Science Matters with Lawrence Krauss

Feb. 17, 2016

Transcript:

Ted Simons: It's one of our most popular segments. Each month we welcome best-selling science writer and ASU physicist Lawrence Krauss to discuss the latest. The discovery last week of gravitational waves. Here to explain why he and other physicists are going nuts over the news is Lawrence Krauss.

Lawrence Krauss: And why TV journalists are going nuts.

Ted Simons: I don't even know why I'm excited but I am.

Lawrence Krauss: Must be the waves going through your head.

Ted Simons: Gravitational waves discovered. What are we talking about?

Lawrence Krauss: It's one of the most monumental discoveries in recent times because it's opened a new window on the universe. We look out with telescopes, we're looking at light waves, right? When Galileo first looked through the telescope 400 years ago he discovered things that changed our picture of the universe. Later we discovered radio waves. We could turn radio telescopes up and discover new things. The afterglow of the Big Bang explosion which enforced the fact that there was a Big Bang. What we have done now is open a new window, not in light, electromagnetic waves but gravitational waves. I'm hoping here we can really master the subject and give you a quiz afterwards. Einstein told us that because space is curved in the presence of matter, matter causes space to expand, contract, curve, then if matter moves around like my arms are moving now, there is a disturbance in the matter of space, and that disturbance propagates like a ripple in a pond at the speed of light. That disturbance in space is a gravitational wave. When it comes through this room, the size of the room changes back and the forth. It goes in and out like that, like that. It's happening now. Even as we sit here this room is changing in size although you can't notice it because it's imperceptible.

Ted Simons: I thought gravitational waves were always thought to be there.

Lawrence Krauss: They did -- thinking things are there and seeing them are two different things.

Ted Simons: This is actually discovering?

Lawrence Krauss: Einstein predicted them almost 100 years ago in June of 1916, so in June 100 years from the time that Einstein wrote down a paper saying if gravity -- if my general theory of relativity is correct it's taken 100 years to see them directly. We have not only confirmed in another way general relativity but a part that we never could have measured before. So we're testing general relativity but using these as tools to see the rest of the universe. Interestingly, in the interim Einstein recanted and said he didn't think they existed in 1937. He was wrong and happily submitted a paper to a journal and they rejected it, which caused him great consternation. Before he could resubmit it he discovered the error. It never really -- you might say why 100 years.

Ted Simons: Why 100 years?

Lawrence Krauss: Because in fact in order to discover these things we have to have the proper technology and proper theory. Because general relativity is incredibly complex. To estimate what's going to happen when two massive black holes we have used techniques, numerical techniques that required supercomputers. Those didn't exist 30 years ago, so those were necessary now to be able toll predict what it will be and as we talk about the device itself could never could have been built 30 years ago. This is about as soon after Einstein as we could have detected them and boom, we detected them within an hour after the machine turned on.

Ted Simons: What exactly was found? These two black holes. We have video of this.

Lawrence Krauss: Let's go to the first video. It's an image of artist's reconstruction. There's two black holes. The event that was seen occurred about 1.3 billion light-years away, so it happened 1.3 billion years ago. Two massive black holes each more than 30 times the mass of the sun were orbiting. The space behind them is doing strange things, because space is being warped. The light from space is being warped around them and then, zoom, those two holes come together in less than a second and merge into a much bigger black hole. Let me say one thing about this. Even if we don't get to the other stuff this is amazing. You have to think what happened in the universe that we saw? One black hole was 36 times the mass of the sun, the other 29 times the mass of the sun. They merged together to form one big black hole. I put you on the spot and ask you to add 36 and 29 but I'll do it for you. It's 65, okay? What was discovered was the black hole in the end was 62 times the mass of the sun. Where did the other three times go to? It went into energy. It went into gravitational waves. Three times the mass of the sun went into gravitational waves. Our sun is going to last 10 billion years by burning the equivalent of 10 billion thermonuclear explosions. In one second three times the mass of the sun as these black holes came together got emitted gravitational waves meaning more was emitted in that second than was emitted by all the rest of the stars in the entire observable universe during that one second. It's an amazing event.

Ted Simons: Again, that was 1.3 some odd billion years ago.

Lawrence Krauss: Yes. We just happened to be lucky enough to turn on --

Ted Simons: It makes a ripple at the time.

