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Interview of Brian Schmidt by Ursula Pavlish on 2007 July 25,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
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Brian Schmidt studied as an undergraduate at the University of Arizona, where he worked on discovering supernovae with the CCD Transit Instrument under John McGraw. He continued his graduate studies in Astronomy at Harvard University, with Robert Kirshner as his thesis advisor, from 1989-1993. He stayed on at Harvard as a postdoctoral fellow before moving to The Australian National University in 1995. When he attended a summer school in Les Houches, France, in 1990, on Supernova, he met many of the supernova greats and marks this as his induction into supernova astronomy. Schmidt started the High-z Supernova Search Team in 1994 at the age of 27. He wrote the supernova search software, much of the simulation software, as well as one of several cosmological fitting software used by the team and led them to their 1998 discovery of the accelerating universe. In this series of interviews, Schmidt discusses the spaces of scientific work, supernovae as scientific objects, and scientific visualization. Schmidt’s outstanding good humor is infectious, and he is an astronomer and an observer highly respected within the profession.
It is July 25th. I am here with Professor Brian Schmidt. We are back at Caltech to continue our interview from yesterday. We left off, around the spring of 1997, which was when you decided to designate one group member to be “IT” for data analysis of the group’s work. I would like to ask you, specifically, how did you think up this innovation? It is really an innovation in collaborative authorship. We also talked about software sharing, and about your conviction that science should be conducted openly.
The innovation of doing science this way was out of necessity because we needed to get the papers done quickly. I felt very strongly that the young people, who were going to do the bulk of the work were the ones who needed papers, to get publications so that they could get jobs. We were a very top-heavy group. That is, we had lots of ‘Chiefs’ and very few ‘Indians.’ I wanted to spread things out. Peter Garnavich represented the Harvard group. Adam Riess represented the Berkeley group. Those were the two groups that seemed to have the ability to work quickly and had young people. It was really out of necessity that this came out. We say necessity is the mother of invention. If we had not done it that way, we would have ground to a halt.
Had you heard about this done in other places, in other contexts?
No. It was really born out of watching too many young people be eaten up by big projects. I did not want that to happen. Partially, it was a reflection against the other group, where I saw how all the papers were led by one person. I could see their young people struggling to get jobs. Alex Kim, for example, was doing a lot of work. Rob Knop, who I did not know at the time, ended up with the same type of problem. I knew a little bit about their team at that point, but I did not know it that well. It was really the strong view that we needed to get the young people in the position to become scientists. Astronomy does not work like particle physics. The SCP had a particle physics mentality, which somehow supports that model that they used. But, we were astronomers. Astronomy does not support that model.
Does the SCP also stick to this two cultures view, of you as coming from the Astronomy culture and them from the Particle Physics culture? I heard Adam Riess also characterizing the two teams in this way. I am wondering if it is a shared characterization.
I would not know. My guess is, it depends on who you ask. If you ask the astronomers, they will say yes. If you ask the Particle Physicists they will probably say no, but I am not sure. They have had to evolve more to the astronomy side because they have employed mainly astronomers who have had to swim in an environment, which they were not completely set up for.
There is a bit of an imbalance there, because your team has not recruited any past particle physicists.
We have not, but we are almost entirely made up of people who have worked on Supernovae. We were all Supernova people. Almost all in the team have papers in a wide variety of Supernova topics. That distinguishes us from the other team, which is really focused on this project.
If I may ask a personal question about Supernovae, you mentioned the conference that you attend, the summer school in Les Houches, but how did you first become interested in Supernovae?
As an undergraduate at the University of Arizona, I was working on finding Supernovae in an experiment called ‘The CCD Transit Instrument,’ under the supervision of John McGraw. I had not thought to do Supernovae in graduate school. Certainly, when I was looking at places that was not at all on my mind. But what happened was, I was trying to decide whether I wanted to go to Caltech, to Santa Cruz, or to Harvard. I visited all the places, and knocked it down to Santa Cruz and Harvard. Bob Kirshner came to give a talk, the first Mark Aaronson Memorial Lecture in 1989. He gave a very good talk, which I was interested in. He worked on Supernovae. It was him being there, and my saying, “May I work with you? You are a good guy. It would solidify my life.” He said, “Yes.” That is how I started working on Supernovae. I did have that connection as an undergraduate, but it was not what made me work on Supernovae. It was really Bob Kirshner being there when I could not make my mind up where to go. If I had gone to Santa Cruz, I would not have worked on Supernovae.
There is some contingency there, although historians tend to use that word too much, I think. From listening to our conversation yesterday, I see that we tend to discuss topics on the informal side, and I would like to steer it to be a little more formal. Toward this end, if I may, I would like to introduce a theory of scientific objects that Historians of Science favor. In part, objects become scientific objects because scientists study them. Supernovae are on the one hand, scientific objects, because scientists attempt to understand how they work and chart their light curves. On the other hand, you are using Supernovae as tools for making distance measurements. Is that a binary? Are those the two ways that you think about Supernovae, having spent years with them, now?
I actually do. My life with Type Ia Supernovae started out with understanding the physics of them: why do they explode, how do they work, how much iron do they produce. The tool, while we like to kid ourselves, as being directly related to that, up to this point it has really just been a tool of convenience. The brain that I use to do that operates via statistics, not physics. We have been trying for the last decade, to use the physics to better understand the tool. It has been something we have spent a lot of time on, to motivate the physics, but it has not necessarily been controlling how we use them as distance indicators. So, yes, we do tend to use them in those two ways.
Has the Supernova as tool influenced Supernova physics at all?
It has energized the number of people and the effort gone into looking at the physics of Type Ia Supernovae.
You are finding so many more now.
We find a lot, but it is also because when you write grant proposals and things, you can tag this discovery onto it and say that we need to understand it better. It is a motivation to do it. In truth, I do not think the two things are that coupled, even today, unfortunately.
They are the two ways? There are not sub-methods of how Supernovae are used? I am now thinking of the phenomenological aspect, the light curve of the Supernovae, the representations of what you see on the one hand, and on the other hand, the internal dynamics of the Supernovae, analyzing the theory of how they work, could those be the two bins in that method of analyzing them?
I am not quite sure of what you are getting at, unfortunately. When we use them for determining distances, ultimately, we use them as these tools where the physics is removed. We have a little bit of an idea of the physical method of what is going on. But it is not the primary motivation. When I try to understand the physics, then I always have the distances in the back of my mind. But really, I am just trying to understand how they work.
The physics of Supernovae is not the primary motivation, but the physicists care about what you are doing, right?
If you meet Mike Turner, he does not give a damn how Supernovae work. He probably would even be willing to say that to you. I do. I am interested in that physics. That is not physics he is interested in. He is interested in the physics of Dark Energy. I am interested in that as well, but not as much as Mike is.
