Horizon, Host: Ted Simons

March 17, 2014


Host: Ted Simons

Krauss on Science


  • Arizona State University physicist Lawrence Krauss joins us for his monthly update on the latest science news.
Guests:
  • Lawrence Krauss - Physicist, Arizona State University
Category: Science   |   Keywords: science, krauss, physicist, asu, news,

View Transcript
Ted Simons: Good evening, and welcome to "Arizona Horizon." I'm Ted Simons. World famous physicist Lawrence Krauss stops by the "Arizona Horizon" set every month for an update on the lightest science news. Tonight, big news on what may have happened immediately after the big bang. Here now to explain is Lawrence Krauss. You know, sometimes I can be accused of being a little hyperbolic, big news, this is huge news.

Lawrence Krauss: You can't be too hyperbolic about this. This could be one of the greatest scientific discoveries ever. And now I was thinking, you're going to talk about taxes later, nothing is certain but death and taxes. Now it looks like even more than ever the big bang was certain.

Ted Simons: We're talking about gravitational waves, we're talking about primordial gravitation -- What are we talking about?

Lawrence Krauss: What we're -- What was just announced today at a news conference, a press conference and also a conference for scientists was a discovery of a signal from the big bang. A new window back to the beginning of time. And we'll have time to work through this. What the signal was were these things called gravitational waves. These waves we have every reason to believe for reasons we'll go into, they were generated when the universe was less an millionth of a trillionth of a trillionth of a second old. And it will allow us not just to directly observe almost the beginning of the universe, turning medium physics into physics, but explore the properties of the physical universe on energy scales that are 10,000 billion times bigger than the scale of a large hadron collider. So it's an unbelievably massive result. It makes our understanding of the universe empirical back to a time that's orders and orders of magnitude before we were earlier able to see. If we look out, we've talked about this before, when we look out at the universe with light, we can only see as far as the light can come from. I can't see past the walls of this studio. In the early universe, the universe was hot and opaque, and light couldn't get through the plasma particles. When the universe was about 300,000 years old, matter became neutral and the universe became transparent. So when we look out, we can see that surface if you wish, where the universe first became transparent. Radiation coming at from us all directions from that surface, which was originally 300,000 degrees, but it's cooled now to three degrees. So up to this point when we want to look back directly at the big bang, the farthest we can see was back to a time 300,000 years after the big bang. But gravity waves, and we'll talk about them, are so weakly interacting, gravity waves can make it all the way back to us. So we'll get an image of the universe when it was a millionth of a trillionth of a trillionth of a second old.

Ted Simons: You're talking about echos I guess of the big bang. So how do we know that these gravitational waves existed or started at that time period?

Lawrence Krauss: One of the reasons is the strength of gravitational waves depends upon the energy. I'm creating gravitational waves right now when I wave my hands. Einstein said something remarkable. Just like when I shake an electron back and forth I create electromagnetic waves which allow the signals to be broadcast so viewers can watch them. Whenever you move a mass up and down, you create literally ripples in space and time. Gravitational waves, which are ripples in space when a gravitational wave comes through this room, it changes the distance across the room by a very small amount, and in fact it compresses and stretches us in one direction or another. But they're so weak, we can't detect them. We've built them here on earth, the biggest ones are the LYGO detector, there's one in Washington state and one in Louisiana. And it's amazing what they can do, but they still haven't seen gravitational waves. There are detectors that have two tunnels, each two miles across, and when a gravitational waves comes by, it may change the length of one tunnel a little bit compared to the other. And they've designed things so you can measure the change in a two-mile-long tunnel to an accuracy of better than the size of a proton. A single proton. It's unbelievable. But they still haven't seen gravitational waves because even if you bang neutron stars far away, the signal is so small. In order to create a signal that is big enough to see, you need incredible amounts of energy. And that energy if you wish, only existed in the very early universe when the universe was so hot, and the temperature was so high, that violent things could happen.

Ted Simons: Basically, because another question for me would be, OK, you see gravitational waves, you found these things, whoop-de-do. How come it's not a couple of universe or plants colliding one billion years or 500,000 -- How do you know this --

Lawrence Krauss: First of all, we know because we'll talk about how it was discovered in a bit, because it distorts the background radiation, it basically had to have been around before there were stars and planets because the mike wave background was created well before stars, planets or galaxies existed. So it has to be primordial. It's distorted the light coming to us from that background surface. Also the scale of it, the size of these -- The distortions are immense. So big, the wavelength of these things exceeds the size of -- It's almost the size of the visible universe. And so there's no way that colliding black holes, or you or I run nothing each other fast can create waves like that. No only -- Not only will the intensity be smaller but the sides will be smaller. Everything about these smacks of the early universe. But more interestingly perhaps, our best picture of the early universe, inflation, which says that at very early times the universe expanded very rapidly due to an energy stored in empty space, if you wish, and that energy decayed and produced all the galaxy and stars we now see. Something from nothing, which as you know is something I like to talk about. That -- What is equally remarkable, we can make a prediction, that theory explains the nature of the cause in mike wave background, everything we see about the universe. But we really needed a signal of that theory, inflation, and many people, including myself, have predicted years and years ago that if inflation happened at a high enough scale, the gravitational wave background intense enough would it affect the image seen from the mike wave background. I don't think any of us thought it would be that strong. What's amazing is the signal that's been seen is so strong, that it suggests this inflation happened at a scale called the grand unification scale, which is a scale we would have guessed. When we look at the forces of nature, we have hypothesized that they come together, they all come together to form a single force at a scale that's 16 orders of magnitude smaller than the size after proton. If they do, it will produce a signal they have seen.

