison through our Center for Magnetic Self-Organization is understanding the origin of magnetic fields, how they become organized, how they grow to be on such large scales, and we're not quite sure how that happens. So one of the things that we can do with a radio telescope is actually measure the intensity of the magnetic field, and we can measure the direction of the magnetic field. So here's an example of how we can do that, and this is through something called rotation measures. You don't need to remember that. But imagine there's some distant object out here and that object is polarized. 

Your sunglasses might be polarized. And so that polarization, as that light passes through the intergalactic medium, it runs into something, some cloud of material. And the effect of that cloud of material is to change the angle of polarization. And so what we observe with our radio telescope is a different angle than what was emitted by the radio galaxy to begin with. And the trick is to be able to measure how that change in polarization changes over different frequencies. And if we can measure that, that is going to tell us something about the density and the magnetic field in this intervening cloud of gas. In this case, it's the material in between galaxies in a cluster. Okay? So one of the neat tricks we're going to do is we're going to measure this change in the angle of polarization as a function of frequency. It's a bit of a neat trick, but if you've got the right radio telescope, you can do it. 

And it tells you about the magnetic field in the intervening cloud of gas. That is how we can probe some of this gas in between us and much more distant objects. So a lot of words on here, but the main idea is to be able to measure the strength of the magnetic field in galaxies that are very, very distant. So galaxies when they're quite, quite young. That's one of the ideas. To see when magnetic fields actually get started and to give us three-dimensional view of the magnetic fields in the universe on the largest of possible scales. We can do that once we have the right radio telescope. So here's an example kind of putting that in mind. There is a map there of galaxies. Smooth just to show you that there are some areas that have a lot of galaxies. 

There's some areas that don't have very many galaxies. And if we do the same thing with these so-called rotation measures, as I showed you in the previous slide, we can also get an idea of how the magnetic field changes with that density of galaxies. And we can trace magnetic fields on very, very large scales. Now, how the universe gets to make magnetic fields on these huge scales, we're not quite sure yet. This is something that we really want to know. So we're going to be able to get lots of magnetic fields with the SKA once it's built. Okay, so let's go on to something called gravity waves, which is kind of fun. It's kind of like surfing. The idea behind gravity waves is something that actually comes from general relativity. And the notion is if I have an event, a very dramatic event, it will essentially send ripples through space time, so-called gravity waves. 

And the idea is that if I can measure those gravity waves, then I get a sense of this dramatic event. So an event, for example the merging of two black holes would be a dramatic event that would generate a lot of gravity waves. And astronomers are trying to approach this in a couple different ways. There's a project called -- which is being built down in Florida, I think, that actually uses lasers and optical light to try to measure these ripples of gravity waves. Very, very challenging measurement to make. Radio astronomers are going to use something a little bit different, and they're going to use pulsars. Pulsars are these compact objects that spin very, very rapidly, and as they spin, there's a little beam of light, kind of like a lighthouse, and as that beam points in our direction, we will detect the signal. And because they're spinning very rapidly, they become very, very good clocks. So the idea behind this experiment is to identify lots and lots of pulsars. They're the remains of stars. 

They're neutron stars. So the remnants of stars that have lived their lives fully and now left behind these neutron stars. So if we can detect lots and lots of pulsars and time them very, very accurately, we can detect the presence of gravity waves. So what you see here is some event over here that emits gravity waves. And you can see the gravity waves travel through space and they encounter this particular pulsar. Now, they're going to affect that pulsar in slightly different ways than they might affect this pulsar or this pulsar or this pulsar. And the timing will be different. And so here on the Earth what we're going to do is be able to observe all of these pulsars and then be able to detect the presence of gravity waves by the effect that it has on that pulsar there in changing the timing of the signal from one pulsar. But we need a whole network of these things. And you detect pulsars with radio telescopes. 

So the more sensitive our radio telescope, the more pulsars we can detect, the better our pulsar timing will be. And the idea is to build what people call a pulsar timing array. So you have this array at 10,000 pulsars. They're constantly being monitored for variations in the timing of their signal will show us that we've got gravity waves moving through the Milky Way. Now, if we have enough pulsars and you detect a signal, you can then use that array to figure out what the source of those gravity waves might have been and then go back and see what actually is emitting the gravity waves. So the idea is to get lots and lots of lots of what we call millisecond pulsars to be able to build a pulsar timing array. So here's an example of two objects that should be spinning around. As these two compact objects spin around, they'll be emitting gravity waves, and you can see the schematic here of those gravity waves going through space. The pulsar sort of rides that gravity wave, that affects the timing of the signal, and we measure on Earth the change in the timing of the signal from different pulsars to be able to measure the amplitude of the gravity waves. If we can do this, that's going to be really cool. 