Let us go back to the theme of scientific authorship and your innovative method of collaborative authorship. After you decided on this, you wrote the first paper.
I wrote the paper, and I already had a draft in 1997. Because we had to go and find more Supernovae, finding those Supernovae and dealing with all the issues of data reduction, helping various people and I did help Adam Riess and Peter Garnavich on data reduction, publication was delayed.
How many activities are you engaged in as a scientist: you are engaged in observing, in software development, engaged in data reduction which is also working with software but in another way.
There is software development for finding the Supernovae and then there is software development for getting the numbers out, that you publish as the discovery — the brightness of the Supernovae, but also how you convert those numbers into cosmological measurements. I was doing simulations of what we should see, and all these other things. I was essentially having to write software which backed up everything — I re-analyzed everything that everyone else did, to make sure that I agreed with it.
What is an example of that?
When we were doing the cosmological fits for Peter Garnavich and then later, Adam Riess, we were not planning to do the cosmological constant. It became clear that we had to do that. I had to write software that would fit for the cosmological constant.
Why would you not have planned to do that?
We were not expecting the cosmological constant to be important until we started seeing evidence for it. Normally, you fit the universe just with what we call a ‘q_0 Curve.’ That is the deceleration curve, which can be acceleration. As soon as we started talking about a cosmological constant, it became clear that we had to use a different model. We had to write that. It went from being a one-dimensional fit to a two-dimensional fit. It is not hard now, that we have done it a lot. We had not done it back in 1997. In 1997 it was not something we had thought much about how to do. There were problems. We had parts of that two-dimensional fit that were not allowed. The model was not allowed. How do you deal with that? There were all sorts of subtle questions that Adam, Peter, and I had to grapple with. We had to write all of that software.
The moment when you saw that Lambda would be interesting for this, was that when Adam did his calculation from the data analysis, or was it before or after that?
I was sifting through my notes. Because our first object, 1995K very much showed acceleration, although the uncertainties were such that you could allow deceleration, I realized when I wrote the draft of the paper that I had to deal with the cosmological constant. It looked foolish, expressing the result in any other way. When I was writing that, starting in March of 1997, right after this meeting, I had done that fitting, to move into the cosmological constant. But, I will say, I did not take it seriously. It was just one of those things.
This was also around the time that the Supernova Cosmology Project published their deceleration result.
That is correct. They referred to the cosmological constant in that paper. That was also related to my paper, because I wanted to compare my answer to theirs.
How influential was their deceleration result on your team? Did you see your paper, and say, okay that looks right?
I noticed immediately, that 1995K was very different. It bothered me.
Our 1995K was almost two standard deviations away from their result. I was suspicious, but it was one object and I just did not know. With just one object, you just shrug your shoulders and say, “This will all fix itself.”
What was it about the object that was so different?
My object was almost a factor of two fainter at the same distance, as theirs. Almost a factor of two — which is huge! It was something like 80 percent fainter, plus or minus 30 percent. It was a big difference.
You had not published this yet?
No. It had gone into several telescope proposals. It had been shown at conferences, but it did not get published until 1998.
The other team did not know about it?
They had seen it.
Since they had not obtained it, it did not worry them that much?
I would imagine that it would have, but I honestly do not know. When Adam sent me the first data, which was done well, Peter Garnavich was at the same time working on a Hubble Space Telescope data set. I would say that data was more consistent. You did not have to have a cosmological constant. There were objects that were closer to no deceleration, to a model of an empty universe. That data set, for whatever reason, did not demand the cosmological constant. That was what we were working with in July and August.
Here you were in Australia. Were you still doing observing? How often do you observe?
I had been in Chile in January of 1997. I was in Hawaii in April and May of 1997. Then, we had to go back to Chile in October, November of 1997. It was a lot of time.
Was Adam also doing observing?
He may have gone to KECK on one of the runs to do spectroscopy. Adam never did any of the search runs.
He only did spectra?
He did spectra. The difference is, with spectra, you go there, have a list of things, you look at them, and go home. The Supernova searches were two and a half weeks of pure hell. I cannot describe them as anything else. That was an aspect which the people in Chile will know, and John Tonry will know in Hawaii. Pete Challis knows, at Harvard, and Peter Garnavich did a lot of as wells.
I like these clear answers: there is this kind of telescope run and there is that kind of telescope run. You performed these at different telescopes, mostly?
We needed wide fields, 4 meters and then we needed the biggest telescopes in the world to deal with the spectroscopy.
You did more searching that spectra collecting? You were very concerned with the spectra, because you made those color filters.
The color filters were for the photometry.
For the searching?
Yes. I did a little bit of spectra, but I did not do most of the spectra.
That was done by Adam and Alexei?
I would say, that was done by lots of people. Adam and Alex, yes, but Bruno Leibundgut did a lot. Peter did some. A whole variety of people did it. [Interruption, Schmidt says hello to Maarten Schmidt, who discovered quasars.] The spectroscopy was spread amongst many people. It was the observational side of spectra that Alexei Filippenko particularly took a lead in. Adam did a little bit of it, but he was more the data analysis guy.
He was not necessarily the data analysis guy from the beginning?
No. He would have started in 1997 (in earnest in 1997, a bit of stuff in 1996 as well). He did some simulations. He had a very good way of measuring distances, so I would routinely ask him to do things. He would do them. If you look at the things he did, they were quite sophisticated. He did lots of simulations of what we needed to do. That was especially what he did early on.
Why do you say that the search runs were like hell?
Every single time we got there, the computer systems changed. As I told you yesterday, we had problems with the software not running. I would arrive with my software, which worked fine the last time I was there. I would get it running, and everything would be broken. We would just be frantically trying to get it all to work again. Every year, we had more and more data, and the computers were better and better. But it was always right on the very edge of what we could handle. The other team had a huge advantage because they did all of their analysis largely back in Berkeley on a system that they could keep stable and working. That was a huge advantage. They were very smart about that. I have to admit that I thought they were kind of crazy doing it that way. However, they did it the right way. We did not have the resources to do it their way. Even if we did, it is not clear that we would have. They did it right. That was where their mentality of how they do things in particle physics was better.
The centralization keeps everything fixed and controlled.
What is the problem with making the software work? Is it that the computer systems at the telescopes changed?
The computer system that we do the data analysis on changed. It was a very complex system. We could not just run on one machine. We had to run on nine different machines.
Wow; all at the telescope?
All at the observatory at Cerro Tololo. We had new disks, pieces of software that we were relying on no longer exist we had changes of operating system break software. I would have it all working in Australia, but then I would go to Cerro Tololo and it would break. I would go to Hawaii and it would break. I was doing all these things and our software was barely adequate. It was not great software because I was spending my time doing other things. We were spread very thin.
