Emperor Has No Clothes award – Seeking the unseen: Gravitational waves – By Lawrence Krauss

Here is an edited version of the speech given by Lawrence Krauss at FFRF’s 39th convention in Pittsburgh on Oct. 8, 2016. He was introduced by FFRF Co-President Dan Barker:
The Freedom From Religion Foundation’s “Emperor Has No Clothes” award is given to public figures who make known their dissent from religion. Lawrence Krauss is an internationally known theoretical physicist whose studies include the early universe, the nature of dark matter, general relativity and neutrino astrophysics.

He grew up in Toronto and received his undergrad in both mathematics and physics at Carleton. He has a Ph.D. in physics from MIT. He joined the Harvard Society of Fellows on the Yale faculty as an assistant and associate professor. In 1993, he was named professor of physics, professor of astronomy and chair of the Department of Physics at Case Western Reserve University. In 2008, Krauss became the foundation professor in the School of Earth and Space Exploration, and is the inaugural director of the Origins Project at Arizona State University. Lawrence is author of more than 300 scientific publications and more than a dozen books, including A Universe from Nothing: Why There is Something Rather than Nothing, and The Physics of Star Trek. His upcoming book will be called The Greatest Story Ever Told.

He also wrote an article last year in the New Yorker on how the U.S. needs an atheist Supreme Court justice.

By Lawrence Krauss

Thank you very much. This is truly an amazing organization and award. I feel very privileged to be here and to be speaking to you.

What I want to do today is talk a little bit about how science treats problems that seem like they’re not solvable or seem like they might be almost metaphysical or religious. We get embroiled in the petty problems of the world around us, and one of the great things about the field that I work in is that it points out that those problems are really irrelevant.

This is a recent Hubble Space Telescope deep field picture (see photo). Every spot in that picture, every dot that you can see, is a galaxy, not a star. There are over 100 billion galaxies in the observable universe, and those small, faint, blue galaxies are about 8 billion or 9 billion light years away. That means that the light from those objects took that long to get to us.

That means that the light came from before the Earth and sun formed because the Earth and sun are about 4.5 billion years old. Since the lifetime of a main sequence star, like our sun, is about 10 billion years, and a lot of those galaxies are 9 billion years old, or the picture is 9 billion years old, so now it’s 9 billion years later. That means many of the stars in this image are no longer around. They burned out. And any civilizations around those stars have burned out. Any civilizations that had awful presidential candidates have burned out. They’re gone. No one’s going to ever know about them and their history.

And similarly, if the light from our sun is eventually captured by another civilization that might go around a new star and one of those systems, it may see us. But they’ll see us 10 billion years from now, and by then our sun will be gone and our civilization will be gone and no one will care. It’s over. And that’s just the way it is.

Uniform universe

When you look at this image, you may ask which direction in the universe is it? And the answer is, it doesn’t really matter, because every direction in the universe looks identical. There is the same number of galaxies out there as out here. Anywhere you look, there is the same number.

But that’s a real problem, a metaphysical problem, which led to much of the research in physics that I am now involved in. We think we have a solution to it, but to understand that, we have to think about the origins of the universe. We want to look back to the beginning of time.

It turns out we can’t look back to the beginning of time using light. If we do, we can only go back as far as the cosmic microwave background radiation, when the universe was about 300,000 years old. It represents a wall in the universe, essentially. If I try and look outside this room, I can’t look outside the wall because it’s opaque. Well, if we look back in the early universe, the universe was hotter and hotter and hotter, and at a certain point it was so hot that neutral matter couldn’t exist. And electrons are stripped away from protons and formed plasma. And that material is opaque.

So if we try and look back to the beginning of time, we can’t, because between us and the beginning of time, the universe was opaque. We can only look back to the moment the universe became transparent. Just like I can look back at all the way to that wall over there because the air is transparent.

This is a baby picture of the universe (see photo next page). A neonatal picture of the universe, when it was about 300,000 years old. And color here represents temperature. So there are hot spots and cold spots. And this is before galaxies, before stars formed, and it looks like the universe has a lot of lumps, and it does. The average temperature of this radiation coming at us today is about 3 degrees above absolute zero. It was 3,000 degrees when it left that surface, but the universe has expanded by a factor of 1,000 in that time, and it’s cooled and it’s now 3 degrees. And it turns out the difference between the hot spots and the cold spots here is 1/100,000 of a degree. So, this is actually incredibly smooth.

And that exacerbates the problem I told you about earlier. The galaxies may look the same everywhere, but why is the temperature of the universe the same absolutely everywhere? And where did the lumps come from?

These lumps are important because they’re going to collapse to form all the stars and galaxies and everything you see in the visible universe. Well, it turns out, we think we understand that. The same thing solves both problems of why the universe is the same temperature everywhere and why there are lumps. And it’s really kind of amazing: quantum mechanics. We think quantum mechanical processes in the early universe produced all the lumps I’m seeing in this room. All the lumps we see in the universe. In fact, the universe is an example of macroscopic quantum mechanics.