Whoever gets to do this is probably getting a Nobel Prize. That's my bold prediction. So here's sort of another schematic of the Earth there in the middle of this cosmic space time with pulsars all around us and we're measuring these ripples in space time and our own galaxy being generated by gravity waves as they course through the intergalactic medium. And that's something you can do, once again, if you can get lots and lots of pulsars, and the way to do that is to have a really good telescope that can detect the very faint pulsars but detect lots of them at the same time. Galaxy evolution. We want to know how do galaxies get their gas. You can think of galaxies, like the Milky Way, as factories, machines, that have the purpose of converting gas into stars. That's what a galaxy does. It takes gas, converts that gas into stars. And so we can ask ourselves the important question for galaxy evolution is how do galaxies get their gas? 

Is it a one shot deal? You get a supply of gas, you convert that into stars, and then you're done? Is there a constant stream of gas into galaxies? How might stars kick some of the gas back out? And so it is that evolution, that cycle of how gas gets in and out of galaxies that's really interesting for understanding how something like the Milky Way has evolved over time. I showed you early on a picture of the M81 group. The key part of the gas is looking at neutral hydrogen, and that's what we need a radio telescope for. So we can look at all things. Did gas get in through mergers? Sort of mergers and acquisitions. 

Is is accretion from shockwaves coming in and depositing gas in the galaxy? Is there blowout of gas? All of these things we can measure with a good radio telescope looking at the neutral hydrogen content of galaxies. So here's a picture. There's a galaxy. I want you to notice here, this is sort of a schematic of us and M31 that there's lots of clouds of gas around M31 that we've recently detected using the Green Bank Telescope in West Virginia. And you can see the galaxies seem to have cloud of gas and filaments of gas surround them. Whether they're flowing in or flowing out, we're not quite sure. But they do seem, it's more complex than just saying you get a one shot deal, a one shot supply of gas, process through that gas and then you're done. So galaxies are very, very complex machines. 

So here's just a bunch of pictures showing various measures of H1 and galaxies nearby. It gets really complicated. And what it shows is that the galaxies have been torked and affected probably by nearby dwarf galaxies, maybe by in-falling clumps of dark matter. All sorts of things that can distort the neutral hydrogen content of galaxies. We see plenty of examples of that in the nearby universe. The goal of the next generation of radio telescopes is to be able to do a giant survey to get a hundred thousand or a million galaxies and to build up enough of a data set in order to be able to make conclusions about how galaxies are evolving. So, what do we need? We need to measure the evolution of the H1 content of galaxies maybe out to a redshift of 2. So, what does a redshift of 2 mean? That's when the universe was about a third of its current age. 

So a young universe, only four billion years old or so. To look back at galaxies as they were early on in their stages of formation to understand how those factories were put together. That's what we want to be able to do. You need a big telescope to do that. We want to look at how gas falls into galaxies like our own Milky Way. We want to get a complete census of the H1 around us and around nearby galaxies. And we want to understand the effect of the environment on galaxies. Galaxies live in an environment. It can be turbulent. As we see in the nearby universe, it can be affected by other galaxies, it can affected by the density of the intergalactic medium. 

We don't really know the effect of the environment on the evolution of galaxies. We know it's important, but we're not quite sure how important it is and what the processes are. That requires measuring the H1 content of galaxies, a lot of galaxies, all at the same time. And we want a fine scale structure of the interstellar medium where galaxies are making stars to understand that process of star formation. As I say, astronomers are greedy. One of the things we're doing, and this is some fun we're having with our colleagues in South Africa, is a project called LADUMA. And it is, the name comes from a South African word which reflects the celebration that you might associate with a soccer match. Those of you who watched the World Cup in South Africa a few years back, you might have seen these nice horns that they've got down there. So the idea behind LADUMA is to take this new telescope they're building in South Africa, point at one part of the sky for a very, very, very, very long time, and see what we can find. And push out as far as we can in measuring the H1 content of galaxies. 

