Exploring An Ever-Expanding Universe

Saul Perlmutter shared the 2011 Nobel Prize in physics for his discovery that the universe was expanding at an accelerating rate. Perlmutter explains how supernovae and other astronomical artifacts are used to measure the expansion rate, and explains what physicists are learning about "dark energy" — the mysterious entity thought to be driving the acceleration.

IRA FLATOW, HOST:

This is SCIENCE FRIDAY, I'm Ira Flatow. Way back in 1998, scientists announced a stunning discovery, a strange force that was pushing the universe apart. Now we knew at that time that the universe was expanding, that after the Big Bang, the stuff that makes up our cosmos was flying apart. But physicists thought the expansion would slow down, that eventually gravity would pull the parts of the cosmos back in.

And what they found instead was a shocker. Not only was the expansion not slowing down, it was speeding up. The universe was expanding at an accelerating rate. And that discovery earned my next guest a slice of the 2011 Nobel Prize in Physics, and he's here now to tell us about the strange dark energy and the rest of the story.

And if you're here in the audience at Stanford now, this is your chance to talk to a Nobel Prize-winner, Saul Perlmutter professor of physics at the University of California, senior scientist at Lawrence Berkeley National Laboratory. Thank you for being with us here today. Good morning.

What was that experience like? What were you trying to find, and were you surprised by what you found?

SAUL PERLMUTTER: Oh, I mean definitely. We were - it was a long project. We had set out what we thought was going to be a really difficult three-year project to figure out whether the universe was slowing down enough that some day it might actually come to a halt and collapse. And I thought that was just going to be a great project.

You could actually do a measurement, you know, just go out and measure the brightness of some stars, and these happen to be exploding stars, and see whether the universe was going to come to an end some day. You know, what could be a better project?

FLATOW: Sure.

PERLMUTTER: Then as we went, you know, after about three years into the project, we had just been able to show how you could find some of these exploding stars, the very first example of the supernova. And then about oh, you know, six years in or five years in, we were able to show how you could do this in a really systematic way and get enough of them to study.

About nine years in we actually had enough, you know, supernova to do something with, and so we, you know, finally, during this ninth year, we were actually looking at the data and realizing that it didn't look like what we were expecting. And...

FLATOW: And so what did it look like? You found this expanding force, it was expanding instead of...

PERLMUTTER: Well, of course we knew it was expanding, right, and we were making the plots to, you know, see what the history was like in the past, whether it was slowing down a lot or slowing down a little. And of course the plots all started looking a little bit strange. They were not slowing down at all. It was actually starting to speed up - or appeared that it had been speeding up in the recent, what, half of the lifetime of the universe.

FLATOW: Right.

PERLMUTTER: So at that point of course you're doing so many steps of the project that your immediate assumption is oh well, you know, we still haven't finished calibrating yet. You know, I'm sure the graph will look, you know, will look fine, you know, next month once we finish, you know, this step and that step and the other step, and everything's calibrated. It'll be, you know, one of the answers that we were looking for to see, you know, what the fate of the universe is.

FLATOW: And it didn't happen?

PERLMUTTER: And it didn't happen. So, you know, months went by. We, you know, started calibrating the - not just the obvious things but the - revisiting the non-obvious things, and little by little, we started getting used to the idea, you know, this is our result. It's doing something very strange.

FLATOW: And you shared the prize with another team who found the same result as you did. Is there a rivalry there?

PERLMUTTER: Oh yes, the two groups were, you know, racing each other, you know, in these last years, the last, you know, four years or so of this project. And now, you know, it should be said that even in the toughest rivalry, you're basically sympathetic to each other in some ways because you're both having the same very difficult experience of trying to, you know, manage with the bad - with the ups and downs of the weather.

And so there were sometimes where even though we were, you know, fierce rivals, we would cover for each other, and we, you know, we'd observe some things that they needed, or they traded a night with us to cover when we got a bad-weather night.

FLATOW: You mean observing at the telescope?

