Interview with the 2011 Nobel Laureates in Physics Saul Perlmutter, Brian P. Schmidt and Adam G. Riess on 6 December 2011.

Adam Riess, Saul Perlmutter, Brian Schmidt, welcome to Stockholm. I gather that this year Stockholm is making itself the city of lights for Christmas which seems very appropriate as a way to welcome three astronomers to the city.

Brian P. Schmidt: Yeah, as long as we are not looking at skies, I think it will be great.  

I suppose that one could make some complicated joke about the pace of the recession and all these lights and the astronomers, but we won’t go there. You are here because you made this remarkable discovery about 15 years ago, that the expansion of the universe is accelerating and up until that point people had thought that the expansion of the universe was either preceding at a steady rate or might be slowing down. And yet this remarkable discovery was welcomed by the committee, people didn’t say ”No, this can’t be” but rather they said ”Yes”. Why? Why did they accept it?

Saul Perlmutter: I think it was in this particular case there were two things going for us, and I will say one of the fastest acceptances of a breakthrough question, breakthrough issue in science topic. But the two things where one is that there were two teams that were gaining these results so the fact that both Brian’s, Adam’s team and my team were saying the same things and we were known to be in a very tough competition with each other and that we would have been very happy to call each other out, make a mistake. That, I think, was one of these cases where they got an immediate confirmation instead of having to wait for the years it would often take for another team to make a confirmation. That was one of the practical aspects of it. There was also a part; it certainly made a lot of other problems fit, so suddenly things fell into shape. I am sure we had all been hearing many complaints and worries about how is it that the universe is younger than the oldest star and these other issues that were floating around and suddenly those went away.

Brian P. Schmidt: There was a very strong theoretical view of how the universe should be. As an observer I just said ”They have it wrong” but it turns out this theoretical view of what the universe should be like was sort of confirmed by the observations of the accelerating universe. That section of the community I think were very happy to see it. Whereas the observational side, the people who actually go out and make experiments like to have things be as simple as possible. I think it was more skepticism on that side but the joint teams finding the same thing I think helped erode a little bit of that skepticism from that side of the community.

Adam G. Riess: Just to follow up on what Brian was saying with this theoretical preference. The preference was that there would be a certain amount of energy or matter in the universe and so we kept looking for the matter. After a while of looking we could only find about 30% of it, there was a hook that if we looked further out, we would finally find it. We didn’t but what we found was the other 70%. It was in a funny form, this funny kind of energy that we call dark energy. As difficult as it was to understand some theorists were kind of happy that they said “Well, anyway you complete the picture, we are happy to get to the 100%”.

Saul Perlmutter: I mean, it is funny because I think there was one group of theorists that I think were telling us ”Why are you bothering to do this measurement when you already know what the answer is going to be” whereas most of the observers in the world at that time would say ”Well, you can’t trust the theorists, they have been telling us all sorts of things that turned out to be wrong once we actually did the measurement.”

Alright, yes.

Saul Perlmutter: But then finally there was another whole set of theorists who I think were worried about our result which were the particle physicists who have to explain why this dark energy, or if that is what it is, a cosmos constant/, was so small when the naïve theoretical calculations would have given you something 10 to 120 or 10 to 50 times bigger. They were still left with a problem, but I think in the end they had to go along with everybody else’s understanding.

Brian P. Schmidt: Just to be clear, those people had a problem because their view of the universe was that the universe should never allow us to exist anyway. We should have went ‘puff’ and down the acceleration a long time ago so we would never have been able to have humanity on it. So then they just had to say ”Well, something happens to cause this problem to cancel out so there should be no dark energy at all.”

Saul Perlmutter: They would have been happy with zero or they would have been happy with saying that we couldn’t exist, but they weren’t happy with our number.

Adam G. Riess: My thinking has evolved on this a little bit. When we first found this result and the amount of dark energy was not zero, I thought naively we had created a problem, by having this they would have to explain it. But then I came to understand that they had no good justification for it being zero and that we had not made the problem worse or better, we had just shined light on the problem.

Brian P. Schmidt: I think we have made it harder because they could imagine that thing A and thing B would cancel each other out. That you can subtract A from B and get zero. But when you subtract A from B and you get a number that is a 120 zeros, 1 different – that is hard to do in physics, it turns out. And that is, from their point of view, what we have done. I think from our point of view we probably didn’t do that – it is something else going on.