Lawrence Krauss: Huge ripple. A storm. It's like what a tsunami is like but very far away. It makes this incredible storm in space and time. I think we have another video -- the warping of space and time.

Ted Simons: The last one. Yes. Explain exactly what we're looking at here.

Lawrence Krauss: Here what we have done is we have taken the three dimensions of space and made them two dimension so you can look at the curvature. As those black holes are going around in faraway space looks normal. Nearby, time is slowing down. In the green areas a little bit. In the yellow areas, by 20 to 30%. Those red areas time is being distorted as space is by an amazing amount. It's like the movie Interstellar. Time is almost standing still. One second might be ten years.

Ted Simons: You saw the ripples.

Lawrence Krauss: The ripples are admitted. Those ripples in space, very intense at the source, spread out and over 1 billion light-years when they get here they produce little ripples here on earth, so small that you would never imagine would you detect them.

Ted Simons: But they were. It was like a little ping.

Lawrence Krauss: Because it's a pulse. The merger of those incredibly massive black holes too about a second so the pulse of those gravitational waves produced a one-second pulse that sounds like a ping. When the gravitational waves combine they cause room to go in and out, in that direction and that direction at some frequency. Basically the frequency of the black holes which happens to be the audible range so they are going around each other almost at the speed of light. So it's almost in the audible range. That pulse when it comes by causes vibration. You could say that is almost audible but it's so small you could never actually hear it. We have to build a device that can see that vibration and that's where the amazement really happens.

Ted Simons: We have a video for that, don't we, how this was actually discovered.

Lawrence Krauss: Let me just prepare people for it. I'll show people how it's done, but I want to say what's required. We have two arms of a detector, each four kilometers long. When a gravitational wave comes by one arm gets shorter, the other gets longer. Like that. So you have to measure the difference in length between two arms that are four kilometers long but what's amazing is when that gravitational wave came by it changed the length of one arm compared to the other by the amount of 1/1,000 the size of a single proton. You have to measure them with an accuracy of 1/1,000 the size of appear single proton which is measuring the distance between here and the nearest star to the accuracy of the width of a human hair.

Ted Simons: How do we know it's not some American in Glendale shamming their door?

Lawrence Krauss: Good question. Very good question. The answer is we have two detectors. One in Washington and one in Louisiana. So in fact if a truck hits a pothole 20 miles from the one in Washington, it will produce a large signal. But what they saw was the exact same signal on located that far actually 10 milliseconds apart, which is the time it takes light or gravitational waves to travel between the two. Moreover, they look just like the signal that we predicted by using supercomputers to imagine. It all comes together. It's a golden event so unambiguously clear because of that coincidence and because of the shape of the signal that we know -- we can use that information to determine that's how we know the black holes were 36 and 29 times the mass of the sun. All from relativity. It allows us to apply general relativity and see it works. When you saw those black holes merging together space looked like a storm. We have never measured general relativity where space is doing more than rippling very lightly. I don't know if you want to go through --

Ted Simons: Watch a little bit of it. It's really neat to look at.

Lawrence Krauss: Let's look -- the way you can measure the difference across the two tunnels by sending the light beam back and forth and compare that to the distances. We send a light wave out, split it up. That wave goes all the way to one mirror at the ends of one tunnel and bounces back. If those two tunnels are exactly the same length and those two light beams interfere in such a way so that the screens are perfectly black, but when one screen gets a little bit smaller than the other the light waves interfere in a slightly different way and produce a light image on the screen. So we're basically comparing the two light waves and looking for a mismatch in the peaks and troughs and that signal that you can see now basically signal flashing back and forth. The frequency which it flashes back and forth tells us the rate at which they are rotating and colliding.

Ted Simons: Was this the first direct evidence of black holes?