So our idea is to try to get out to a redshift of about 1. Maybe get about 10,000 galaxies as a precursor for what the SKA is going to be able to do. Hopefully we'll get started with this project in the next couple years. We've actually already started a similar one using the VLA that is actually currently ongoing. Cradle of Life, everybody wants to find planets. It is the biggest change in the discipline over the last 10 to 20 years. What I tell my students, and I don't want them to think that I'm that old, but I tell them when I was their age I knew of exactly one solar system. We happen to live in it. Now we know of about 2,000 solar systems, nearly 4,000 planets. It's around those numbers. 

A huge change in the field and in trying to understand these planets, and the diversity of architecture of planets is something that we really, really need to do and understand how planets form. One of the neat things you can do with a radio telescope, and this is actually kind of interesting, early in the stage of the formation of a planetary system there comes a point where you're putting together terrestrial planets like the Earth. That process is very energetic. And with a good radio telescope, the proper radio telescope, we should be able to observe and detect terrestrial planets in formation in very young planetary systems to really see how that process might work. So here's just a nice picture of what another planetary system might look like. The reference to measure magnetic fields around extrasolar planets haven't quite gotten there yet. We just need more sensitivity. So understanding the formation of Earth-like planets is something that we really, really want to be able to do. And the other neat thing you can do with a radio telescope is look for molecules. Most molecules have a lot of their transitions in the radio and millimeter part of the spectrum, and we can detect a lot of exotic molecules, a lot of pre-biotic molecules, using a radio telescope to begin to understand when and where some of these complex molecules might form in association with new planetary systems. 

Okay? So, very, very, exciting stuff looking at the cradle of life. And, again, you want a big radio telescope to be able to do that. Epoch of reionization. So now we're going to go from nearby, we're going to go very far out. We're going to go back to nearly the beginning. So here's a nice schematic put together by colleagues at NASA of the history of the universe, or at least the part of the universe that we can see. So here we're going to start on the left-hand side of the diagram with something we call inflation. The Big Bang occurs over here. So we've got time moving to the right. 

So the universe expands greatly and we see that imprinted in the microwave background, the cosmic microwave background. And then the universe goes through some, as I say, some period what we call the Dark Ages. And that is when electrons and protons recombine, and so the universe is dark. And if you're a photon, you don't get very far. And we can't see that. We don't know what happens during this age, but something happens back here. The very first stars turn on and begin to ionize the universe, and from there on, we see the evolution of the universe take place as we can observe it with our current telescopes. So part of the evolution of galaxies that I talked about before is being able to understand what galaxies looked like back here when the universe was half of its age or maybe when the universe was a third of its age to understand how galaxies got put together, how large scale structure got put together. But we also want to go back and understand this epoch of reionization. What were the very first objects to turn on early in the universe's history? 

That ended the Dark Age and led to the universe that we can observe today. And that's one of the Holy Grails of modern astronomy to be able to get back to that epoch of reionization and look at it. So one of the things that might happen, say, well, I had an electron and a proton that got together, so I've got a hydrogen atom. And remember, hydrogen left to its own devices has this nice transition to 21 centimeters, 1420 megahertz. Now the problem is I'm looking at the universe when it was one-tenth or one-eleventh its current age, and so the redshift associated with that, it's a redshift of 10 or 11, and so that H1 line, that neutral hydrogen line that would normally show up at 1420 megahertz is now redshifted way down to 80 or 70 megahertz. And for those of you that have turned on your radio lately, you might notice that that's a pretty crowded part of the spectrum. But we want to be able to probe the universe at those very, very low frequencies to look at what happens to hydrogen early on in the history of the universe. And now if my movie will work, oh good. This is going to be a simulation of reionization done by Steve Furlanetto, who's a professor out at UCLA now. This was done while he was still at CalTech. 

So what you have here is a picture of the universe early on, and what you're going to see happen is sources of ionization turn on and we will start blowing holes into the early universe. So consider this the Dark Ages. And the simulations will tell us over time things happen, and you see the universe begin to become ionized. And we're left with a structure in the universe, a large scale structure that we now see. Let's see if I can replay this. We can go back to the beginning. We're in the Dark Ages, and you see these dark regions. We're going to call those ionized regions. Something turns on to begin to ionize the universe in pockets, and they grow as more and more things turn on. So the idea behind the next generation radio telescope is to be able to go back and capture the universe, I was going to try to pause that there. 