Adam G. Riess: I think at that point it becomes a matter of taste sort of. Some theoretical physicists have this taste that zero will be, even without knowing them how to get there, zero will be easier. Others say ”Well, there has been plenty of symmetry breakings before”. We have matter not antimatter even though those were very close maybe this 120^th last number won’t be hard.

Saul Perlmutter: What actually surprised me in all this discussion is that nobody seems to be relating it to the fact that we already have this other part of the story – this inflationary part of the universe story, where in the first fraction of a second the universe is supposed to have undergone a huge rapid acceleration. And then that decay away and we got the universe that we now see that first decelerated and then accelerated. But that also requires an explanation and you have to put in new elements into the physics and people were perfectly comfortable with that and yet they didn’t seem to be comfortable with giving us the new elements of physics in the same way. I thought it was kind of interesting.

We will circle back to this again because I want to talk more about dark energy for sure. But just to focus on that moment of discovery, how these two teams in competition, you weren’t talking to each other at all, you were just …?

Brian P. Schmidt: We were talking to each other, sometimes civilly sometimes not so civilly.

Adam G. Riess: About … we would need telescopes or …

Saul Perlmutter: Lots of practical things we had to figure out together.

Adam G. Riess: We were not analysing our data together, we were keeping that separately.

You have described it before as the slowest ‘Aha’ moment in history perhaps, but you were coming to this realization that you were going to have a result that you were not expecting. How did you individually deal with it because the world welcomed it when it came out but as you were analyzing the data and beginning to see that this result … were you doubtful, were you thinking this is not what we should be seeing, there is something wrong?

Adam G. Riess: I just thought it was wrong, but just it was going to be wrong for a simple or done reason. We would say a math error or any sophistical analysis that usually means a bug in a computer program. But that it would be wrong for that reason and as it evolved I started thinking maybe at least it is wrong for an interesting reason, something you know we won’t kick ourselves and say ”We should have known that”. I am pretty amazed that it survived to this day at face value of what we thought it was.

Saul Perlmutter: I guess there is the other element which is that there is a chain of analyses that we all have to do and many steps in that chain you have to calibrate. In the very first days of the measurement when you first put the chain together you often put the chain together and put the point in the plot just to make sure, to show that the chain all holds together and works. And then you plan to go back and fix, tune each of the different calibration steps along the way to make sure that you got all your i’s dotted and your t’s crossed. We also, I think, in the very early stages thought that, as we started to put back all the calibrations, the plot would home in to something more sensible and of course as we did those checks, it just homed in more nonsensible.

Adam G. Riess: I think the flavor of our analysis was different. I think we had our tool kit and we were going to take the data through that and see the answer at the end. And when we saw it, we were kind of stuck only with ”Maybe we made a mistake” …

Saul Perlmutter: So you had pre-calibrated everything?

Brian P. Schmidt: We had pre-calibrated everything. We really just wanted ‘dun, dun, dun’ and then ‘katching’ and you were like ”Oh, that is not so good, let’s go through each step again and what went wrong?”. So that was me, I just said ”Ahh, alright where did we mess up?”

Saul Perlmutter: But you should say that most what a scientist does, I think, is look for your own mistakes. That is not unusual, that you are spending a lot of your time trying to figure out ‘Is what I have done today correct? Is what I did last month correct?’ Sometimes this notion that you get asked the question What did you set out to prove? I don’t think any of us set out to prove anything in these things. We were just going out to make a measurement and making measurements are hard.

Brian P. Schmidt: We were trying to prove was the universe slowing down a little or was it slowing down a lot. You had gone through the idea of testing this, we knew we could do that but I kind of figured that that was a irrelevant question. Indeed, I was a referee of a paper he did where he asked this question and one of my comments as a referee was ”Fine, but it is not” … There was a figure where if the universe was not accelerating then we couldn’t really show too much about how much of this dark energy there was. What I had ignored was if the universe really was accelerating you could actually tell that. So, I went in with such a strong bias that I said ”This is an irrelevant experiment cause it would have been. If the universe wasn’t accelerating, we wouldn’t have been able to say anything interesting”. But I had failed to grasp that if the universe really was weird the experiment could show that. I was a bad referee.

One last quick question about this discovery moment – did you check with each other? Because you knew the other team was working, you didn’t ring each other up and say ”Look, hey” …

Brian P. Schmidt: Oh no, quite the opposite.