Looking back

If we want to try and understand where all this comes from, we’ve got to look back through that plasma. If I want to look through that wall, I might want to use X-rays, because then I could see through the wall. I’ve got to find something that will, in this case, not interact strongly with all that material so it can come from the Big Bang all the way through that plasma and get all the way to our eyes today. Well, we have to think of something that interacts much more weakly than light because light can’t make it through. So what’s the weakest thing in the universe? Gravity.

Some of you may not feel that gravity is weak, but that’s because the entire Earth is attracting every atom in your body. But the gravitational force between each of your atoms and every atom in the Earth is so small you’d never be able to measure it. So, gravity is much weaker than electromagnetism. Now, about 200 years ago, James Clerk Maxwell showed us that if I shake an electric charge, I produce an electromagnetic wave.

Einstein in 1916 demonstrated that gravity was really an effect of the curvature of space. That space itself responds to the presence of matter and energy by curving, by expanding, by contracting. And, therefore, each of you is curving space around you, but not by any amount you can see, because gravity is so weak. But every time I do this [waves his arms around], and I do this a lot, I’m creating a disturbance that produces a ripple in space that travels out at the speed of light. Not an electromagnetic wave, but a gravitational wave. Every time I’m doing this [waves arms], I’m producing a gravitational wave.

Scientists decided that we should try and detect these. So we built the largest gravitational wave detector in the world. There are two of them actually. One is in Hanford, Wash., and there’s an identical set-up in Livingston, La. Each detector has two perpendicular arms, each four kilometers long, and they’re identical.

Long-awaited signal

Now, this detector was built in the 1990s and 2000s, but it didn’t have quite the sensitivity we thought you’d need. It could only detect a change in length equal to one-hundredth the size of a proton. So it got upgraded. In 2015 it achieved the sensitivity of one-thousandth the size of a proton. They were going to turn it on and do an engineering run, which is what you do with big, new machines. Ray Weiss, who was the director of this, said, “Don’t take any data, because we’re just doing an engineering run.” But, of course, they didn’t listen to him and they turned it on. One hour later, they got a signal that we’ve been waiting for since Einstein.

And, in fact, it was a signal that came from an event that happened 1.3 billion years ago. Here is a gold-plated event of a gravitational wave. This discovery could not have been made before last year because we didn’t have the technology — the quantum technology, the optical technology — to build devices that were sensitive enough to this. That’s the first part.

But the second part is, when you see something like this, it only means something if you can compare it to something you can predict. Because if you can’t predict it in science, it’s no good. Science is not a story like religion. It makes predictions. In order to be able to make that prediction, it meant we had to be able to calculate what would happen when two massive black holes collided, and that is incredibly complex because the gravity is very strong. We never witnessed gravity that strong before.

So everything came together. The earliest we could have detected these gravitational waves was Sept. 14, 2015. And that’s exactly when we saw it.

What they discovered, by doing this amazing technology that no science fiction writer would ever suggest you could do, is an event that is equally interesting.

[Showing simulation on screen] These are two black holes 1.3 billion light years away. What’s amazing is these black holes are orbiting each other 200 times a second. Not once a year, like the Earth orbits the sun, but 200 times a second. And in a final hurrah, they will collide. What you get is a massive gravitational wave emission.

In two-tenths of a second, that system emitted three times the mass of our sun in gravitational waves, which means that it emitted more energy in gravitational waves than all the rest of the stars in the visible universe are emitting right now. That’s amazing. You couldn’t make this stuff up.

New astronomy field

The real universe is just so much more interesting than the universe of myth and superstition. And we’ve discovered that this actually happens. This means we’re living in a time that is very similar to the time when Galileo first took his telescope and looked up at the moons of Jupiter. He created a whole new field of astronomy. And this will be a new field of astronomy.

Gravitational wave astronomy will open up a new window on the universe and, if history is any guide, every time we open a new window on the universe, we’re surprised.
But what about gravitational waves from the beginning of the universe? How can we look for them? There is a device that’s been built to look for those called the BICEP detector at the South Pole. This detector looks for the cosmic microwave background radiation, which only comes from the universe that’s 200,000 years old. But it’s looking for an imprint in there that comes from the beginning of time.

This detector was designed to look for a signal from the Big Bang. It’s actually designed to look for a signal from a moment after the Big Bang. But it is a phenomenon that we think happened when the universe was a millionth of a billionth of a billionth of a billionth of a second old.

We think at that very early moment, our universe expanded incredibly rapidly, increasing in volume by a factor of 10 to the 90th in a millionth of a billionth of a billionth of a billionth of a second. It went from the size of a single atom to the size of a basketball. And that was because it was an incredible amount of energy stored in empty space.

Now, one of the reasons we think that happened, besides the fact that our particle physics ideas suggest it might, is it also solves that problem of why the universe looks the same in all directions.

Universal inflation

So we needed to look for something else that would be unambiguous evidence that inflation happened. When you puff up a universe by a factor of 10 to the 90th, that’s going to generate gravitational waves. And the unambiguous prediction is that enduring inflation gravitational waves of all frequencies are generated and we can look for them.

