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Astronomer Saul Perlmutter shared last year’s Nobel Prize for Physics with Brian Schmidt and Adam Riess. The three used data from exploding stars or supernovae to show that our universe is expanding at an accelerating rate.
But Saul Perlmutter’s head isn’t always up in the stars, he’s also fond of places like San Francisco’s Exploratorium Museum where he takes his U.C. Berkeley physics and music students. Here & Now producer Emiko Tamagawa caught up with him there last spring.
An edited transcript of the conversation is below.
Emiko Tamagawa: Why do you like to bring your students to the Exploratorium?
Saul Perlmutter: For me, it’s what every science museum should be and maybe even every museum. I mean the idea of a place where they really want people just to interact and play and try things out just seems to me the way you should approach the world. In my class I try to do a number of these things but of course the Exploratorium has come up with these amazing ways of showing lots of ideas that otherwise I don’t think you’d ever get to do.
Physics to a lot of people is something that they can’t really see or touch. It’s in fact a subject that lots of people avoid like the plague, so what are the things that you do to make it approachable to people?
I think one of the problems for many people is that the math gets confused with the science and the approach to the world that you learn as a scientist. So what I really am interested in is sharing and having a sense that everybody gets a chance to play the same way that we get to play with the world as scientists and you don’t need math to do that.
With sound you actually get a chance to experience many of the things that you’re talking about but you can actually just feel them. As you walk around the room you can hear acoustics, you can hear what’s going on with the instruments when you pull and stretch a string or when you shorten a string. All those things are actually much more visceral and direct than the math itself, and in some ways they help get at the kinds of questions of how you tell what you know and what you don’t know. For me a lot of what science has to do with is recognizing the things that we’re good at and the things we’re bad at and being able to catch ourselves making mistakes.
Do you remember when you were first pulled by science or was that something… as long as you can remember?
As long as I can remember I’ve always been somebody that just wanted to know how everything worked and I remember always feeling like it was a little shocking to me that we all lived in this world that worked in such an organized way. That you sat on a chair and didn’t fall through, that gravity was pulling you down not up… you know it just felt to me like it’s all so organized. Somebody should’ve given us the owner’s manual… how is it that we’re all wandering around this world of ours and nobody’s given us the rules of how it works? So, I always thought that we all needed to know that. As you get older you start realizing that ok, you actually do pretty well without really understanding how it works and most people aren’t as obsessed by knowing what the owner’s manual is as I was, and still am at times, but there is still a real pleasure of understanding what’s going on.
Can you explain very simply… you looked at supernovas to look at the nature of the universe, and this is the sort of thing that makes everyone go huh?
Way back in the 1930’s, Hubble had measured that the universe was expanding and ever since we knew that we’ve wondered is that going to go on forever or is it slowing down? I mean you might imagine that it would slow down because everything gravitationally attracts everything else, so we’ve always wondered about that and it was only in the past few decades that we’ve realized that actually you could go out and measure the answer to that question.
It was because we recognized that there was a type of supernova called Type 1A Supernova that you can recognize by its particular colors, it turns out to always be exploding about the same way. They brighten like a firework and then they fade away in a few weeks and at that peak brightness they’re always about the same brightness. And since they’re the same brightness you can measure how far away they are just by measuring how bright they are at peak. That tells you how far back in time that particular supernova exploded. And then the only other thing you want to know is can we tell how much the universe has stretched since the time of that particular supernova’s explosion. It’s very easy because the supernova gives off most of its light looking blue.
While the light travels to us it gets stretched. That wavelength gets stretched just as the universe gets stretched. By the time it reaches us, it looks pretty red and how red it looks tells you exactly how much the universe has stretched. So what we did is found supernova that were different brightnesses, that means different distances and different times back in history…From each supernova we looked at the color that the supernova had now been stretched to looking and that tells you how much the universe has stretched at each of these different times. We thought that we were going to find out that it was slowing down, and of course the big surprise that we found was that the universe is actually speeding up.
Where are you exploring now?
What we’re trying to do now is design a whole bunch of new experiments and new projects, including some more using supernova, that will allow us to make a very detailed measurement of how it was that the universe went from the early period in which it was slowing down to the current period in which it’s speeding up. Perhaps it’s not another dark energy at all. Maybe it turns out that we actually need to change Einstein’s theory of general relativity.
Einstein’s theory of gravity might need a modification which would be really amazing. I don’t know which one’s more amazing that you have to change Einstein’s theory of general relativity or that most of the universe, almost three quarters of the universe, is made out of the stuff that’s this dark energy that we’ve never explored before.
So does it still get you as excited as it always does?
It’s a great topic. It’s a great set of projects. It makes you feel like we might be on to something really deep and fundamental about how the world works, how the universe works. There aren’t that many times in history that you get to play with these kinds of deep fundamental ideas and perhaps get to the bottom of them by just making measurements.
Ok, I have to ask you the one stupid question. So how was it to actually get the call that “Hi, Saul Perlmutter, you’ve won the Nobel Prize?”
Well first of all, in California it’s the right place to win the Nobel Prize because you get the call at a very dramatic time of night. It comes at about quarter of three in the morning. So I woke up from a deep sleep and as I reached over to pick up the phone and the person on the other end said to me you know is this Sal Perlmutter and I said yes and he said how do you feel? And I said fine thanks, why do you ask, and they said you know about the prize… and I said well I actually hadn’t heard about the prize.
It turned out that the Nobel Foundation and the Swedish academy who were trying to reach me had some wrong numbers for me. So it wasn’t for an hour later that I actually got the official call, so my first calls were from some radio reporters from Sweden and they actually ended up just looking it up in the phone book.
It was pretty cool?
Oh yeah, I turned to wife after managing to get off a stream of phone calls and realized that I couldn’t answer the phone anymore, and it was now three in the morning, and I said you know I guess we’re not going back to bed. And then within a half an hour probably there were all the television reporter trucks outside the house with the bright lights and the staff from the university showing up to try and manage everything. It was just a fun day because we ended up having a chance to celebrate with a lot of the other people who were involved with the project at the university, so it had a nice group feeling.
Yeah but now you go back to work, so that’s a good thing too.
Exactly, you wouldn’t want to run around all the time celebrating, you know, just Thursday afternoons