You were the ‘go-to’ person for the software, and I am sure it is just out of modesty that you are saying it was not great. You were the person who had to handle those problems when they happened.
I had to show up. The software would not work without me being present, period. That was just the way it was. I never really had enough time to fix it.
You would go for two weeks at a time?
I would do two weeks at a time. Ideally, I would then spend three months trying to get it right again, to fix all the problems. I was too busy doing other aspects of the search at that time.
Helping with the data reduction, the analysis, helping write telescope proposals, all those things.
Do you think that you lost a lot of Supernovae because you had to be going back and forth. You still found many!
Yes. We found enough but we were inefficient in finding them, no doubt about it.
Did you ever see a Supernova and then lose it somehow?
No. That was not the issue. Especially in the first year, we just did not have enough Supernovae. In later times, the software was working well enough that we would find probably more than we could handle. Then there were other issues, like filters breaking, it being cloudy. One year it was cloudy in Cerro Tololo on the 1st epoch (these are the images we subtract from the second epoch) and it was mainly cloudy in Hawaii on the second epoch. So we were taking the data from Hawaii and subtracting it from the Cerro Tololo telescope data. That opened up a can of worms. I cannot believe that we even attempted to do it, quite frankly, but we did. It was always something. Nothing ever worked smoothly. Every search run was new.
Despite nothing ever working smoothly, you made the discovery.
We did make the discovery.
Do you think there was a time delay because of this. Do you think that if things had gone smoothly, you would have made the discovery earlier?
No. The only thing it affected was my ability to work as a human being. It completely drained me of all my energy. It kept the 1995 K-paper from coming out earlier that is for sure, because I was too preoccupied to do that. Eventually I started getting heart palpitations, so I stopped. I said, “Okay, that is enough of doing that.”
Oh, no. Well, it involved a lot of traveling, too, going from Australia all over.
It was a terrible trip. It used to be 45 hours, typically. That is a long trip. In the spring of 1997, when we decided who was ‘It’, we all went our different ways. Peter Garnavich had this new data, which we took with the Hubble Space Telescope in Hawaii. Adam Riess had all the old objects. We were not sure who was going to end up going first. I cannot quite remember how it was going to go. What ended up happening was that we decided to do a quick paper on the Hubble data, because we thought we were going to get scooped by the other team. We did not know what the result was, but we did not want them publishing anymore because then we would have ended up without telescope time that we needed. We decided to go for a very quick paper, which Peter would write, and then Adam would write the next, bigger paper, which I quite frankly did not expect to be as interesting as Peter Garnavich’s paper. I had done the calculations and as a result, I thought that Peter’s paper would give you the answer to first order. Adam is a very demanding collaborator. He worked very hard, but he also worked me very hard. He was continually asking questions. Adam always asks questions on the phone. I do not think there is any real email traffic to talk about so much. I do not have it. I do not know if Adam does. He would always call me up and we would work through things. We did that a lot, for several months.
In the fall of 1997?
Summer and autumn on 1997. There was a lot of to-ing and fro-ing. That was the great thing about Adam, is he was so demanding, that he really made me work hard. You might think it would be the other way around, but no. He was really pushing things along.
And this was specifically with you rather than with everyone else in the collaboration, or would the others say the same, do you think?
I do not know. He was certainly trying to get other people to reduce data, but that never went. The idea was to have Adam write up the paper, and have lots of people do a light-curve each. In the end, however, Adam had to do almost all of them himself. I had one to do. I think I actually did mine. Saurabh Jha had one to do. A bunch of people had them to do. He was pretty hard on everyone, but he was, I think, particularly demanding of me. The only thing that saved me, most of the time, was the time zone. [Pavlish laughs at joke.] He was in Berkeley at the time, so it was only five hours. He did wake me up several times in the middle of the night, much to my wife’s disgust.
I was just about to ask about the spaces of collaboration, or interaction, or scientific work. Is it a cliché or incorrect to say that the universe is your laboratory?
The universe is our laboratory, but unfortunately, I think it is my toolbox, I do not get to change things. I just have to be clever about what is there and how to learn about what is around us. It is cliché-ish to say that it is our laboratory, but it is not wrong. It misses a subtlety. We look around and try to figure out how to be clever with what is there around us.
There are these spaces of your work. One of the interesting things is how many there are, both physical and non-physical like talking on the phone. Maybe if we could go through what they are that would be helpful: there is the space at the telescope, or at the observatory.
We call it the observatory, which includes the telescope and where we are doing the data reduction. The people there are talking and working with each other continually.
In a NOVA special, when they show you all at the telescope, is that control room where you control where you control where the telescope points in the sky, the same place where you also do the data reduction or are there different rooms?
Initially we were doing the data reduction up there. Then, finally they got an Internet connection where we could work down where there were more computers. So for a couple years, yes. Later on, no, they were separated.
Is it better that way? Does it change the way you work?
Yes. For example, if one is up observing at Mauna Kea at 13,500 feet, it is almost impossible to do anything sensible. It is just too hard. So, it is important to be separated under those circumstances. When we did the initial data reduction, we would be up at the telescope, running the telescope, and trying to find Supernovae simultaneously. That is distracting and you end up doing both and doing neither particularly well. In one particular run, I accidentally deleted all the data we had taken that night. Fortunately there was a backup automatically made somewhere, and we were saved. For a second, there, I thought that my career had come to an end. This would have been in 1995. Nick Suntzeff realized what had happened. I was thinking, how am I going to tell Nick that I just deleted all the data? There was no recovery as far as I knew. Suddenly, about thirty seconds later, I saw the backup data.
Time is so valuable there at the observatory, time is money.
We had four nights of time. I completely destroyed, or thought I had destroyed a night, and we lost a night to weather. I was worried that we were not going to find any Supernovae, in this, our second run. I thought that it was done. There is the career! There was a moment for about fifteen seconds, when I thought this was it.
When scientists have very expensive laboratory equipment or data, this might be a shared terror.
Yes, and there is just no recovery. That is the problem. It was terrifying.
There is no recovery because the Supernovae are going to be gone.
That is exactly why we quite working up there, to stop errors like that.
When you go to the observatory, do you still go up to direct the telescope?
I did initially, but not in the end.
Do technicians do that?
No. Nick Suntzeff or Bob Schommer. Peter Garnavich did a lot of the observing up in Hawaii, up at the CFHT. John Tonry and I would go down and reduce the data. Peter, after the observing was done, would come down and help as well. In Chile, sometimes I went up to the telescope. As we got longer and longer into it, I did it less and less. I spent more and more time down, finding the Supernovae.
There is that. There are the offices where you work at your home institutions. The offices, like you said, at Cerro Tololo, where you decided to start the collaboration itself. Any other physical spaces where important scientific work or exchange takes place?