PERLMUTTER: Oh yes, sorry, right. But still we were - you know, it was definitely a fiercely fought finish. And so it was very exciting as we all reached that final last few months, and apparently they were having those same, you know, concerns and worries during the same period while we were also looking at our data.

FLATOW: Were the rest of the physicists who were watching this and not involved, where they skeptical about what you came up with, said, come on, this is upsetting everything we know?

PERLMUTTER: Absolutely, no, and I think the very first presentations of it, you know, there were certainly other scientists at the meetings who said, you know, this has to be wrong. I mean, I'm sure something will turn out to be wrong with this result. On the other hand, it's also true that they saw the result coming out of two rival teams essentially at the same time, and they knew that the two teams would be delighted to find what was wrong with the other team's results. And the fact that we were both getting the same gave people pause.

FLATOW: Not only was that - I remember when we covered this on SCIENCE FRIDAY when it came out, and I had Steven Weinberg, another Nobel Prize-winning physicist, on the program. And he actually blew my mind when he said not only is it strange that we have this expanding force, but there should be more of it. There should be a lot, lot more of it.

You know, it's almost like that Woody Allen line about the food, you know, so little portions. There should be so much more of this strange thing. Explain that.

PERLMUTTER: Yeah, no, well, first of all the numbers are absolutely ridiculous. If you asked a theorist to predict, you know, about how much of this energy that could cause the universe to accelerate there should be, you would get numbers that are 10 to the 120 times bigger than what we actually saw.

FLATOW: That's a big number.

PERLMUTTER: It's been said this is the biggest embarrassment in all of theoretical physics.

(LAUGHTER)

PERLMUTTER: But it's already - it was already an embarrassment even before we saw this result. People had just assumed that there was something out there, some part of the theory that we hadn't quite understood that would make the contributions to this energy completely cancel, and that the fact that it was so small meant that really it was zero. That, you know, if you had to cancel it down to one part in 10 to the 120, you must cancel it completely. There must be some symmetry in the universe where you get just as much, you know, positive as you do negative, and it comes out to be zero.

And that's what people had always assumed. But now we were saying something that sounded even more bizarre, that not only do you have to cancel to one part in 120, but you have to leave a little bit leftover at that point. And that, you know, that definitely was a problem.

FLATOW: And then they dragged Einstein into this thing, saying that Einstein had talked about the cosmological constant that had called the biggest mistake in his career. And now you and Einstein's name were linked in the same sentence. How did that feel?

PERLMUTTER: It's certainly fun. I think, you know, the best thing for parents is to have, you know, your child's name in the same newspaper article as Einstein. So...

(LAUGHTER)

FLATOW: So you made your parents happy.

PERLMUTTER: Absolutely.

(LAUGHTER)

FLATOW: And is there any practical use we can make out of knowing...?

(LAUGHTER)

FLATOW: I ask this question because we ask this question a lot, because we talk a lot about basic research.

PERLMUTTER: I mean, it's an interesting question because, you know, on the one hand, I can't imagine anything more impractical than studying the history of the expansion of the universe, because, you know, everything you're trying to figure out has to do with changes that happened over billions of years and changes that will happen over billions of years. And most of us just have a, you know, hard time worrying about something that isn't going to affect us next Saturday.

So in this particular case, though, what's interesting is almost anytime that we've made a big advance in the world, where it's just changed our technology dramatically, and we're - you know, the world seems different because of it, it has to do with something that was a very basic, fundamental research project for somebody that was purely curiosity-driven.

You know, I'm sure there must be exceptions to that. But, you know, a great example of this is Einstein's theory of relativity. I can't, you know, imagine anything that seems more impractical than a theory that has to - that will tell you things about what happens when you move a clock, you know, accelerate it near the speed of light. It just seems irrelevant.

On the other hand, you know, we now have, you know, these gigantic industries all built around the fact that GPS works. And, you know, global positioning satellites, that wouldn't - we wouldn't be able to do that if we didn't have that fundamental deep understanding.