Ted Simons: What are we looking at here?

Lawrence Krauss: A bunch of lines.

Ted Simons: It looks like a game.

Lawrence Krauss: It looks like a game. What we're seeing is when the mike wave -- When the gravitational waves come through the microwave background, they'll alternately compress space in one direction and stress it in another. That will cause the radiation to be more intense in one direction than another. We call that polarization. And a gravitational wave that comes through the microwave background will produce a particular pinwheel type pattern of polarization changes just like you see here. Nothing else we know of will produce that pattern. What you're looking at in a sense is the direct image of gravitational waves stretching space in one direction, and compressing them in another. If this is confirmed, this will be the first direct detection of gravitational waves which are predicted by Einstein, well, Einstein's theory developed in 1916.

Ted Simons: Real quickly, have these waves always been there and we're just finding them? Are they going to be there again tomorrow?

Lawrence Krauss: They've been -- They were produced in the early universe, they are permeating the universe today just like the microwave background is, and they'll continue to exist, they'll get weaker as the universe expands, but they have been -- Because of the only things that can permeate that plasma, they're the only things that really could give us a direct signal. In fact it's like having a new light. We can't see what is normal, it's like having x-rays but it's better, because they allow us to go through all of that dense stuff between us and the big bang, and see right back to the beginning.

Ted Simons: It's like a curtain between us and the big bang.

Lawrence Krauss: Exactly. And these things get right through the curtain. That's why I've been so excited in studying these things for much of my career.

Ted Simons: So how do you prove this?

Lawrence Krauss: Well, it's a good question. First of all, the -- You could rule out all other signals, anything else that could produce that kind of signal. Also inflation makes various predictions that says the gravitational waves will have a certain strength, they'll have a certain intensity for different wavelengths which we can try and measure, and you'll also compare their intensity with different wavelengths with the other lumps we see in the microwave background. These are all tests we can do of the fundamental idea. And basically, ultimately we also, very importantly, we have to confirm with this, this is a single observation. Since it could be the most important observation made about the universe in our lifetime, if not in the last century, extraordinary claims require extra evidence. A single claim should never be trusted. But the good news is, there are dozens of experiments including the plank satellite up there which are poised -- You see, it's hard to identifying something -- Find something if you don't know what you're looking for. This happened in 1992, everyone was looking for them but within months of the time the satellite discovered them, everyone else was able to confirm it, because once you know what you're looking for it's easier to find. So there's dozens of experiments in the south pole, in space, that are prime to be able to test this. So we'll know soon if it's true.

Ted Simons: These were found by a telescope at the south pole?

Lawrence Krauss: The south pole is the best place to go next to space, because it's very, very dry, and very, very cold. And it's a really good place to look for mike waives because you're looking for a background that while -- A background of radiation that's only three degrees above absolute zero. You want to shield out any noise from the earth and the heat from the earth, but also water and things in the atmosphere absorb these mike waves, so the south pole is the best place to go. That is unless you're someone who has to do it because you have to spend the winter in the south pole. One of the people on the experiment is a former student of mine who had to winter over in the south pole and that's a difficult thing to do.

Ted Simons: Not a lot of laughs --

Lawrence Krauss: yeah.

Ted Simons: Is this like the holy grail of -- Is this a Nobel prize winner, is this big, big --

Lawrence Krauss: This is the holy grail. The one remaining thing, the smoking gun that would tell us if this idea of inflation was right, was gravitational waves. I've been arguing that for almost 30 years. And so lots of people were looking for it and lots of -- And that's what's surprising. At least one, the plank satellite reported an upper limit. And the upper limit is below the level that these people are seeing. So that's why we have to make certain, well, there are reasons to believe you can make both those results concordant, but it's cause for hesitation at least, because these are not -- These are about as big as they possibly could have been and not been seen up to now. And that's amazing. But they've done a very careful job, because they're not dummies. They've been analyzing this for three years because they knew the whole world woould be watching. This is not only a Nobel prize, but this is a game-changer because it means for those people who like to say, oh, I don't believe in the big bang, no one was around, how do you know it was there, this is someone calling to us from the big bang. Not someone, but something calling to us. This is seeing the big bang. Just like seeing the sun. And there's no -- Once we measure it, there's no denying it, and those people who don't believe it can stick their heads in the sand more, but it's way too late.

Ted Simons: How do we know that these -- Why weren't they -- 14 billion years to get here, shouldn't there have been a bump into something here and there?

Lawrence Krauss: They're so weakly interacting, they basically pass through everything without changing. Gravity is the weakest force in nature. Gravity is incredibly weak. We don't think of that, we've talked about it, we don't think about it because we feel when we try to jump, but that's because the whole earth is interacting. Gravity is 40 orders of magnitude weaker than -- To the waves pass, they're the best messengers from the early universe and the beginning of time, now we have a window in principle, the first window to directly probe that era.

Ted Simons: Textbooks will be rewritten because of this?

Lawrence Krauss: Absolutely. Absolutely. It doesn't change the idea of the big bang, but it makes it empirical. It turns speculation into hard science.

Ted Simons: Provided it can be proven.

Lawrence Krauss: Provided it can be tested. And confirmed. And that's the thing. And what we try to do is continually prove falsified data to see if it's wrong. We look for every possible reason it could be wrong and believe me, scientists are going to do that. The competitors of the experiments will do that. They had this result three years ago, they've been working on it for three years, to try and make sure they didn't make a mistake.

Ted Simons: I'm really glad we had you on the day that this thing broke.

Lawrence Krauss: The timing couldn't have been better. It's a memorable day in the history of science.

Ted Simons: All right. Great to have you here.


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