Well, we would have these meetings, these collaboration meetings. That was the place where lots of ideas were shared, and we talked over how to proceed in the future.
Were those meetings just with your group? There would also have been workshops or conferences.
No, this was specific to our group.
In Cambridge, MA?
We had one in the basement, in Cambridge.
Yes, down in Perkins, way in the bottom of the building there is a little seminar room at Harvard-Smithsonian Center for Astrophysics that was the first one we had. We used that many times. We had one in an Astronomy room in Hawaii. We had one in the Astronomy Room at The University of Washington, in Seattle. Then, we had effective ones in Chile, where we had three quarters of the collaboration there.
You would take notes there? Was there a secretary?
You would get together for a really intense day?
Yes, for a really intense two or three days; we would work on data, talk about the problems, we would work on software, discuss future proposals and projects, and how we were doing. We tried to do everything at these collaboration meetings, because they were the only times when we could all get together.
Did these feel very horizontal?
Yes, very horizontal.
Or, did you go up to the front of the room and say: okay, the topics of discussion today will be one, two, three.
No. Complete free for all. That was one of the problems with me being the nominal leader. I was not comfortable leading my thesis supervisor and my various mentors around the world, so we sort of led in a collaborative way. I had a rough agenda of what we would do, but the actual topic would be, say, four hours of discussion on one thing, and those four hours would be a free for all.
Do you think that was unique for this kind of work?
I would say that is a very common way for astronomers to work. Would I do it that way today? No. I would be much more organized.
Were they difficult to orchestrate?
Not too much. The local person would more or less take responsibility. We all agreed to show up there, and we would go there and argue. [laughs] Everyone was pretty cranky, under stress.
So there are these spaces, and then there are these non-spaces that are still spaces, like email exchanges, phone conversations, sending software or sending postage stamps of data. Any others like that, sending images or texts?
The email of course covered all media, almost immediately. Attachments did not exist. You would encode something, send the email, and they would un-encode it. They did not know what they had until they un-encoded it. It was always a surprise, and you prayed that it was not something that was going to eat at your computer.
What fraction of your work was of this kind? How much of your work was solitary, how much of it required physical presence of other members of the team, how much of it was looking at the computer screen?
The physical presence was probably only five weeks a year, but I was working twenty hours a day for those five weeks. That is why I got heart palpitations. It almost killed me. There was a lot of effort there. You would sort of go home and be a bit of a basket-case after that.
Is that typical for Astronomy?
No, it is atypical. I think that in the old days people did that a lot. I do not think that it is done so much anymore. Working on the data would be in your office, interrupted by conversations via email. Most of the collaboration was email contact. Adam was unique in the telephone contact. He really liked talking on phones. Saul also likes talking on phones. He hates email. Even to this day, I do not even bother writing Saul emails. I will typically text message his mobile, and say: Call me up.
You do have that sort of frequent interaction with him too?
No, but three or four times a year I need to get his attention, or he needs to get mine.
I think of this as a chunk of what is of interest to historians: how and where you work.
Yes. That is how we work. Mostly, in the office, but we would not work a day without firing off several emails. It was not like work for a week, and then write an email. It was, like: email, email, email, phone call, work, work, work, work, work. Even if only a half hour of a day was spent that way, there was a lot of communication. We were not isolated.
That might be a characteristic of scientific collaborative authorship, that you have this constant interaction.
I think it is new. It was not possible twenty-five years ago.
Electronically. I was talking to a scientist, a graduate student, who said that when he is at work, he just walks down the hall to talk to his advisor several times per day.
I used to that a lot when I was at Harvard. A lot of collaboration, in the past, as soon as it got outside of your group, it was done independently. You would work on a hunk, then compare it to a hunk, then try to bring it together. I would not say that there was much communication. This was like, we were virtually, by electronic means, in the same hall, even though there was probably a six or eight hour delay most of the time.
Were there misunderstandings as a result?
Whenever there are emotive issues, email is a terrible method of communication. When you are not doing science, but rather talking about emotional issues like who gets to author a paper, which is quite a bit in a big collaboration, those led continually to misunderstandings and anger and all sorts of things.
I know that from other spheres also.
It is a terrible means of communicating emotive issues.
This is tape two of the interviews with Professor Brian Schmidt. It is June 25th and we are back at Caltech to continue our interview from yesterday; where we left off continuing our conversation on collaboration.
The only difficulty was if email was not transmitted properly, so if it was corrupted. The time delay could often cause problems. It could delay us by a day.
These are very interesting, these group meetings you had. We did not talk about workshops or conferences where you had to present your data to other teams. That certainly is an opportunity to talk to people from your own group and from other groups. There is the question of how much information to keep to yourself and how much to share.
Right. I showed Supernova 1995K in a meeting in Aigua Blava in Spain, in 1995. It was one object. It was to show progress. Most of the collaboration was there. They got to see the stuff too even though I had already sent it around to everyone. Interestingly enough, our group was almost the entire observational Supernova community. We did not have the Italians on board but we had everyone else who were publishing in that area.
What about the SCP?
The SCP had never done Supernova stuff before. They were not part of that community. They typically did show up at these Supernova conferences because it was not what they did. They did show up in Agua Blava. That was the beginning of when they started showing up at those conferences. There was a meeting in Chile, in February of 1997, which was on Supernova 1987A. I had to give a talk about something not at all to do with cosmology. I had to give it about work that I am also talking about tomorrow, on the other type of Supernovae that I work on. We did not talk too much about cosmology at that conference. I cannot remember all the conferences very well right now.
Would you rank any of these places of interaction as being less or more important to the work. Maybe the group meetings would be most important?
Obviously, the individual discussions by phone and email were absolutely essential to get the work done. Absolutely essential! The meetings were the next cut. We got a lot done, but they were not as essential. I would say that almost nothing happened at the conferences, besides telling other people what you were doing.
Adam showed a photograph of you, him, and Gerson Goldhaber sitting at a table.
Yes, at Agua Blava.
I asked him if you could have been talking about Supernovae there. Could you have exchanged any essential information during that conversation?
I do not think we exchanged any essential information. But, we had a nice talk with Gerson. The two teams were very combative at that time. Not so much, me.
Yes. Kirshner and Filipenko who had switched sides at that point, were not very friendly toward Saul and his group. It was pretty combative. Adam and I went there. It was, I think, Gerson’s way of seeing what we were like and trying to smooth other things. Did we talk any deep science? No.
If one were to include images in a history, would that be an important image or not? There is a limit to what is captured on photograph, but is a nice picture.
It is a nice picture, but I think it illustrates the exception rather than the rule. That photograph shows one of the only times we were ever socially together with members of the other team.
Although Adam played football with Peter Nugent.
