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Evidence of cosmic inflation expands understanding of universe’s origins

March 18, 2014 at 6:23 PM EDT
Scientists say they have found evidence confirming a theory that our cosmos expanded from almost nothing to its first huge growth spurt in just fractions of a second after the Big Bang. A telescope at the South Pole revealed patterns and skewed light waves created by gravitational ripples from the incredible expansion. Gwen Ifill interviews Sean Carroll of the California Institute of Technology.

GWEN IFILL: It’s a mind-boggling concept: Our cosmos expanded from almost nothing to its first huge growth spurt in just a trillionth of a trillionth of a trillionth of a second. And that was after the Big Bang.

Scientists said they confirmed that theory by using this telescope at the South Pole to look at the oldest light detectable. The light reveals patterns and skewed light waves, shown here in red and blue, that were created by gravitational ripples during the — this incredible expansion known as cosmic inflation.

Sean Carroll is a physicist, cosmologist and author at the California Institute of Technology, and he joins us now to explain all of this.

And we need your explanation. Start by explaining cosmic inflation. What a term.

SEAN CARROLL, California Institute of Technology: Well, it is.

The term cosmic inflation was coined around 1980, when the ordinary economic inflation was also very much in the news. And it was Alan Guth, who was a young physicist at the time, who came up with the idea that we need to explain certain very basic features of the universe.

For example, it looks similar, it looks smooth all over the place. And so, if in the very earliest moments, the universe went through some enormously fast, super-accelerated expansion, it’s like pulling at the edges of a sheet, and that expansion would actually smooth things out.

GWEN IFILL: How does this compare to the — was it 1998 that — the discovery of dark energy? How does this compare to that?

SEAN CARROLL: Well, it’s very similar.

In both cases, we knew that this was a possibility. In both cases, we were a little bit surprised that it came along the way it did. Dark energy was a — was a game-changer in terms of our understanding of the current look at — of the universe, what it’s made of and so forth.

And we have been trying to understand the very earliest moments. Before yesterday, the earliest moment in the history of the universe, about which we had data, was one second after the Big Bang. And now, like you said, it’s a trillionth of trillionth of trillionth of a second after the Big Bang.

GWEN IFILL: So, when we think of the universe, we think of something expansive and endless and almost unmeasurable. And you’re saying that what we know about the universe so far is just a speck of that, of what it really is?

SEAN CARROLL: Well, certainly, we only see a certain finite amount of universe. It’s still very big.

We see a part of the universe that has hundreds of billions of galaxies in it. And the amazing thing about the Big Bang model is that, in the far past, 14 billion years ago, all of this stuff was squeezed down to an incredibly tiny distance.

And so what physicists have done is to take the laws of physics, as they understand them, to extrapolate them well beyond anything we had ever seen before, made a prediction, and that prediction came out to be correct. So, we really have a much better idea now than we did a couple of days ago that we’re on the right track when it comes to what was happening right after the Big Bang.

GWEN IFILL: Now, those predictions have always been theories. How do then you go about proving a theory not to be a theory, and is that what we have actually done here? Has it been proven?

SEAN CARROLL: Well, you know, science in some sense never proves anything.

It’s all about gathering evidence, reaching conclusions, because the overwhelming amount of evidence goes for one model, rather than some other model. So, at inflation, you have a well-defined theory of what could have happened right after Big Bang. There are competitors to inflation, but none of them were really quite as well put together as inflation ever was.

And inflation made this very specific prediction that the competitors didn’t really make. So, right now, inflation is way above everything else we know when it comes to understanding the early universe. That’s not to say that, tomorrow, some brilliant young scientists is not going to come up with an even better model.

GWEN IFILL: Why was this experiment done at the South Pole? What is it about the South Pole that lends itself to explorations of space?

SEAN CARROLL: You know, the South Pole is a little bit different than you would think. It’s obviously very cold, like you would think, but it doesn’t snow at the South Pole.

The air is actually very, very dry, and it’s at a very, very high elevation. There’s snow on the ground. And it drifts around a lot, but when you look up into the sky from there, you see the universe very, very clearly. So, even though it’s a tremendous pain to get down there, and once you’re down there, if you’re down there for the winter, you’re not coming back until the winter is over, but it’s a great place to do observational astronomy.

GWEN IFILL: Now, for those of us who think this stuff is really cool, it is very cool, but what is the practical impact for most people when we talk about — when we trumpet such exciting discoveries?

SEAN CARROLL: There is absolutely zero practical impact in the conventional sense.


SEAN CARROLL: Understanding the origin of the universe is not going to cure any disease. It’s not going to build you a better smartphone or anything like that.

What it will do is help us as a species understand our place in the cosmos. So, I personally think that that should affect your everyday life. It helps us really appreciate what the universe is, how it behaves. And that has to feed into how we think about ourselves.

GWEN IFILL: So, it informs the way we see our world and our place in the world, in the larger universe?

SEAN CARROLL: Yes, what separates us from merely existing, surviving from day to day is that we are curious. We are creatures that want to understand.

Like Carl Sagan, whose “Cosmos” is back on TV now with Neil deGrasse Tyson, Carl Sagan once said, we are the universe’s way of thinking about itself. We are a collection of atoms and particles, just like the rest of the universe, but we have the power to theorize, to go out there and collect data, and to understand the context, this wonderful universe that we live in.

GWEN IFILL: It sounds almost theological.

SEAN CARROLL: Well, I think it’s a very similar impulse that drives people to theology and to science. You want to understand the bigger picture.

I think that science is different than theology in many ways, one of which is, you have got to make predictions, and if the predictions don’t come true, we throw away your theory. So, the wonderful thing now is that this extrapolation from Alan Guth and collaborators over 30 years ago, somehow, miraculously seemed to get the right answer, and our ability to comprehend our cosmos has been demonstrated once again.

GWEN IFILL: But it still requires corroboration.

SEAN CARROLL: Oh, absolutely.

You know, this is a result of the specific telescope called the BICEP2 Collaboration. And they’re very, very good. I know a lot of scientists who are on this experiment. And they’re super careful and they try their best. But we’re not going to absolutely believe it until someone else sees exactly the same thing.

The good news is that there’s half-a-dozen experiments that will be checking this result. So, in a year or two, we will know absolutely sure whether or not this is real.

GWEN IFILL: Sean Carroll at Caltech and author of “The Particle at the End of the Universe,” thank you so much.

SEAN CARROLL: My pleasure. Thanks.