And it happens over and over again in this somewhat magic way. I don't know whether we can predict that it'll always keep happening. And we certainly cannot predict on any single topic. So the fact that dark energy and the accelerating universe today has no practical application, we can't say oh, well that means that we know someday we're going to have a whole technology based on this.

On the other hand, you have to do this kind of curiosity-based research or you never get there.

FLATOW: Yeah, we had Jeffrey Hangst at CERN, who was on a few weeks ago, actually two years apart. He works with antimatter. And he's the one who trapped antimatter in a bottle. And we had a nice, interesting discussion with him, and I asked him the same question at the end, is there any practical, and he - long pause, it was quiet, and he said absolutely nothing.

(LAUGHTER)

FLATOW: And he said that's what we do, you know, basic research, and we're proud to have absolutely nothing that does move along somewhere along the line.

PERLMUTTER: And it's a funny business because, you know, right now you find yourself quite worried about this in a period in which people are looking, you know, where can they save money in budgets. You know, industry is definitely saving money by not doing basic research. Government is tempted to save money by not doing basic research. And it's so hard to see the way in which the only way you get major advances that make a difference in our society seems to be to do something that so impractical as basic research.

FLATOW: But you have to convince people about the need to do the basic research, especially the people who are going to pay for it, right?

PERLMUTTER: Absolutely. Now of course, you know, not only does it have this highly practical and yet difficult-to-explain connection, but there's also this aspect that, you know, why, you know, what does it mean to be, you know, a human being in a world where you don't explore what kind of world we live in.

FLATOW: I'm sure the second question people are going to ask you about is why does it happen, why is it happening, this expansion. What's going on?

PERLMUTTER: And of course that's the - that was the really fun aspect of this particular project, the fact that we set out to answer a seemingly, you know, very important question, you know, the fate of the universe, and yet what we discovered was that not only do we not know the answer, but we've opened up what looks like a whole new part of the puzzle of how the world works that we hadn't even realized existed before.

It could be that 70 percent of the universe is made of this thing that we haven't explored before, and now we're in this whole new era of trying to figure out what it is. When we say - we use the term, oh, you know, the acceleration of the universe is caused by dark energy, I think people sometimes think that means that we know what it is.

But the dark in the word dark energy just means our ignorance. It means that we have no idea what it is, and now we have the fun of trying to figure out what is most of the universe made out of.

FLATOW: Do you ever speculate on what it might be?

PERLMUTTER: Oh, I mean all the time. In fact I was talking the other day, and in terms of the - you know, what is it that the theorists in physics have been doing, it's - there's been a paper published essentially every 24 hours for the past, you know, what has it been now, 13, 14 years, on exactly that question of what could it be.

FLATOW: Wow, well we're going to get into a few of those possibilities. Do you have a pet one that you like?

PERLMUTTER: To be honest, I think the question is still wide open. I think there's a huge variety of things that it could be. I have ones that I think would be fun, if the universe was that way.

FLATOW: Give me one that...

PERLMUTTER: I mean, I particularly enjoy the ones in which we get multiple chances at it, so that the universe, you know, oscillates and expands, and then you get another chance, and it expands again, and then you get another one, and it expands again. Some of these repeated ones to me just sound, I don't know, they sound more fun.

FLATOW: We'll talk more about fun with Saul Perlmutter, at - he is a professor of physics at University of California, Berkeley senior scientist at Lawrence Berkeley National Laboratory. We're going to take a break, talk more about the universe, how it's expanding at an accelerating rate, and we invite you to come up to the mic and ask questions. We'll be right back after this break. Stay with us.

(SOUNDBITE OF MUSIC)

FLATOW: This is SCIENCE FRIDAY. I'm Ira Flatow. We're talking this hour about the universe and how it's expanding at an accelerating rate, among other big ideas in physics that maybe we'll get into now with my guest, Saul Perlmutter. He is a Nobel Laureate in physics, won - shared the Nobel Prize for the discovery of this mysterious dark energy.

Do people confuse the dark energy with the dark matter?

