Horizon, Host: Ted Simons

January 23, 2014


Host: Ted Simons

Krauss on Science


  • Arizona State University physicist Lawrence Krauss makes his monthly appearance on Arizona Horizon to talk about the latest in science, including how the Hubble telescope is using gravity to help it capture some pictures of some of the earliest galaxies in the universe.
Guests:
  • Lawrence Krauss - Physicist, Arizona State University
Category: Science   |   Keywords: science, krauss, physicist, gravity, telescope, universe, galaxies,

View Transcript
Ted Simons: Good evening. Welcome to "Arizona Horizon." I'm Ted Simons. Once a month ASU's physicist and best selling science professor updates us on the latest space and science news. Our conversations include how the Hubble space telescope is using gravity to capture increasingly distant images. Good to see you again.

Lawrence Krauss: Great to be back as always.

Ted Simons: We have a lot to talk about. From a distance, for the layman, this sounds fascinating. The Hubble telescope is, what, using galaxies for magnification?

Lawrence Krauss: It's neat. It's at once a demonstration of the fact that space is curved in the presence of matter and at the same time it allows us to probe the universe on scales we couldn't do before. It's based on a phenomena Einstein first proposed in 1936 but never believed to be observable. Einstein showed gravity is a really just a manifestation of the fact that matter and energy curve space. That when you put matter and energy in some region, space responds dynamically by expanding, contracting and curving. He realized that fact made him famous in 1919 when he proposed that light itself will bend around massive objects because space is curved and light is traveling in straight lines so the -- through the curved space. In 1919 astronomers looked at a total eclipse of the sun and saw stars that they shouldn't have been able to see that were the sun's blacked out and the stars should have been behind the sun but the light was curving around the sun and they could see the stars. In fact the amount of bending was exactly what Einstein predicted. He really wasn't famous among the public until then. He was famous among the scientific community but that launched him into stardom. It was right after the First World War, and it was a British expedition validating results of a German scientist. It was this beautiful --

Ted Simons: Gotcha.

Lawrence Krauss: It had all the earmarks. He became famous overnight 1936 he found a big distribution of mass with a source of light behind it rays can bend around both sides. They come together and they can be magnified like my glasses magnify light by bending light rays in and magnifying things or like a cut glass goblet. You see many images. He realized space itself due to the presence of massive objects could act like a lens. It could magnify and distort objects behind it. He was thinking of a star. He wasn't very knowledgeable astronomically. He said a star will do that but he calculated things and the effect was so small he said it would never be measurable. Almost at the same time another well-known astronomer said, no, you missed point there are galaxies containing billions of stars. Those would produce an effect that might be visible. About 20 years ago for the first time a big galaxy was observed to bend the light of a distant quasar. Galaxies are maybe a billion light-years away. Distort the light from a very bright object, a quasar, one of the brightest objects in the sky, it would distort the image. Two different images were seen and it was realized they were different images of the same quasar. The first observation. Since then it's become more prevalent. We have looked at objects. Now clusters of galaxies, the biggest bound objects in the universe, have been used to observe the same phenomenon. There's a beautiful picture online of a cluster of galaxies, maybe billion light years away. Amidst that cluster you'll see these weird blue things. Those are multiple images of a single galaxy looking -- located another billion years behind the cluster that would never have been observable but it magnified the image. First that demonstrates that space is curved. Second, we can use that to weigh the cluster of galaxies. We can say how much mass must there be in the cluster and where is it distributed to produce the image you see? Now we're turning it on its head saying, that's okay for weighing clusters but we can use the clusters. Astronomers have been looking at two different ones. Behind them galaxies are so abundant in the universe if you look at a cluster 3 billion light-years away, you might behind it might exist three or four thousand, galaxies that are normally so dim you would never be able to see them, but with the galaxy you can use it as a telescope. Now astronomers are observing these dim galaxies until the earliest galaxies ever formed because this cluster is brightening them by a factor of between 20 and 100. We're learning not just about the cluster but use the curvature of space to make a cosmic telescope to peer out at the most distant galaxies that we can see. Until we have the James Webb space telescope this is the best we have.

Ted Simons: What's this other telescope going to do?

Lawrence Krauss: The James Webb space telescope is now being built. It's literally going to replace the Hubble telescope. It's going to look at frequencies of light to be sensitive -- it's much bigger, much more light collecting power, it's going to look at the first galaxies that ever formed, what we call the first light of the universe. The universe was dark until the first stars formed the universe is dark. Eventually we think between a few hundred million years and a billion years after the big bang it caused them to form. In the interim this gives us a glimpse of those objects we never would see otherwise.

Ted Simons: This gravitational lensing, how far back have we seen prior to this, what has this taken us back to? What's the most distant thing we have seen?

Lawrence Krauss: Well, it actually every month it changes. Astronomers are watching their telescopes. We have seen back probably to the oldest galaxies and probably around nine to 10 billion years back in time. The universe is about 13 billion years back. Maybe 11 billion years back. These galaxies we're seeing are right around that time. The James Webb space telescope will get us further, but we're seeing objects at least 10 billion light-years away. Think about that. That means the light left those galaxies 5 billion years before our sun and earth even formed.

Ted Simons: Not only that the light we're seeing is so long ago -- who knows what's out there now?

Lawrence Krauss: We're doing cosmic archaeology. These additional aids we're able to appear further, learn about the birth of our universe, which is of course what it's all about ultimately.

Ted Simons: It's also about black -- talking about black holes a lot --

Lawrence Krauss: There's new stuff on black holes.

Ted Simons: Sounds like star trek. Like something is eating up something else.