Saul Perlmutter: So now was the point in which we all wanted to see what could we say? And you didn’t want necessarily to tip your hand to the other side.

Adam G. Riess: I think we learnt about each other’s results from conferences.

Right, okay. That must have been a great sense of relief and excitement.

Brian P. Schmidt: Well, it provided I think to both teams a great sense of urgency as well, because suddenly ”Wow, we …!” Truth be said, we thought we had different answers up until, in our case, the very last minute so that was one of the senses that we were rather concerned about our results, we genuinely thought we were getting a different answer than they were.

Adam G. Riess: I also suspect none of us felt full relief seeing the other having the same result because at its core we are both using the same tool, the supernovae, and that all that would have meant in that point was something in the supernovae had fooled us. I think we probably all felt much bigger relief in by around 2000. And that is when I went ”Oh my God, it is the face value.”

Brian P. Schmidt: The cosmic microwave background measurements were able to essentially sum up all the matter in the universe. The only way that was going to work was if our result was correct. So at that point our result went from being ”Yes” to ”There is no way this could be wrong”.

Saul Perlmutter: There are typically one big loophole that is left over.

Back to his point about scientists trying to prove themselves wrong. You got this current ongoing example of the faster-than-light neutrinos where people are saying ”This is what we are seeing, tell us what we are doing wrong”. That seems to be exactly the way that people should behave.

Brian P. Schmidt: I think it is a great experiment. It is a great experiment to try. And I think like most of us, we are hoping it is right but are dubious, just like people were dubious with us, so I think they have done the right thing and they have been cautious about it. Reality is, I think, they were struggling to get the resources to replicate the results to do things and by elevating its insignificance they now are able to check it in a meaningful way.

Adam G. Riess: But I would say that today they are in a much weaker position than we were in the spring of 1998 in that they are not two teams that has found this result, there is only one, so they still need to replicate it. There is a face value at least some evidence that there is a better constraint or measurement on this effect.

Brian P. Schmidt: A conclusion coming from our subknown field.

Adam G. Riess: Right, and finally it doesn’t fit a picture so neatly as it turned out dark energy or acceleration did, it actually may create problems. It doesn’t mean it is wrong, it just means they have a higher hill to climb that we did, I think.

Yes, indeed. Okay, so we do apparently live in a universe that is speeding away from itself faster and faster. Does that mean that that will never stop, can we say that yet? Can we say that it is just going to carry on accelerating or do we not know?

Saul Perlmutter: Until you understand why it is accelerating today, you can’t really make good predictions about what it will do in the future. Particular if one of the answers is true, if it turns out to just be a cosmological consonant as Einstein had put it in the equations then you would expect it to go accelerating forever. But if it turns out to be something more like the clause of that very first fraction of the second acceleration in an inflationary universe, we know that decay away. And then it would turn into a deceleration after that and in which case this one could perfectly well decay away and we could be left with deceleration in the future. Until we have evidence that will point us to which explanation is right, I think it is going to be very hard for us to make our, what we would thought was going to be very solvable prediction for the fate of the universe when we are all set out for this.

Brian P. Schmidt: Although that being said, that’s being ultra-cautious. Okay, it is an ultra-cautious statement. The simplest part of what we have measured is that it is not decaying away right now, so it is behaving very much like Einstein’s cosmological constant which is energy fixed with space. Although a theorists could make the universe do a right turn and turn on a very small piece of ground, that is not a simple explanation. The simplest explanation is yes, that the universe is going to keep doing this for long enough that it will sort of make the universe disappear from us. That is the simplest explanation. It is not iron cloud but I would probably wind up bet some money on it, I would certainly wind up to bet my hamster on it.

Do you have a hamster?

Brian P. Schmidt: No, I don’t.

Adam G. Riess: If he loses the bet, he will have to get one.

So how close are we to saying anything truly meaningful about dark energy and what it is, if dark energy is the all-embracing term for what it is that is pushing the universe apart? How close are we to knowing?

Adam G. Riess: There is sort of an observational and theoretical answer to that question. I think what we all are hoping is that a deep theoretical idea comes along, sort of like when Einstein revitalised gravity with his general relativity. That people say ”Wow, oh my gosh, that has to be right and that explains everything.” And I think we can learn at this point far more about dark energy by that path if it happens, on the other hand you can wait around forever and the next Einstein couldn’t come along. Then we are collecting these observational clues and the biggest clue is, as Brian was describing, if we could test and actually rule out that it is Einstein’s cosmological constant. If we do see a changing with time another possibility is that we saw the behavior of dark energy changing on scale. Changing when you look on the scale of clusters of galaxies versus the whole universe. If you saw different behavior then you might expect that there is a scale, we say scale dependence, which would mean general relativity which has no scale dependence, might not be the right theory.