PERLMUTTER: All the time.

FLATOW: Give us a little...

PERLMUTTER: So the dark matter is a problem that we've known about from well before this period. When - it was recognized that galaxies seem to be - you know, it's a group of stars that are held together by gravity, but it seemed to be that there was more holding them together than you could see lit up in the stars.

Now, you know, that's not shocking. Not everything in the world glows in the dark. And so you can imagine that there would be, you know, this matter out there that would be holding the galaxy together. But the more we've tried to understand what that matter might be, the more we've realized that it's probably not just bricks or, you know, small planets or things of that sort.

And so now the hunt is on to try and figure out what that dark matter is that could - that is providing this extra gravity to hold galaxies, and in fact clusters of galaxies, together.

Dark energy, of course, is this new extra term that has to do with what is it that's making the universe speed up in its expansion. What could power this reproduction of space so that you get more and more of it faster and faster?

FLATOW: But add it all up together, and you're saying the only thing that's light, that's not dark, is four percent of the whole universe.

PERLMUTTER: That's right. I mean, the stuff that we see around us, that we're made out of, turns out to be just a small fraction of what is really out there. You know, there's 70 percent of it is this dark energy, and then there's, you know, 20 or whatever left for dark matter.

FLATOW: Let's go to the audience, yes, sir.

DANTE SIMONE: Hi, I was wondering - my name is Dante Simone(ph). I was wondering if you thought that the universe would ever end and stop completely.

PERLMUTTER: Well, there's - it's still completely wide open. We don't know the answer. And there are different ways in which you could imagine a universe coming to an end. The way that we had long thought we would be, you know, facing would be is if there's enough stuff in space that the gravity could slow the expansion to a halt and eventually let it fall back together again.

You could imagine, you know, what begins in a big bang might end in a big crunch. So that was the traditional worry, I guess. But now of course we're in a situation where it doesn't seem to be doing that at all. It seems to be doing the opposite. It seems to be getting - expanding faster and faster. But since we don't know why it's expanding faster, we can't say for sure that that's going to keep going.

For all we know, this is being powered by some field in empty space that will decay away, and then maybe we'll get back to the original scenario I just showed you, and it will still perhaps slow to a halt and end in a crunch. The other question is what counts as an end. I mean, if you end up with a universe where everything is empty and cold, and nothing's happening, that could be thought of as an end, as well. So it's possible we'll end up in that, you know, in that end, you know, also.

FLATOW: To make this story - thank you for the question.

AUDIE SIMONE: Thank you.

FLATOW: To make this story even more mysterious is the fact - now get this - I'm not going to get the details right, that's what I have you here for - is that this force didn't kick in until a certain time, right?

PERLMUTTER: Yes.

FLATOW: The universe was just going along away, and suddenly (unintelligible) like that.

PERLMUTTER: No, in fact, you know, for the first half of the life of the universe, it was being slowed down because we - things were all closer together. In other words, the - in an expanding universe, you know, what's expanding is all the distances between every, you know, object and every other object is getting bigger. And of course gravity gets weaker the further apart things are from each other.

Eventually, everything got far enough apart from each other that gravity was no longer as important as apparently this energy that was waiting, lurking in the background in empty space, and it took over and started to speed up the expansion.

FLATOW: Well, how long ago was that?

PERLMUTTER: It was about halfway back to the beginning of the universe, about seven billion years ago. So for the first seven billion years, we were, you know, coasting along and slowing.

FLATOW: And we were smart people because we knew that was happening, right.

(LAUGHTER)

PERLMUTTER: And of course, you know, it took a little while for us to evolve and you know, build our telescopes and eventually catch these photons of light to figure out the fact that seven billion years ago apparently it stopped slowing and started speeding up. In fact one of things that we're now doing is trying to see if we can track exactly how that happened in very, very fine detail because if we want to explain why this is going on, we need to look at the different predictions of these different theories of dark energy. And they will slightly change the prediction of exactly how you go from the slowing to the speeding up.