Lawrence Krauss: Exactly. It's a cosmic lunch. Maybe not a free lunch but a cosmic lunch. We have talked about black holes but there's exciting news that just came out. There is a black hole at the center of our galaxy, a large one, probably about million solar masses. We talked about the fact that we can't see it directly but what's amazing to me, and you should go online and look at these movies, over 20 years astronomers have observed stars orbiting this dark spot and you can't see anything but they are moving around so fast and so close there's no object you can see, we are pretty certain it must be a black hole. That's great but what's really neat we would like to see what happens -- black holes are among the most energetic engines of light in the universe. It emits huge amounts of light when stuff falls into them. Fees quasars we think are large black holes swallowing things. We want to see up close and directly a black hole swallowing stuff because these stars are just orbiting around the black hole. What's been observed by some telescopes on the ground is a cloud of gas about three times the mass of the earth that's falling towards this dark spot at the center of the galaxy. Sagitarrius it's called. It's been falling towards it. Now if looks -- it looks like within the next few months the gas cloud is going to fall in. The effect has been observed. Spaghettification happens. Spaghettification is the fact that as you fall into a black hole the first thing has happens since your feet are closer your feet experience a greater force and you get stretched out. Eventually pulled apart like spaghetti. You wouldn't want to do it necessarily but this gas cloud is doing it now. We can already watch it being stretched as the front of the gas cloud is experiencing a greater force than the back of the gas cloud and we think, at astronomers think within a month or two or three this will actually fall in the black hole and we'll be able to see when the stuff falls in and shines. You have this telescope watching the gas cloud. Then another telescope called swift is looking at x-rays from -- staring at where the black hole is. As the gas cloud falls in, presumably you can watch the black hole light up and we'll learn what happens as constitutional falls? Not only that, apparently they are setting it up so you can watch online. You can sort of daily watch --

Ted Simons: Is it the kind of thing you can put your feet up and watch or do you have to be patient?

Lawrence Krauss: You would have to put up your feet and be patient. It takes place over a while. Bring a big TV dinner. Over each day you will probably see spurts of light emitted by the black hole as parts of the gas cloud fall in. It's really I don't know of another example directly in real time where we have been able to watch stuff fall into a black hole.

Ted Simons: You see if it changes the nature of the black hole.

Lawrence Krauss: Maybe. But we won't be able to see that much because the black hole is a million solar masses. It's not going to change much.

Ted Simons: Like eating a peanut.

Lawrence Krauss: It's going to light up the dark. Around the edge of the black hole it will fall in and that will be really important for us because as we try to think about how to learn about black holes we need to understand what the process is of stuff falling in. We have gravitational wave detectors looking for black holes swallowing stars and other black holes. All of that last-minute stuff, all of the action happens in the last few seconds as stuff falls in and a lot of it is difficult to predict theoretically. What you would like is observation.

Ted Simons: Is the black hole sitting there like a Venus fly trap or is it moving, is the gas cloud moving toward the black hole?

Lawrence Krauss: It's like everything. The black hole is near the center of our galaxy, relatively stationary. It's moving a little bit as our sun is, as the earth moves around it the sun moves a little bit in response, but the black hole is more or less stationary. It's not quite at the center of the galaxy but it's close. The gas cloud is literally falling towards it. It's already experiencing the direct gravitational attraction.

Ted Simons: The gas cloud is minding its own business, got too close. I gotcha. Before we let you go, I understand there's a space classic ready to launch a probe on to a comet.

Lawrence Krauss: This is the Rosetta spacecraft. It's already been getting slingshotted around different planets but it's been set up to eventually try and land something land on a comet, which is amazing because comets are very -- they may be a kilometer or two across, three, four, ten, but they are not very heavy so the gravity is very, very weak. The neat thing about this is people have designed this, they are the same ones who more or less designed Toigan's probe, with the Cassini satellite, which launched a probe which landed on Titan. You may remember a few years ago. Because it's so far away you can't control in real time. It takes hours fort signal or many minutes for the signal to get back. So the same thing is going to happen in a few months, maybe by November of this year. It will close enough, four kilometers away from the comet if it all goes well, it's going to launch not a bread box size object but something smaller than a car that's going to try to land on the comet. It all has to be done by remote control because it's so far away in real time the controllers here on earth can't do it so they have to keep their fingers crossed. It's going to try to land on the comet and learn about the comet. We want to learn about comets because they are our ancestors, if you wish. The objects that give us direct information of what the solar system was like when the earth was formed. The primordial ingredients. They come from the outer solar system, and that material has not been processed since the time the solar system was formed. The water in these comets was there about 4.5 billion years ago when the solar system formed and some of that is like the comets that filled up our ocean. We want to learn about the primordial side. In these comets there's not just water, but there's organic molecules, the basis of amino acids. The seeds responsible for the formation of life on earth. We want to learn the formation not just about life on earth but the origin of ourselves, we want to measure comets. It's such a difficult thing that if it doesn't work it won't be surprising but I would hate to be one of the controllers who built this, waited ten or eight years, you don't now until after the fact if it's landed or the whole thing has gone astray.

Ted Simons: I imagine it has to land at the right time. If it gets too close to the sun we know what can happen.

Lawrence Krauss: They are trying to get there early enough so things don't evaporate but late enough so we can watch that process as the gases and volatiles are emitted from the surface of the comet. By the way, it validates something else I always say, which is the way to explore space to do science is without humans. We wouldn't be doing that with a human right now. No way that's going to happen. As difficult as it is to hope you can manipulate these machines from a distance, so far we have been able to do it and I'm rooting for this Rosetta.

Ted Simons: Once again, fascinating stuff. Good to have you here.

Lawrence Krauss: Great to be back.

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