So that is a case of making finer and finer measurements then.

Adam G. Riess: That’s right. And when you do that you can never tell when suddenly you are going to say ”Wow, what we thought was the right answer has fallen outside of our confidence”.

Brian P. Schmidt: And it is not just finer measurements, it is also different types of measurements. There is the finer measurement of just ”Does the universe behave exactly like what Einstein’s cosmological constant say?” But then there is going looking and saying ”Well, let’s try”. We always look at how gravity works on the scales of galaxies and on the larger scales, we looked at larger scales, we got an answer which is funny which we can explain with dark energy maybe. But maybe we want to go to that intermediate scale which we haven’t ever really looked at much before and we want to see what answer we get and say ”Is that consistent with dark energy?” or is it a little different than dark energy indicating that dark energy is the wrong explanation.

Saul Perlmutter: When you ask what are the odds that we are going to get somewhere – we are waiting for that ‘Aha’ from the theorists, but I am hoping that if we give a new, one next level of gather about the properties of the behavior of both the history of the expansion and also the history of clumping of matter within the gravity, the effects of gravity. By doing those will home in a certain range of possible answers that will help the theorists have that ‘Aha’ moment. That is why I am actually a little bit optimistic because I would say that whenever you get a whole new set of data that brings light to an area that hasn’t have had data there is a reasonable and fair chance that some theorist would have a ‘Aha’ moment when they see it. And cosmology isn’t that old a profession in this position, domain, and so we have only had a few big pulses of new data and each time we have also had a ‘Aha’ moment. Each time is has given us something new so I think we should, there is a reasonable chance that we get one more big pulse of data, we might still have another ‘Aha’ moment. You need a couple of rounds of boring moments before you give up on that approach.

Unless you design your next experiments, how much interplay is it there with the theorists? Are the theorists dictating where you are going or are you basically just …?

Saul Perlmutter: They are not giving enough direction where to go at this stage, so far they are just telling us “Just give us something to go on” and they have been laying ideas all over the terrain in case we happen to go in that direction with our data.

Brian P. Schmidt: But they are haven’t really given us a lot of space to go through brilliant new ideas: ”Try this!” We really are kind of feeling our way through the dark at this point and it has been a little, it is a bit frustrating I guess , it is frustrating for them too because they just keep on beating their heads against this brick wall, it is like ”Why is this stuff there and no one really has got an insight?”

Adam G. Riess: In fact, I would even go further, some theorists have actually reached an explanation or point where they would say it is beyond our ability to measure. Many theorists now subscribe to this point of view that there is a multiverse – there are many disconnecting universes. Each with their own value of this dark energy and that rather than being able to understand a deep reason why ours is as it is, nature rolls the dice every time one of these universes is born. We got a value that is reasonable enough to allow life to form and the disappointing thing to us experimentalists is there is no prediction. There is no experiment, there is nothing to say “Well, if that is right then we ought to go look for something” so that is almost the opposite of helpful.

Brian P. Schmidt: Well, it is a metaphysical argument.

Saul Perlmutter: Some say that we probably won’t really accept that theory, or that set of theories until they do provide some prediction that we can go test as a …

Brian P. Schmidt: One would hope that idea of there being millions or billions of universes out there, that there would ultimately be some prediction in our own universe that we could make.

Saul Perlmutter: Or else it is just philosophy here.

Adam G. Riess: Some say they are satisfied enough that it is Einstein’s cosmological constant, that we should stop, we will never find evidence. I think our view as observers is any time we can think of an experiment to look at the universe in a way it hasn’t been looked at before or to a precision that it hasn’t been looked at before: it behoves us to do that because after all, in 1998 we were pretty surprised. We didn’t listen to people who said …

Brian P. Schmidt: “We know the answer” that’s right.

So, for the moment you just hope that the multiverse people aren’t sitting in the funding committees deciding whether you are going to do the next experiment.

Saul Perlmutter: They are actually pretty good themselves. As individuals they will all say “No, but you should go out and make measurements, don’t listen to us. Right now, go out and measure something.”