We'll try that one more time. So, there. And there. To get the universe and get a map of what the universe looks like during the epoch of reionization. And the trick is to be able to detect neutral hydrogen redshifted down to low, low frequencies so you're actually mapping the universe as it looked very, very long ago, early in its history, to capture this epoch of reionization, to figure out what the first sources of ionization were. And that's one of the goals in the next generation radio telescope. Okay, so there's some big science goals. Astronomers, as I say, have a huge appetite. We're greedy. We want to have this big telescope. 

And so the idea came across, let's build a telescope that will accomplish some of these things. Well actually, the very first idea back before, we'll call it 20 years ago, was the notion of what would it take to detect the neutral hydrogen content of the Milky Way galaxy at a redshift of 2. We'll look at the Milky Way as it looked eight to nine billion years ago. And what you need then was roughly a square kilometer of collecting area. You can do the math and figure out what that is. So the VLA, for example, is 27 25-meter dishes. It's a far cry from a square kilometer of collecting area. And hence the name, the square kilometer array, came out of that idea. And so over time it grew, and this slide sort of shows a bit of the growth of that because, again, astronomers are a little bit greedy, and so all the sudden this telescope that was envisioned for the purpose of finding a Milky Way galaxy at a redshift of 2 became a multipurpose instrument that would cover all of the science that I just described. So you needed build a telescope that worked from a hundred megahertz out to 25 gigahertz. 

The hundred megahertz to give the epoch of reionization; the 25 gigahertz to look at terrestrial planets around nearby stars. And it has to span all of that. The problem is you can't do that with a single bit of technology. The dishes of the VLA don't work that well at a hundred megahertz. They don't point quite well enough at 25 gigahertz. So you're going to need to build different technologies. So over time we realized that the project was going to be more complicated than what was originally devised. And so the idea was then to break it up by technology. Basically use a dipole to measure the low frequency things. It's a fancy dipole, but it's an old fashioned dipole to measure low frequency radio waves. 

At the higher frequencies you want smaller dishes that can point very, very accurately. So it ended up being a number of different configurations. And then you want to sample the universe in a variety of spatial scales, and so you want to spread out your instruments over large distances. So what this translate into is the notion that to build a square kilometer of collecting area to do the science that we needed took, for example, about 4,000 12-meter dishes spread out over distances of, say, 3,000 kilometers. That is what the square kilometer array sort of grew into as a vision for what the instrument might be. It's the VLA on steroids. Okay? So we went through a process, a very long, long process of designing the capabilities, what we wanted the telescope to be able to do, and then trying to figure out where to build a telescope like this. And so when I first got involved in the project, a group of universities in the United States, we called ourselves the US SKA consortium, got together and thought about whether or not the United States should bid to be a host for the SKA. Could we build this square kilometer array in the United States? 

We ran into a couple problems if you try to do that. One, the radio interference environment is not great here. The big problem with radio astronomy these days, and I contribute to this problem, I admit, I have a cell phone. Anybody else in the room have a cell phone? Those things generate a lot of radio interference. And all of our communication technology does. So the biggest problem with radio astronomy these days is radio interference, man made radio interference. From TV station satellites, cell phone towers, communications in general just generates a lot of noise in the radio part of the spectrum where astronomers would love it to be completely blank left for our purposes just to go study neutral hydrogen. So you like to build this in a really what we call radio quiet place. Radio quiet means not very well populated. 

And so the United States does not fit into that category. There's also the not insignificant problem is that if your telescope requires 4,000 12-meter dishes and you're going to put them all over the United States, you cannot transport 12-meter dishes across the United States. There are far too many bridges on our highways. To think about having some factory that's cranking out 12-meter dishes, you plop them on a truck and you drive them on a truck across the country, they're not going to make it through all those bridges. So this actually becomes a logistical problem in trying to build something like this in the US. So we did bid for the site. So the initial countries that bid, there's a process. Countries put together bids, and in the end two countries made it to the final round: South Africa and Australia. And then after another fairly lengthy process of site testing, monitoring the atmosphere, etc, lots of political factors as well, it was decided that the telescope, the SKA, which once was envisioned as one telescope to do all the science, was going to be sited in both South Africa and Australia to do different aspects of the project, for good reasons. Because one of the other challenges that one would like to be able to do, to do some of the science that I talked about, is sort of right in here. 