Lawrence Krauss: In a sense it was because really we have seen objects moving around, objects we can't see. We have inferred there might be black holes, but to emit all of your energy in gravitational waves really only happens through plaque holes. If we had two objects like the sun colliding, a lot of the energy would go out in particles or cosmic rays but with black holes there's nothing but space. So this is in some sense the first evidence not just of plaque holes but the fact that you are have black holes of 30 times the mass of the sun that they form in galaxies, collide in less than 13.8 billion years. That's really important, because there are black holes in the center of every galaxy. We don't know whether they got there first or the galaxies got there first. To figure out how galaxies evolved we have to figure out how black holes evolve. Now we have evidence that these--stars, and by the way, to form a black hole 30 times the mass of the sun you probably had to have an in addition star 100 times the mass of the sun. Now we know those stars form and they form black holes. We're going to learn an incredible amount about astronomy and astrophysics. This is not just a great discovery; it is going to be astronomy of the 21st century. Not just this one which is four kilometers long we're talking about building detectors in space that are 1 million miles long. Mirrors in between two satellites.

Ted Simons: Stephen Hawking said this had the potential to revolutionize astronomy. Explain again why the idea of gravitation --

Lawrence Krauss: This allows us to see where we could never see before. It allows us to see in the dark if you wish. Waves are emitted from near the event, a place we could never see otherwise, this will allow us to explore phenomena in nature that we could never see otherwise, most exotic things like Neutron stars or collision of black holes. With light you could never get into that far and that close but we can look at the Dilation of space and time. Measure general relativity but measure in some sense the properties of colliding black holes which are essential part of the development of the structure in the universe. When we look at telescopes, the first telescope when Galileo turned it on he saw the moons of Jupiter for the first time, he saw them orbiting Jupiter. Not everything orbits the Earth. The Catholic Church didn't like it at the time. Every time we have opened a new window on the universe in the past we have been surprised. When we turn on radio telescope we discovered the afterglow of the Big Bang. This is -- what's amazing, this detector is being built and upgraded over 50 years by numbers of great people who first proposed it in the 1960s, then built it, then other people who made it happen like Kip Thorn and Ray Weiss and Barry Barish and other people. But the event was seen within the first hour of turning on the detector. In fact they were just tuning up the detector. It was called an engineering run. They turned it on and within the first few hours they saw a signal. The rumor I heard five months ago that I found so amazing within the first few hours, they saw a signal that was so clear it rang clear like a bell. You can go to the site and listen to the vibration.

Ted Simons: It's a ping.

Lawrence Krauss: A ping.

Ted Simons: So this is bigger than the Higgs.

Lawrence Krauss: I don't like to claim one thing or another. This is -- they are both huge. They are just huge in different ways. The Higgs is an amazing discovery. In some sense this is more romantic. But these two things represent monumental discoveries that are going to push the forefront of knowledge about the universe. I don't like to rate one versus the other. I think this is something perhaps -- for the Higgs we have been waiting 50 years. For gravitation waves we have been waiting 100 years.

Ted Simons: With that in mind, now, we get this amazing discovery, what is next? What will be thought of, attempted to be discovered?

Lawrence Krauss: Well, that's why I believed the rumor when I first heard it. LIGO has been running more than a decade but it didn't have the sensitivity to detect the events we just saw. It had been upgraded specifically to look for those events. We estimated, how many black holes collide in the universe? We did rough estimates. We said every few weeks or a month or two. But this is just the beginning. They are going to improve the sensitivity so there may be events every day even though they are incredibly rare, once every billion years per galaxy there are 100 billion galaxies in the observable universe. It's just the first of the gravitational wave detectors. There's a whole bunch of them coming online on earth. The next phase is to build them in space. In space you don't have to have a tunnel. Just put a mirror here, float another mirror a million miles away and we can detect very different frequencies and eventually maybe detect waves from the Big Bang themselves. If we detect those that will tell us about the Big Bang.

Ted Simons: Less than a minute left. Make you proud of science? Proud of American science?

Lawrence Krauss: I don't think in terms of American. It makes me proud in terms of the human species. What it is a testament to the fact that the ingenuity and persistence of humans and the fact that we can come together to do this. There are a thousand scientists on LIGO. A few will get credit with the Nobel Prize but we can work together for 100 years to push the limits of the human mind and human technology to discover where we came from and where we're going and I find that the most beautiful thing in the world.

Ted Simons: Good to have you here to explain all of this.

Lawrence Krauss: I'm excited.

Ted Simons: I can tell. Thursday we'll talk to NPR talk show host Diane Rehm about her career and her new book, which focuses on the death of her husband of 54 years and her struggle to build her life without him. That is it for now. I'm Ted Simons. Thank you so much for joining us. You have a great evening.

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