FLATOW: Just fascinating, yes ma'am.

FANYA: Hi, my name is Fanya(ph). Way back before Einstein, we had ether to explain how light traveled, and how is dark energy different than ether? Could you say something about the two?

PERLMUTTER: Sure, so the ether, you know, was thought to be the medium, you know, in which electromagnetism and, you know, light was traveling. And of course the early experiments showed that that was, you know, that was not the case. But it was not soon after that we started realizing that empty space, you know, even if it doesn't have what we would traditionally think of as an ether that would have preferential directions where, you know, you could go easier in one direction than another, it - empty space itself is a pretty busy, active place.

And so you constantly have - well first of all you fields in the empty space. You're familiar with, you know, the way magnetic fields, you know, when you move two magnets next to each other. And so you know that there is - there are things in empty space like magnetic fields. But it turns out there are lots of other fields in empty space. So it's already busy that way.

And then particles can appear and disappear in tiny fractions of a second. They sort of - you know, you get a glimpse of a particle and anti-particle, and then they disappear again and combine and disappear. And so the empty space that we - you know, the best you can imagine is sort of this humming soup of particles and fields, all appearing and disappearing.

And that's what we believe is actually responsible for some of this dark energy effect of making the universe expand faster and faster, that the energy associated with that humming, buzzing, you know, empty space itself.

FANYA: Is it directional or uniform?

PERLMUTTER: So far we believe that it does not have a direction associated with it. And so that is something that would change it, that would be a little different from what the original worries about ether were, thoughts about ether were.

FLATOW: Yes, ma'am.

MARY: Hi, my name is Mary(ph). What is the universe expanding into?

PERLMUTTER: Ah.

FLATOW: It's the oldest question, isn't it?

PERLMUTTER: No, no, exactly.

FLATOW: The oldest question.

PERLMUTTER: So I've been thinking for a long time that if we could get away from the term Big Bang, it would really help a lot because the - it makes you immediately think, I mean I think we all do, we immediately start picturing this, you know, explosion. And we have this nice picture, oh, it's a big bang, and we see it all bubbling out.

And then we start finding ourselves thinking OK, but the universe is everything. What's it - you know, how can the universe be exploding into this stuff that's not universe. And that's - I think the way to get around that picture, I've been trying it out, is this. So - and I think this is the way most scientists in the field are probably thinking about it.

If you imagine just today that we live in an infinite universe, we're not sure, but imagine that it's infinite, that means it goes on forever. You know, that direction, you'll see galaxy after galaxy, and, you know, into the wall behind me, there's galaxy after galaxy and up and down, it just goes on and on.

The only thing that you need to know about the universe today is that there's sort of an average distance between galaxies, and that's the universe today. As you go forward into the future and the universe expands, all we mean is that we're pumping extra space between all the galaxies. So if you ask where the expansion is happening, it's happening between the galaxies. It's still infinite, and it will be infinite in the future, and it was infinite in the past.

It's just that as you go to the future, we've pumped a little bit more space between every galaxy, and if you think about what that means as you go back in time, that means you're sucking space out between the galaxies. It's becoming denser and denser and denser, perhaps still infinite, but eventually you get to the point where everything's on top of each other.

And that's what we call the Big Bang, the point where things are all so close together that there isn't space between them. It could just before that have still been infinite. So in some sense maybe it shouldn't be called the Big Bang. Maybe we should call it, you know, the Big Soup. I don't think it would have caught on.

FLATOW: That was a derisive term, actually, when it was first used.

PERLMUTTER: That's true.

FLATOW: It was - what was his name, the British astronomer?

PERLMUTTER: Hoyle.

FLATOW: Hoyle, right. He said oh, it's a big bang, you know, derisively he called it that, and it caught on.

PERLMUTTER: No, no, exactly, and somehow, you know, we've turned into this, you know, grandiose, you know, image of how the universe could be.

FLATOW: But was that a satisfying explanation to you? I mean...