Brian P. Schmidt: But eventually, I mean it just comes down; you look, and you don’t know what the universe … we don’t know where the truth lies. You really have to go out and look but at some point, looking becomes extremely difficult, extremely expensive and we are not there yet, but we might be getting close in the future. I think we need to grow and do the best experiment we can and then at some point it will become less interesting if we don’t find anything but we don’t know that until we are actually there.

I wanted to ask about the climate for doing your research because in these days when there is a certain amount of cutback on space research, is it the same for astronomy or is astronomy in a flowering time?

Brian P. Schmidt: I think it depends on where you are at. For example, United States and Australia are at very different spaces right now. Australia is spending lots of money on astronomical research fundamentally looking at the square kilometer ray, which is a next generation radio telescope which the government is very excited about so they have put quite a bit of effort in. Maybe you guys want to explain the US situation.

Saul Perlmutter: Of course. I think the US world at this moment happens to be a pretty difficult political scene to try to build anything new and in general of course people are mostly focusing on cutting back at this stage, but it is also true that during times of cutback often you need to try to figure out what are our prime targets? Is there some area where we should make sure we don’t lose that field and I think maybe people are optimistic that things like this Nobel Prize and actually there have been a number of very influential decades of survey style reports will help focus funding so that it will at least preserve some of the fields that are looking very brightly at the moment.

Adam G. Riess: I think the key word is focus for the US portfolio now. I mean we are finishing building the James Webspace telescope which is going to be a big large flagship like the Hubble space telescope but that may be the last of its line. And everything after that is going to have to be focused and smaller scale and targeted, and I think we are hoping that dark energy falls into that camp. It was the number one recommendation of the decadal survey to build a focus mission on dark energy. The Europeans are also planning a mission like that as well.

In Australia presumable, there are far fewer Nobel Laureates of course and a far smaller population and so, but you are the first physics laureate in Australia for a very long time.

Brian P. Schmidt: Yes, since the Braggs in 1915. And you know, Nobel Laureates follow a worthy investment societally, so Australia has invested a lot in immunology and medicine, so we have quite a number of laureates in that area. But in physics it is done a lot in astronomy but less in other areas so the fact that they spend a lot of money in astronomy is not surprising that someone like myself was able to make a breakthrough because it is a great place to work in.

And did you move to Australia for that reason?

Brian P. Schmidt: I moved there for a variety of reasons at the end of graduate school where it was a good place to do astronomy, it was a good place for my wife and I to have the family and to work on our various careers together.

Saul Perlmutter: It wouldn’t have been as easy to go if it weren’t for the fact that there was already a place on the map in the field.

Brian P. Schmidt: Certainly true, the reason I was willing to go to Australia was specifically because it had 50 years long time of lots of investment in astronomy.

Saul Perlmutter: I had already spent time in Australia for the astronomical observations. It was clear that it was a place, it is not that many places in the world that are such players and Australia was.

You mentioned frequent flyer miles before we started. Does travelling around the world take up a lot of your time?

Brian P. Schmidt: Specially in Australia, it is a problem. We have all to go to observatories and things, I mean Adam is more of a space telescope guy, but he does go observe as well. Saul and I will know tripsing back and forth to observatories and to meet your colleagues. It is a very international field so, but all of our teams had people on I think five continents between the two of us so you can only do certain much on the phone. At some point you got to get meet people in the flesh and get stuff done.

Saul Perlmutter: Besides this amazingly interactive social human activity you really have to talk together and work together. It is funny that still video conferencing isn’t good enough.

It is also funny the sort of perception of the non-scientist of the scientist is still very much of the lonely figure. It is not seen as a mixed society.

Saul Perlmutter: I would hope that if anything would come out of all the discussions that we get to do as Nobel Laureates is that they would understand: if you want to do anything social, you shouldn’t go into any other field, you should go into science. That is the place to be with people.

Adam G. Riess: And the work is very distributed, we can, because of the nature of it, we can distribute our digital files or what not across the internet. With new tools, with video conferences and you can always be in contact at some level.

Brian P. Schmidt: And at a launch you work on a problem 24 hours a day which sometimes is more useful than you think. People in Europe, US and Australia, you can just keep a paper going around and you can get things done really quickly.

Does you work lend itself to this cloud approach where you just put it out to humanity not just the specialists, but you allow other people to get involved?