He may have. I was not there. He was sort of connected to that group, a little bit.
He said that when you guys were doing the important work he was no longer playing football, or at least not talking about the work.
I do not know. He certainly was very careful about keeping our work secret from them, once it got interesting.
If we could save that time for later, I would like to go through a list of questions I have and see if we find something interesting to talk about. Do you enjoy observing?
I used to. I do not anymore. I do not like staying up late. I love data. But, I try to make it a point to try to automate all of the things I am involved in now. I did enjoy it until the High-z work. It was just too much. It overwhelmed me. It was those 20-hour nights that sucked any enjoyment out of it, out of me.
Do you think there is a difference between visualizing a scientific object or process, and producing or consuming a visualization? Say, between how you imagine a Supernova explosion to be, or the accelerating universe in your mind, and how you represent these findings to other scientists or to the public?
No, I think they are the same. I try to visualize the science in the same intuitive way that I explain it to other scientists and even the public. I figure that my mind probably works like most people’s and so I find it is very helpful to use the same intuitive visualization that I have.
Peter Gallison has a paper in which he describes how Dirac was famous for being very mathematical, not at all pictorial in his communication. But, Galison found some pictures that Dirac drew for himself to understand the science better. He was visualizing the science in pictures for himself, but whenever he presented it, it was always mathematical.
Maybe it is the difference between a theorist and an observer, but I am very into figures. Given a choice, I always like figures and diagrams to explain complex things, and it is the same picture that I have in my mind.
Do you produce those figures for yourself, to come to conclusions? Or, do you have the conclusion already and only then make the figures?
Occasionally, for complex visualizations, I will do the figure for my own benefit. Usually I do it mentally. That is one of things I do in the shower: I visualize what is going on. Then, when I write the paper or give a talk, I convert that visualization in my mind into a slide for the audience.
You carry it around in your head beforehand?
Typically. Occasionally I will sketch something out, if it is too complex to keep in my mind. Then, I have to draw it out and sift through how it works. I try to break things down into very simple pictures.
I have seen a DVD about the discovery, produced by a major news organization for Chinese television. For the documentary, the TV crews visited your home and office in Australia. I thought I saw a portrait of you in your office. You like pictures for the purpose of science. May I ask, if it is not too personal: are you also an artist yourself?
No. That picture in my office was painted by my sister-in-law and was entered into an art competition in Australia called the Archibald prize. You can paint politicians, scholars, and artists. Since I am a scholar, I am an obvious target. It is an interesting picture and I do not know what to do with it, so it remains in my office. It is one of those things I am kind of uncomfortable with. Since it has been in my office for seven or eight years, I am used to it there now. So no, I am not an artist myself.
Do you have any documents that you recommend I look after? Adam Riess already shared much from your team.
Adam has shown you a lot of stuff that I already had on the team Wiki. I am trying to think of what would be useful. He showed you our first proposal. I could show you our first 1995K data if that would be useful to you.
I am embarrassed to say that I do not have a copy of your 1995K paper. Is that in the Astronomical Journal or the Astrophysical Journal?
That was in the Astrophysical Journal. I do not know what Adam sent and did not send to you. It is all on our Wiki, which is not open. I do not think there is any problem with historians looking at it, but I would have to get twenty people to agree to it, which is not worth it.
Oh, no. I meant documents related to your work, only.
There are some interesting things like the dates when I switched over to putting Lambda in that paper, in September. I can send you abstracts from the Wiki.
Great. This is jumping ahead, but I want to be sure not to leave it out. Let us black box the announcement and your paper. But, after that there was a straw poll at the University of Chicago when approximately fifty percent of the attendees expressed confidence in your discovery, by a show of hands. Were you there?
I am interested in how the discovery became accepted.
I think that Mike Turner was onto this before it happened. Mike Turner was always full of ideas. In 1996 he wrote a paper saying that the cosmological constant is back. Nobody paid any attention to the paper. But he did write it. When he saw ours and Saul’s data, he immediately said that this has got to be right. Mike is a very colorful and powerful figure. He pushed really hard. I would say that rightfully so, people were skeptical. Then, came the first cosmic microwave data that were showing the fact that the universe looked flat.
This was before WMAP?
Yes, this was Boomerang, and Maxima. That would have been in May or June, of 2000, when those came out. The data was highly convincing although it was not perfect… As soon as we saw that the universe was flat from those experiments, I felt much better. As soon as we knew that the Universe was flat, if it only had normal matter in it, our measurement of the accelerating universe went from being 99 percent confident to 99.999 percent confident. That is, we were so far away from that model if there was no cosmological constant.
Wait a minute. I am not clear on this. First of all, the distinction between 99 percent and 99.999 percent is irrelevant to me. Also, it has been found that the matter in the universe is not all ordinary matter.
The difference is that statistically, when you do an experiment, 99 percent confidence sounds good but it is not overwhelming. If you have underestimated your systematic errors a little bit, then you could be wrong. Our result was relatively strong. I was willing to bet my hamster but maybe not even not my dog on it.
This was at the submission of your March paper?
That is correct.
You were willing to bet your hamster that what?
That the universe was accelerating. That was because our data were in the accelerating part of the diagram. Now, what were the alternative models? The alternative models were one, that the universe was slowing down very slowly and made of normal matter or two, that our the universe was flat, made of normal matter, and slowing down very quickly. Our data were completely contrary to the model that the universe was slowing down very quickly and made of normal matter and flat.
So you would have been willing to bet much that it was not flat, like your house?
Yes, we would have had to be grossly incompetent to have done it that wrong.
So it is two separate things to say that you discovered the accelerating expansion and that you discovered that it is not decelerating? If one were to say that this is a discovery, or a process of discovery, it is not the process of discovering one thing. It is more like the discovery that it is not ‘normal matter and flat and decelerating quickly.’
We discovered the accelerating universe. As I said, we were 99 percent sure it was right. An accelerating universe sort of implies Dark Energy under any simple or not even that simple view of the universe. That is what we announced. But it was the cosmic microwave background coming in that sort of said to Joe Blow on the street that these things are so far apart, unless there is Dark Energy, that I have a choice: I either say that there is something horrible wrong or that these two are consistent.
The accelerating universe is dark energy to you now? I looked back to the 1998 Science Magazine Discovery of the Year articles and they do not yet use the term Dark Energy.
Right. It had not really been coined yet. They did use the cosmological constant. Truth be said, Dark Energy to me then, was the cosmological constant.
You were not thinking of it as Dark Energy but it was the same concept?
No. I was thinking of it as Dark Energy but we tagged it as the cosmological constant because that was the simple way to describe it. It was something that people in the community knew about. It was something that astronomers knew about.