(LAUGHTER)

FLATOW: I mean don't you want to say, well, it's still some edge on it somewhere, right? Isn't there an edge, if it's expanding, there's got to be an edge to something?

MARY: Well, I understand the image of, like, an expanding balloon. So if there are spots on the balloon that the space in between the spots expands as the balloon expands, and it contracts, you know. At the same time, there's still an edge.

FLATOW: So that's a problem.

PERLMUTTER: Right. Yeah, for me, I've always been bothered by the balloon analogy, although I know why people use it. But for me, it always comes with this image of some - you have to, you know, inflate the balloon into some space. And then that really makes you start wondering, OK, so we need some extra dimensions beyond what we see to - and so I think it's just easier to just face the fact that infinite space is already mindboggling, right.

(LAUGHTER)

PERLMUTTER: You know, before we even start talking about expansion of infinite space, just stop right there and say, you know, how can space - you know, what does it mean to have infinite space? And our brains just aren't up to it usually. But if you let yourself believe that it goes on and on and on forever in all directions, you know, then this extra little quirk that you happen to be able to, you know, add extra distances between things, you know, in between all the spots isn't as bad as that first stunningly impossible idea of infinite.

FLATOW: I'm going to actually make this even more complex and more interesting because I'm going to bring on a seasoned astronomer, someone who's been investigating that same expanding universe but in a different way. Jill Tarter has spent the last 35 years searching for the signal that would answer one of the most profound questions of our time: Are we alone in this big expanding universe? Is there other intelligent life out there? And her commitment to that search has earned her two public service medals from NASA, a 2009 TED Prize and a spot on the big screen.

You may recall her work was the inspiration for the movie "Contact," in which Jodie Foster played a scientist searching for intelligent life in the cosmos. She's the Bernard M. Oliver Chair for SETI Research at the SETI Institute in Mountain View. Welcome back to SCIENCE FRIDAY.

JILL TARTER: Thank you very much, Ira.

FLATOW: How many times a day do you get asked about Jodie Foster?

TARTER: Not enough.

FLATOW: Not enough, OK.

(LAUGHTER)

TARTER: It was a great pleasure to work with that very smart lady.

FLATOW: Yeah. Tell us where are we in the search for extraterrestrial life.

TARTER: Well, suppose, Ira, that your question was: Are there any fish in the Earth's ocean? OK? Not is there extraterrestrial intelligence...

FLATOW: Right.

TARTER: ...but are there any fish in the Earth's ocean? Here's an experiment I'm going to do. I'm going to take the glass of water that you have down on that floor, about eight ounces, and I'm going to actually take the empty glass and dip it in the ocean, and I'm going to look to see if I caught any fish. That experiment could work. There are fish that would fit in there. But if I didn't see any fish, I might be unwilling to conclude that there are no fish in the ocean.

FLATOW: Right.

TARTER: Well, that's where we are with SETI. If you take the entire space, space, this entire multidimensional space that we can envision some evidence of someone else's technology existing in, and you say that volume is equal to the volume of the Earth's oceans. What we've done so far is explore one eight-ounce glass.

FLATOW: Wow. Does listening to what Saul Perlmutter does about expanding universes make - give you hope that there is more life or...

TARTER: Well, actually, let me be a little bit of a spoiler here. Let me remind you that Arthur Clarke once said that any sufficiently advanced technology would be indistinguishable from magic. Might it be indistinguishable from dark energy? Might what you're seeing actually be some manifestation of an extraordinarily advanced technology?

PERLMUTTER: I think it's clearly a fair question. And since we're still trying to figure out just these, you know, baby step understandings of the cosmology that we live in and we know that each of the major steps we've made has introduced some new part into the story. It's - we're still open to the possibility that there's something else even more extraordinary than the story. Now, you know, I think that - I'm...

TARTER: It wouldn't be your first choice.

PERLMUTTER: I was going to say I'm...