If you want to measure the H1 content of a million galaxies, if you want to get a sample of 10,000 or 100,000 pulsars in the Milky Way, if you want to map the epoch of reionization, you need to look at a lot of sky. And so you want your telescope to instantaneously be able to look at large swaths of the sky, and that drives us towards new technology to put on the telescope to get really, really large field of view instantaneously so we can see all these great things. So here's a schematic of what the SKA might look like. What you see in the white are little dishes, 10- or 12-meter dishes. The blue are these new fancy tiles that the Europeans are making to do the low frequency science. And the idea was to embed them together, spread them out in a nice spiral pattern, and make the square kilometer array. This was what we call the reference design at the time. And so here is a movie now of what things might look like in Australia. And what you'll notice, if you fly over these little circles on the ground, those are the low frequency detectors. Those are the detectors that will be able to map the epoch of reionization. 

Spread out in these circles over hundreds and thousands of kilometers centered in western Australia. And if you have ever been to western Australia, you probably increased the population density dramatically by just showing up because there's not very many people there, and it is a beautifully radio quiet part of the world. So western Australia will host the lowest frequency component of the SKA to map things like the epoch of reionization. And here's sort of an older schematic of what we think, media not found, oh no. It worked before. I will have to skip that then. I apologize. So we'll go back to, do I have another movie here? No. We'll go back to this picture. 

So this is the landscape of western Australia. So the place to build the telescope. As I say, you want it to be radio quiet, which means not very many people. You would like it to be really, really flat. You don't care too much about elevation. So unlike optical astronomers who want very high elevation sites to get above much of the atmosphere as possible, radio astronomers are a little bit less concerned with elevation. Yes, water vapor is an issue. We'd like to be fairly dry to minimize the amount of water vapor above us, but primarily we want a stable ionosphere. And so you're not going to get above the ionosphere, so the elevation doesn't matter as much. So a site like western Australia is fine. 

The South African site is located in northern South Africa in a place called the Karoo, but it will have dishes spread across all of South Africa, including the neighboring countries Namibia, Botswana, Madagascar. So it will be across a number of countries in South Africa. So the current state of the square kilometer array is that construction is starting to take place on the precursor telescopes in South Africa and Australia to build almost phase one of the SKA to get ourselves on a way to building the instrument. It will probably not be fully constructed until the middle of the next decade. Now, if you want to buy the SKA, you're feeling a little flush, stock market's gone up a bit, might have a little extra spending money, the price tag is probably about $1.5 billion to $2 billion to take care of the SKA. And so the current status is that there are a number of countries, and unfortunately the United States is not part of the partnership now that is building the SKA, that are led by South Africa and Australia with contributions from Canada, many of the European countries, China, India, New Zealand, I'm going to miss a few I know, but those are the main players right now in designing the SKA and designing the instruments that will be built in order to do the science that I talked about. So I'm going to end now with the other reason you build a new telescope. And this quote is borrowed from somebody famous who probably borrowed it from some other people. And this is the notion about the unknown. If you look back at history at every telescope project that has been proposed, there has always been a science case for building the telescope. 

Astronomers have always gotten together and said we want to build a telescope because we want to investigate X, Y, and Z. But once that telescope is built, its biggest contribution is generally something that you hadn't thought about before. Something that you did not expect, did not anticipate and it goes beyond what you planned for. And that is the beauty of pushing out into the new frontier with new technology. And so we want to talk about the unknown. And this is: "As we know, there are no known knowns. There are things we know we know." And what I've described in the science is actually part of the things we know. We need to test things, but we know about gravity waves. We know the galaxies evolve. 

We also know there's some things that we do not know. We don't know how gravity waves are generated. We do not know how the universe was reionized. We know it was reionized but we don't know how. So things that we know we don't know. But what's really, really neat about building a brand new telescope is what you don't know that you don't know. So the things out there that we have simply not thought about, we have not anticipated that are essentially beyond our imagination right now that a new telescope like the SKA will --. And that's going to be the exciting part when that telescope turns on and we discover stuff that we just had not thought about before. And that's when the fun comes in getting to do the job that I get to do. So I'll end there and be happy to entertain any questions you have. 

Thank you very much. 
[APPLAUSE]