Sorry to be sticky about the linguistics, but you tagged it as a cosmological constant but were thinking of it in your team as Dark Energy?
Yes, because we already knew about Quintessence, which was an alternative. Peter Garnavich’s paper, which came out immediately after Adam’s, looked at that. That is, I think, a very good paper because it still looks like a paper we would write today. It is a very modern approach. We had Craig Hogan on our team, who taught me Cosmology as an undergraduate at The University of Arizona before he moved to the University of Washington. He provided a connection to that world that we otherwise would not have.
What world — The quintessence world?
To the particle physics world, so we had that person on our team, to provide a framework where we were not completely at sea.
Now, what would you be willing to bet?
Oh, I do not things have changed that much. At this point, I am pretty sure, but you know it is a crazy world and there could be some conspiracy of errors. Who knows? We just do not know.
Maybe it is not even fair to use that scale. What is important is that this particular method with Supernovae as distance indicators exists and yields that result. There is this scientific context.
Yes. It seems to be the way the world is. I am as sure about it as I am about anything else in science, or at least most things in cosmology. Am I sure that the Big Bang happened? Yes, I am pretty sure. Some people are not.
I saw on the airplane over here that there is a new TV show starting in the fall called ‘The Big Bang Theory’ which in part tries to popularize Cosmology for a young audience.
It has not made it to Australia yet, so I do not know about it, but that sounds interesting. I do not see science as being absolute. There are a lot of things that I think are probably correct but one can never be positive. Do I think that Dark Energy is as strong as inflation? I am actually surer of Dark Energy than I am of inflation. That may not be true of most theorists, but that would be my view at this point.
How about something like the theoretical background you are working with, General Relativity?
I do not know if the acceleration we see is caused by a failure in General Relativity or if it is Dark Energy. My sense is that it is Dark Energy. However, if God came down and told me it was absolutely not Dark Energy, then I would say that well, I guess General Relativity has a problem. That is how sure I am.
A related question is, Einstein commented that one side of his field equation is like a structure made half of marble, that being the geometric side, and the other half of cheap wood, that being the physical part balancing the geometric. What do you think of this characterization? That is where the cosmological constant enters; it is added on one side?
One can add it on either side. That is the problem. It turns out that one can add it to the geometric side so that it is a part of the fabric of space, a constant of the geometry. Or one can put it into what they call the stress energy tensor where it is this thing that is built up and can be moved around. That is the Dark Energy interpretation. It can go either way. I would not even want to comment on Einstein’s views of his equations because I am afraid that my intuition of General Relativity is poor to say the least.
Einstein’s intuition was poor too, perhaps.
When he started, maybe, but it was better than mine.
Maybe we should end here to give you at least ten minutes before the next talk.
It is July 25, 2007. We are continuing our interviews, with this the third tape. Professor Brian Schmidt has been generous with his time, even though he is attending a conference here at Caltech. First, Professor Schmidt, we have this internal document, a story that Adam Riess wrote up about the process of the discovery and announcement of the accelerating universe. He says that it was very much an advantage for the High-z Supernova Search Team that you had a large low-redshift sample.
That is certainly true. We had the large low redshift sample. That added extra precision in our measurement. That was something that had not been published yet, that we could use against the Supernova Cosmology Project’s larger sample at higher redshift. The SCP were using the same low-redshift sample we were, but we had extra objects, as I said, that had not been published because Adam had just reduced them as part of his PhD thesis. The Chilean data, which we used as well, is what the SCP used. That is the data from people on our team.
This is a bit of an ignorant question, but is there a difference between the Cerro-Tololo and Calan-Tololo?
Calan-Tololo is a project. Cerro-Tololo is the actual observatory, which is the Tololo half of the Calan-Tololo collaboration. The Calan-Tololo data set was taken by Mario Hamuy and Jose Maza and the guys at Cerro-Tololo in the early 1990s to get this good data set. The University of Chile and Jose Maza worked together to get to get this good data set of Type Ia Supernovae.
That was a side question. It definitely was an advantage to have those low-z Supernovae?
It was an advantage in that it gave us some additional signal. It was not a huge advantage, but it was an advantage.
He discusses using Omega_Lambda as a free parameter. I remember in our earlier discussion, you talked about Lambda as a parameter.
That is the same thing; it is just my shorthand.
This was in the fall and winter of 1997?
I started using Omega_Lambda as a free parameter in March or April of 1997 but only because I had to do something with my object. I became very serious about it with Adam’s data set.
Did you recommend to him to do that?
I was definitely doing it. I think he knew he had to do it. When he first showed me the data he had not done anything yet. He just showed the q_0 curves and they were all above. That is my memory. Then, it was very obvious what needed to be done. The fact that I had already done it earlier did not affect things much — I did not need to say anything.
It was intuitive what you all had to do?
Here, I listed seven ways in which you come up in this story. We have already discussed your “IT” innovation. Your photometry software package is what we discussed, as you shuttling back and forth between Australia and Chile?
The photometry software reduction package was a tool-kit I used to actually convert the found Supernovae into objects we could publish, into data we could publish.
That is separate from the observing software?
Yes. That was a tool-kit we used. Both Adam Riess and Saurabh Jha used it in their thesis, and I used it as well. That is why it was developed.
How many software packages did you write?
It was an ensemble of things that I bundled up in different directions. I cannot really describe it. Lots, Lots and lots of lines of code.
Is that described here?
The actual codes are not described but the basic process that we did, is. There is the search software and then we had the data reduction techniques.
The photometry tool-kit is part of the data reduction techniques?
Yes. There are all sorts of things. There are K-corrections. There are all these things that I did, then Adam re-did and then other people re-did again. It was all done several times, which is good. That is how you know that you are doing things right.
But you were the programmer?
Different people wrote different programs. I did most of the data reduction stuff.
I am sorry that my questions about the software cannot be astute, because I myself have not done that sort of thing. I have only done a bit of lab-work, so that I can relate too.
When you re-measured the relative photometry, did you happen to be at an observatory where you could do that?
No. What we did, is that I took the data that Adam had measured with my data reduction package, and I re-measured it. What he does not know is that I re-measured several other ones without telling him. [Pavlish laughs] I did to want to offend him but I did not completely trust him. [laughs]
Somewhere, perhaps in Professor Kirshner’s book, I read that you named the Supernovae?
Saul’s group started doing that first. That came later. We thought that was a good idea later on, but that was all after 1998.
So, 1996-H or something, is not going to have a fun name.
Then, he quotes your email, ‘Hello Lambda’ of January eight.
I think at the end of November, the first stuff came through where it was very clear that the data was saying: Accelerating Universe.
He sent this to you?