(LAUGHTER)

PERLMUTTER: To be honest, I'm more worried that I'll never get a chance to explore what some other intelligent life is doing in the universe. And so I'm - I think that would be wonderful. But I'm - if I had to make a bet, I guess, I would give it less odds.

FLATOW: This is SCIENCE FRIDAY from NPR. I'm Ira Flatow talking with Jill Tarter and Saul Perlmutter. Jill, you're no longer doing the active search yourself, right?

TARTER: No, I'm doing what's absolutely necessary for the search, which is trying to find money to continue the search.

FLATOW: Ah, yes...

(LAUGHTER)

FLATOW: ...we know all about that in SCIENCE FRIDAY also. Yeah. And how does the search happen? Describe how you do - how the search is actually done.

TARTER: Well, at the moment, there are two technologies that we're using. We're using optical telescopes and radio telescopes, and both techniques are looking for signals that represent something that nature does not appear to be able to produce. So if we find them, in the optical, we're looking for very bright pulses of light that lasts a nanosecond, a billionth of a second or less. In the radio, we're not looking for time compression. We're looking for frequency compressions.

So we're looking for radio signals that occupy only one channel on the radio dial where nature spreads its energy over multiple channels. It's - it doesn't seem to be able to be this coherent. So if we find either of those artifacts, we can presume technology, or maybe it will turn out to be some sort of astrophysics that we didn't think was possible but in fact is.

FLATOW: Were both of you always interested in physics and astronomy and science when you were kids? Did you have a mentor? Did you have someone who encouraged you as youngsters?

TARTER: Well, I decided at age eight I was going to be an engineer. It was kind of a thing because the only engineers I knew were men, and I said damn it. Women can be engineers too. And that's the way I went.

(APPLAUSE)

TARTER: And I was helped by the fact that Sputnik came along, and suddenly, we needed more scientists and engineers. And, well, OK, some of them can be women, right? So I went that direction. I soon decided that the more interesting questions were in the realm of physics and astrophysics.

FLATOW: Saul, you?

PERLMUTTER: Yeah. I guess, I was one of these kids, I guess, who wanted to know how everything worked, and I think I remember sort of feeling like here we were in this world where we seem to be held up by the floor, and, you know, and we don't fall through. And you would imagine somebody would have given us an owner's manual that there should be some, you know, instruction book that goes along with all this. And I remember thinking that everybody would need that owner's manual. And I little by little started realizing that, OK, most people and including myself, you know, eventually managed to live in a world where we...

FLATOW: Right.

PERLMUTTER: ...don't get to know how it all works in some - in a deep level, and yet, I still wanted to know is, you know, what could you actually learn?

FLATOW: Yeah. Let me see if I can get a quick question from the audience before we go to the break.

UNIDENTIFIED MAN: I'm kind of interested going from the very small to very large, how do you describe the mathematics of the infinite? Going very large, I can see powers by powers. What does it mean to go infinitely small, and how do you mathematically calculate that backwards trace back to the infinitely small?

PERLMUTTER: I mean, this is one thing, of course, that mathematics makes really easy, right? I mean, it's very easy just to write down a larger number in your exponents, you know, instead - and you could go big by writing, you know, ten to the, you know, 120 as I just did. You go small by writing tens of the minus 120, right? So it's - and so that, you know, is trivially easy for math.

But what's interesting is that what we start to - what the theorists have started to do is actually asked questions like, can you go, you know, infinitely small? Or will it turn out that there is some limit and that you actually have to consider a world in which the smallest units are of a finite size and that they, you know, are very, very, tiny of course. And so there are theories now that are being built on that very question: How far can you take it to the smallest? So far, I have not heard theorists worry about how far you can take it into the large because we know that we're limited how long it takes for the universe to, you know, let light reach us.

FLATOW: All right. We're going to have to break there, take a break. We'll come back and talk lots more about the universe, extra big, the extra small, the search for life. Stay with us. We'll be right back with Saul Perlmutter and Jill Tarter - sorry for my cold today - after this break. Stay with us. I'm Ira Flatow. This is SCIENCE FRIDAY from NPR.

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