Saul Perlmutter: It hasn’t happened that much yet except in one particular domain which is that the average astronomers have been quite successful over the years in supernova work. They were the ones originally who found the supernova for us. Today, there are these things as galaxy zoos where they distribute images and then they let the world go loose on trying to classify things, so that particular area happens to be very successful. Some supernova research has been done that way.

Brian P. Schmidt: I am actually with one of my new surveys going to be using that because I don’t have the capacity to find things really quickly and confirm them, so we are going to be crowdsourcing, as they say, so people will go through and for example when we are looking at nearby galaxies and we have a supernova go off that is really young like hours old. Rather than me wait up in the morning and see if it is real before I start telling everyone the crowdsourcing can do that for me so it is our hope that we can use that.

That seems like a wonderful way of engaging people in the pursue of astronomy.

Brian P. Schmidt: It seems to work pretty well with a certain selective group of people. It is quite exciting. Some people have become quite obsessed with it, you got to manage that part.

Saul Perlmutter: I know my colleagues, another one of the project I am involved with, put up a site just to try it out to see if it would work for supernova searching and I think within the first 24 hours they had over a thousand man hours of effort that had gone into it and it wasn’t advertised or anything, it was just …

Adam G. Riess: I was just going to ask you did you advertised it or?

Saul Perlmutter: No, it was sites where you knew you could find things like the galaxy zoo and instantly there were thousands of hours spent on something that we couldn’t have paid anyway to do.

Brian P. Schmidt: We have a responsibility to make sure it is interesting though. We want to make sure it is interesting work we do and there are things we can’t do otherwise. But it is an interesting point of outreach where we can really work together.

And on this subject of engagement, I was interested what made you become astronomers in the first place? Because everybody on the planet spends time looking up at the stars wondering, few make that their lives. But I would think lots of people would think it was a very appealing thing to do. What made you do it?

Brian P. Schmidt: In my case I always knew that I was going to be a scientist – my father was a scientist and I loved science. What made me go into astronomy itself – well, I didn’t really know what to do when I finished high school, I had dabbled in astronomy, I hadn’t done a lot of it, I dabbled in it. And I suddenly realized that I had to figure out what I needed to do at university. I said “Jeez, I don’t know what I want to do! What would I do for free? Hm, I would do astronomy for free”, so I figured I would start my astronomy career figuring I would get trained up and I would ultimately do something else, so it was really quite a holding paddle for me.

Saul Perlmutter: You already had a backyard telescope experience as a child?

Brian P. Schmidt: I had a little telescope as a child, I was interested in it, but I wasn’t obsessed. You know, some of my friends were really obsessed, knew every constellation, everything. Naw, it was something I did a bit of, but you know very part time.

How about you, Saul? 

Saul Perlmutter: I was not even an astronomy amateur as a child though I was always someone who saw science as something likely I would end up doing. I always wanted to have to work with how fundamental things held together. As I have been saying to people, I didn’t understand how it is that we live in this world and nobody has given us the owner’s manual, how the whole thing fits together and I always read the owner’s manual when I got new toys or a new car, but I just assumed that everybody needed to know these things. Over the years I started to realise that most people get by fine without knowing it. But when I had the opportunity in college and graduate school, I thought I would at least try out this physics stuff and see whether I could enjoy and make it work.

But that was physics and then astronomy?

Saul Perlmutter: For me, the astronomy just became one of the more attractive ways of doing the fundamental physics. When I was looking at graduate school for a topic to work on I remember this period I was concerned because I knew I wanted to do something that I felt could be fairly philosophically interesting, that you would actually go very deep. The projects at that time, the most appropriate for that were the big particle accelerator projects. But as a graduate student at least, it didn’t sound like something I wanted to start with because those were such huge teams. I wanted somewhere where I felt like I could be part of a small, you know, bigger part of a small group, as a graduate student at least, to get my feet wet with science of that kind, at that level. Then I realized that period it started to look as if astrophysics could be another way of asking the same questions. I just turned out to be very fortunate that that was the right period to try doing some of these fundamental physics questions with astrophysics. Then I was basically doing astrophysics for the rest of my career.

It is interesting you mention particle physics because that is in a way sort of the great team effort for the 20^th century, now 21^st century, building of a standard model, vast teams involved now. It makes one wonder how in the future one is going to select people for Nobel Prizes out of these teams but anyways let’s not …

Brian P. Schmidt: It is a big question.