He sent it to me only as an email that said, “What do you think of this?” That is all that it said, and it just had one figure on it. I do not have a copy of that email, and Adam does not have copies of things he sent, he only has things he received, I believe, so this is vague recollection. I do not know the date that that happened, but I believe that it was right at the end of November, that is my memory. We started talking about checking, and doing things, and I remember through December, going through lots of little things, again and again and again, to deal with this. One of the things we had to deal with, that I was really struggling with, was how to do our error analysis. We had bits and pieces of the diagram, which we knew we were not allowed to go into. [birds chirping outside]
On the Hubble diagram?
No, this is where you do Omega_Matter versus Omega_Lambda and try to measure both of those simultaneously. There are parts of that diagram that you are not allowed to go into. We were struggling with how to do that statistically. As I said, I was trying to reproduce his results for a lot of December. On January eight we finally agreed about everything. But there was about a month of stuff done there, when we were reproducing each other’s results.
This is the part of the plot you are referring to? [shows diagram]
The problem was, we were trying to figure out how to deal with the fact that the contours extend here but that is not allowed.
That would yield a negative mass.
Yes, exactly. That was the difficulty. We were struggling. We tried different ways to do it. This [example you show] is the formalism that we eventually adopted, but it took us a while to get there.
That is equation ten in the Riess et al paper of 1998.
Yes. That was Adam’s doing. It was not mine. It took us a little while to get there.
It was the two of you going back and forth on email?
I think that Peter Garnavich was involved in these because he was trying do the stuff for his paper at the same time. Yes, it was email and phone calls.
I was wondering how many of you were in on the secret. Maybe, Alexei Filippenko would have known about it also?
Alexei Filippenko would have known about it, I assume.
Anybody else in the group?
I do not believe so. I do not even think that Peter even knew about it. We kept it very quiet. Frankly, I was not sure at all that I believed it initially and I did not want to get people excited too early, mainly because we would lose confidence within the group. Within the group, we had had some very, very heartfelt wrenching of how to do the experiment in September. [“You’re always working,” one of the organizers of the conference walks by and says to Schmidt. “This is an interview, no worries,” Schmidt answers, laughing.]
Earlier on our way to the interview, we were talking and a journalistic question is, how well can we pinpoint the discovery?
Certainly, January eight, Australian time, which would have been January seventh, US time, is when Adam and my analysis agreed. I should not say that that is when my analysis agreed with Adam’s. That is when Adam and I concluded that we agreed on the analysis, exactly. There were several little disagreements along the way, with some him and some my being right and wrong. When we agreed, on January eight that happened to be the day of the AAS conference. That email was sent the morning of the AAS conference. I was in Australia, but the conference was on the eight. That is when we agreed. Was that the discovery date? No, but that was the date when I said we had to tell people.
Tell people within the group?
Yes. I think Peter Garnavich [who was presenting at the AAS meeting] already knew at this point but I do not think most of the other people in the group knew. This is a place where judgment is key; is a tough one to say exactly.
Here it says in Adam’s story that you were writing a description of the parameters of the Supernova search in the spring of 1996.
I started writing this paper in 1995. However, it was always the bottom thing in my stack to do and so it dragged on and on and on.
Do you think there was an advantage in publishing it later?
No, it would have been better earlier. It would have been really good to have our 1995K out there for everyone. I would not have been a major advantage, but it would have been good for me to have gotten it out, rather than continually laboring at it. When we submitted this, December 1997 is just a blur to me. I do not remember anything, but working day and night. I have to admit, I probably did not even think of the irony of the title of my paper [Deceleration, rather than Acceleration in the title, when the result was Acceleration]. That title had been with the paper for three years. I did not even think about that, despite knowing that the universe is accelerating and one piece of this paper, had that data in it as well. It was realized that this was a funny title. But, what is the generic term? We decided that the generic term was deceleration, because we think in terms of mathematics where the sign is what determines whether the result is deceleration or acceleration. We had always thought it would be deceleration. As I said, in that last month, I may or may not have realized the irony. I do not even remember. It was certainly the least of my worries at this point.
Had you ever mused about acceleration before the data came in?
Yes, once. When I was in Boston, I was with a friend of mine who is a biologist at Harvard. We were talking. She was saying, “What are you working on?” I described the beginnings of this experiment. She said, “Wow, that sounds big. You know, you could win the Nobel Prize.” I said, “Oh, yeah right. Only if there is a Cosmological constant.” That is what I said at the time. It comes off so bad now, but it is a true statement. That is a true thing that I said, at the time. In retrospect, I guess it is not that big of a deal. That is the one time when I mused about acceleration. [*** logically connected below] The other time, I refereed a paper by Goobar and Perlmutter, looking at the cosmological constant, which was submitted in 1995. They made their simulations assuming that there was no Cosmological constant. It turns out that the limits to the cosmological constant if there were no cosmological constant, and the universe was low matter, were not that interesting. They were there but they were not that interesting. It is only if there is a cosmological constant that you get interesting observations on it. Imagine if you take an error ellipse and you put it right here, you could still have a huge Cosmological constant. I was the referee of the paper, and I said it is fine but it is not very interesting. They did not particularly complain about it. The reason was, if you move these uncertainties you can still have a cosmological constant of one. It does not make any difference. Those were the only musings I had about a cosmological constant. I did not worry about it otherwise. [this is connected logically to the *** I put above] As I said, it is an uncomfortable thing. I did have the conversation, but I literally laughed afterwards. I thought that it was not going to happen. The world was not going to be that crazy that there would be a cosmological constant. That was a flippant comment because it seemed so preposterous to me.
One of the people I interview, his advisor, Rabi, had a Nobel prize and the advisor’s advisees would plan on getting the Nobel prize.
I do not think that Nobel prizes are good to plan on, I am afraid.
Here, I perceive a change. In the sixth item you email the group that it is in the best interest of the team to publish quickly. Next, in another email after that, you say that the paper should include the data, data reduction, search procedures, collaboration measurements, error budget descriptions, conclusions, and decisions. And then you say, your decision that a longer paper is a good idea and should only take an extra week or so.
I said we needed to do a quick thing because at this point we had seen Saul Perlmutter’s data. Although he had not fully interpreted it as being absolutely acceleration, I knew what our data said. He did not know we had the same result. He was worried about extinction, about dust. We had corrected for dust from the day one. When I submitted this paper, I believed that Perlmutter et al were still getting Omega_Matter equals one. Eight days later, I found out that their Supernovae are faint, just like ours. I knew that we had corrected for dust. We were ready to go. There was a real imperative to move quickly. I never said I wanted to do a quick and dirty paper. I think I said we must go fast but complete. The data must be on there. I am pretty sure that is what I said from the start. There were ideas of putting this in Nature. I said, “Over my dead body.” I was anti-doing-that.