The cosmic microwave background is caused because you’ve got free electrons that are about to be captured by hydrogen and before that, just before their capture, they scatter light to your eyes. Now, if the universe is uniform all around them, the same temperature all around them, they scatter light in the same intensity in all directions. But if a gravitational wave comes by, its size is the size of the visible universe at that time. It causes the universe to get a little smaller in one direction and a little bigger in the other direction. And that means the electron will see radiation that’s a little more intense in one direction and less intense in the other direction. And when it scatters that radiation, it’ll be polarized. That means it’ll be more intense in one direction than another.

Four years ago, the BICEP detector was looking for that polarization, the kind of signal we would expect to see if inflation happened. (A signal that I’m happy to say I had predicted about 20 years earlier.) But it produces a kind of snake-like polarization pattern. In February of 2013, they produced this image. And it shook the world because if this were true, this would be perhaps the most important image in the history of science because it would be the first detection of gravitational waves. This would be a signal from the very beginning of time.

These would be gravitational waves generated when the universe was a millionth of a billionth of a billionth of a billionth of a second old and they’d allow us to test our ideas about the origin of the universe. You notice I said, “If it’s true,” because we just don’t know. It turns out this is called a multiple expansion, but there is the data and there is the prediction from inflation you see. It looks great.

Extraordinary evidence

The reason I wanted to present this to you today is because it’s the difference between science and religion. There were two groups of people looking for the same thing. It was the Holy Grail, if you’ll forgive me, of cosmology. And these guys wanted those guys to be wrong and those guys wanted these guys to be wrong. So what did they do? Did they cut each other’s heads off? No. They said, “Let’s do a joint analysis.”

They didn’t care who was right, they just wanted to know what was right. They knew that one of them was wrong, or maybe they were both wrong. But all they wanted to find out was what the answer was. And to me, therefore, even though many people say, “Oh, it’s unfortunate that maybe this experiment was wrong,” it’s one of the great examples of the history of science because it shows how science works. They got together and they came up with a joint analysis.

And so, if you actually look at their joint paper, everyone says it implies that gravitational waves haven’t been seen. There’s an 8 percent chance that they’re not there. And for physicists, that means there’s no evidence that they’re there.

If you’re going to make an extraordinary claim, as Carl Sagan said, you’ve got to have extraordinary evidence. And 92 percent just doesn’t cut it. You need 99.9995 percent confidence before we can say we made a discovery. That’s what we needed before we claimed we discovered the Higgs boson.

The thing about science that’s really important is that we try to prove ourselves wrong as much as we try to prove ourselves right. And only after we’ve convinced ourselves, after trying to prove ourselves wrong, do we claim we’re right.

But I want to close by asking what would we learn if that was really there? Because we don’t know. We’re doing new experiments to see if it’s really there. New experiments with greater sensitivity. If it’s real, we have seen a signal from the beginning of time.

No supernatural events

I wrote a book called A Universe from Nothing a bunch of years ago, which tried to take back thesequestions from religion, such as “Why is there something rather than nothing?” Well, you don’t need supernatural shenanigans to get something from nothing. But at the time, I wrote about the possibility that most of us think is true right now among physicists — that there is probably more than one universe, or probably many, many universes, out there. Something we call a multiverse.

What happens is there’s a local place where that exponential expansion stops. And when that happens, all the energy and empty space gets converted into particles and radiation in a big bang. So our universe originated when inflation ended at that point. But in other places in this multiverse, inflation is still going on and there may be today a universe just forming and it goes on in most of these models forever. It’s eternal. And the really strange thing is, it turns out that the way inflation ends in each universe can produce different laws of physics in each universe.

That may explain the properties of our universe because it may be, as it turns out, in some universes there may be a lot of galaxies and in some universes there may not be many because the conditions aren’t right. And it could just be that the properties of our universe are what they are because if you didn’t have galaxies, you wouldn’t have stars, if you didn’t have stars, you wouldn’t have planets, if you didn’t have planets, you wouldn’t have astronomers.

So the universe is the way it is because there are astronomers here to measure it. Which sounds religious, but it’s not. It’s just cosmic natural selection. You would not expect to find yourself in a universe in which you couldn’t live. But the neat thing is this speculation may now be testable. Not directly, because we’ll never know those other universes exist, but if we could measure gravitational waves from inflation and demonstrate that inflation happened, and measure the properties of inflation, we’d be able to know if inflation is eternal. And if that’s the case, we would know that there are other universes out there.

In this case you could have a theory, a grand unified theory, that would explain everything we can see about the universe in which we live. And so I’m amazed that we are potentially on the threshold of knowing whether we are alone in a cosmic sense. Whether there are other universes, or whether our universe is unique. And, of course, if there are a multitude of universes then that makes, of course, God even more redundant.

So, let me close by going back to this picture from the beginning of my talk. When I look at a picture like this, I think about the civilizations that may have died there on these planets that may have been around these stars. I think about why the universe is the way it is, and it caused us to do the work we’ve done over the last 40 years. This is spiritual. This is all. But this beats the spirituality of religion because it’s real.

Freedom From Religion Foundation