Adam G. Riess: I thought Brian would need help, so I decided I went into the field. No, I came into it from physics. I loved physics, I loved these fundamental issues and when it was time to choose graduate school I guess these fundamental questions in other areas of physics like ow hot or how cold can things be didn’t appeal to me as much as these big questions that we can address in the universe and in cosmology: How old is the universe? How big is the universe? What is its ultimate fate? It was amazing to me that with the tools of astronomy one could address those questions that just seemed like questions you just ask philosophers.

Saul Perlmutter: I am just curious, would either of you guys have been as interested in doing more traditional astronomy project?

Adam G. Riess: Like studying objects?

Saul Perlmutter: Yes, understand how does that object work and how is it that that object look the way it does.

Adam G. Riess: Me no.

Brian P. Schmidt: I have done a bit of both, so I studied physics of exploding stars and so – that is how I started out. But I always had an interest in cosmology at the same time so I really came out from a strong baseline.

Saul Perlmutter: So you could have enjoyed either one you think?

Brian P. Schmidt: Oh yeah, I still do. I did physics but that is the physics of understanding how things work rather than … it is actually rather physics-y.

Saul Perlmutter: Yes, that is true too. It is just … it is the physics of how is this part of the story work more than your other interest which is physics of how does the whole thing put together.

So unfortunately we are running short of time but I just wanted to ask before we stop; what do you say to young students coming in to the lab or to the telescope and saying: What should I be doing in the future? What are the good questions? What advice do you give?

Adam G. Riess: Students who are first coming, they don’t know exactly what the best areas to research are so first you do start in the big picture, the high level, you say: You know we found the universe is accelerating but we don’t understand why. There might be dark energy we don’t understand, something about gravity, this is the big question, but I have an idea for you, and it is to investigate this new technique or this way of doing it. I might also ask the student what their skills are, if they are interested in observing, if they are interested in theory or computer programming. But usually it is a marriage of the big picture and an idea I had in the shower last night on a technique and then you know we will see where it goes.

Sounds good.

Saul Perlmutter: I think similarly we often start a new student on something just practical to work on that will give them a sense of feel of the techniques and ideas and how we work. But then the hard part is to translate that, at some point in their work, into something that they can really love. And my sense is that if they are going to go into the field they really have to do science that they are going to get a real kick out of doing because you are not doing this for the money and you are not doing it for the ease of advancement. I mean these are difficult fields to move forward in so first of all you just have to be doing it because you are just having such a good time doing it and because they are having a good time they often become much better at it. I mean that is often the place you get the most remarkable work out of people. So sometimes the hard part is to go from the mundane starting projects to what are you actually going to care about at the end of the day. And we don’t always manage to do that in graduate school, sometimes they don’t get until they come back as a postdoc or something and then they have gotten to the thing they really enjoy doing. But that is at least the goal.

Brian P. Schmidt: In my case, I always go and throw lots of ideas out and try to explain the minutia, what you have to do to begin with and then what the real big payoff would be. I also make sure that they go and talk to other people and try to get the same idea in a completely different unrelated areas and then I always tell them as Saul would say “What grabs your fancy? Go with your gut feeling, try what is interesting for you because you’ll learn”. The whole point of doing a PhD is not to become an expert in a tiny little area, it is to become an expert in thinking about how to solve problems and you will learn that and do better if you do something that you love, as Saul said. So I always try, as I said,  throw ideas out and then let them go for their gut feeling and then work with them to solve the problem but I really make sure they are driving it.

Saul Perlmutter: I think I also like your suggestion that people should feel comfortable with the idea that they won’t know the whole terrain of any area, specially nowadays, it is just impossible to know all the things but they should feel really competent to dive into something and then learn that tool, the tools that they will need in that little area. And I think that is the great thing.

Brian P. Schmidt: That is the great thing that academia gives you; that ability to learn tools, and to learn new tools once you have finished with one problem, you can keep doing it or you can do something else.

Endlessly various. Thank you. Thank you very much all of you. We haven’t even had time to speak about wine which I know is another great passion of yours.

Brian P. Schmidt: I am good at baking and drinking it. I am not sure if he likes to drink it.

I guess drinking it will take up at least a good part of the upcoming days during Nobel Week. Anyways, thank you very much all of you for speaking to us.

Brian P. Schmidt, Saul Perlmutter, Adam G. Riess: Thank you.

Watch the interview

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