To what extent does the Riess et al paper stand alone or not stand alone from the other papers from your group. There were four papers by members of your group in 1998. Then, there are papers from before and after. I will talk a bit here to set a conceptual tone for the following discussion. Bias can be introduced by the historian either by the sources that one analyses, or by the questions that one asks. For example, if I am interested in visualization, scientific objects, how experiments end? Then, how about how experiments begin?
We spent a lot of time on that obviously, yes.
Right. What about that? This paper, Schmidt et al, is about how the experiment is conducted.
Yes, we laid out the base of it. Adam’s paper is the hard core analysis. A lot of the details, the boring details are in my paper. Those are the fundamental details of how we did the experiment. Adam’s paper is how we then analyzed the data. It has some of the details repeated in here. Then, it provides the result and test of why believe the result is correct. It is a pretty comprehensive paper. I would say that the papers do go together as the team’s effort. Peter Garnavich’s paper is less comprehensive than this because we were not trying to do anything too fancy in it. We had laid out the basics in my paper. Things had changed a bit. Consequently this is a more comprehensive paper than the first Garnavich paper. The next Garnavich paper is actually quite innovative because it is the first one to look at the equation of state, which is talking about the Dark Energy. My paper talked about how to do that because of Craig Hogan. I thought he was crazy, when he started telling me in 1995 that I had to worry about this. I have to admit that I was not so sure, initially. It turned out to be quite good. We had the entire idea of the equation of state in here already. That was several years ahead of the game.
Can the historian ask how this experiment ends?
This experiment has not ended yet. I say that because although the High-z team disbanded in 2003 that is when we did our last paper by Tonry et al, we morphed into Adam’s led Higher-z program with The Hubble Space Telescope which I am not a part of, and the Essence program which is led by Chris Stubbs. It is still the same players trying to do the same thing. It is a little bit of a restructuring, but the experiment goes on. The reason is because Supernovae are still the best way, right now, to quantify dark energy. We do not understand what it is yet. That is why it continues on. I personally am right on the edge of being ready to end the experiment for me. Whether or not other people in the group will end it is unclear. But, I probably am ready for it to end. I am ready to look at things in different ways or change the composition. I think things need to be shaken up.
You get complacent. It is the same people. You do not expand your mind. You do things the same way. You become very insular. That is bad. That is the problem.
Maybe not the end of the experiment, but when is it that everyone in the group agrees on the result or when does the result gain general acceptance in the scientific community?
The group was certainly suspicious. I think that we were worried. It is not that people in the group said, “This is wrong.” There was just this intuition, that the result cannot be right. We could not find anything wrong with the experiment. I think that when we submitted in March, we were there. Anyone who did not want to be on it could pull his name off the paper. I think that everyone agreed that they were happy that Adam had done a great job on this paper. The rest of us had gone through everything we could think of. It gained acceptance. The worry was that we had forgotten something somewhere. Who knows. The general acceptance by me and the general community I think happened when there was this other data. There was this Cosmic Microwave Background data coming in that I told you about. That got me most of the way. WMAP coming in and the 2DF redshift survey coming in. Everything then went together. At that point it came almost undeniable. By the year 2000 I felt pretty good. I was definitely worried in 1998. When it became Science magazine breakthrough of the year of 1998, I was horrified. I did not know it was coming. It certainly surprised me.
Another quick aside, I would like to extend what we discussed about scientific visualization in our last interview. Is it something like this diagram that you are visualizing off the page?
Typically, the best visualizations are kept for talks. In my paper, in figure four, I want to give the idea of how bright an object is as a function of redshift. That gives people who are astronomers an immediate idea of how easy our experiment it is. I wanted to show the process here in figure five of how we went from figure one, which is a large version of a postage stamp, the 30th of March, a new object. The Supernova is kind of hard to see, it does not just leap out at you. And then, boom, you subtract and it does leap out at you. That is what I was trying to show there, the whole process.
To do these, you need the machine with you.
I had my computer.
But you cannot make figures like this in the shower.
No, but on the other hand I knew what I wanted to show in the shower. I could picture, “I want that, that, and that.” How we do light curves. One of the big innovations that nobody had done before was John Tonry’s idea. People had always shown these diagrams which John calls White space diagrams. There is no information in them at all. His idea was to subtract off the empty universe model and then one can really see what is going on.
Those are figures 10 and 11 in the paper. Did you start doing that earlier or is this the first example of that type of figure?
I was in Hawaii in 1997 doing a Supernova search. He said, “Why don’t you do this?” I did it, and it stuck. Everyone started to do it immediately. It was a very clever way to do it. That was John Tonry’s idea. When I give public talks I really try to lead people through the idea with figures.
I have your Shaw prize talk here. I think what might be best is if I show you these questions and ask you to skim them quickly, and decide to answer some.
Who can absolutely not be left out of the story of the discovery Dark Energy? Myself. Adam Riess, obviously. Peter Garnavich was absolutely essential. Nick Suntzeff and all the guys in Chile who really founded that bit. Alex Filippenko was involved as a real stir all the time. Pete Challis, who is not a PhD person but an RA with Bob Kirshner, has busted his butt forever. There are really no slouchers on our team. I kept on referring to Craig Hogan, as having a real outlook guidance. Chriss Stubbs, providing a physicsy, experimental program, having those ideas. Bruno Leibundgut had done a lot of work, was always a good friend, and was always a moderating force for a lot of the spectroscopy. Jason Spyromilio is also at the same institution with him. Chris Stubbs’ students like David Riess who worked on the programs, and Al Dircks helped with the search. Everyone on our team was involved. I do not even want to go into the other team because I do not know. I will let them figure that out. It is my belief that there were no slouchers on our team. Other people do not necessarily agree with me but they did not get to see what everyone did, like I did. I really was at the center of the experiment and could see all sides of it. Did I discuss the result with anyone else other than my colleagues? With my family? I must have discussed it with my wife, but I do not remember the details.
What were your responses from non-scientists? They probably just said, “Wow.”
When I give public talks I get all sorts of philosophy questions, which sometimes drift off into never-never land and other times I sort of know what they are talking about. That is a tough question. My family accepts the result, I guess. I try to explain it to them as best as I can. Maybe they are too close to it. They have seen it forever. In my opinion, when do experiments or observations really end or come to their conclusion? I think I have said, that when you think that you have answered the question. We have made a discovery but we have not answered the question. That is why we have not ended.
How big or small of a question are you answering?
We answered a question but we opened up such a bigger question. We set out to ask a big question, in my opinion. But then, we opened up an even bigger one. Consequently, we have not felt like we could end yet because we could use the same experiment to learn more.
Wonderful. That is a nice answer.
How do we go from images to numbers? We take pictures, which are actually quite beautiful. One of my favorite parts of astronomy, which unfortunately is probably not true of most people, is that I love the science that comes out of them. Science is not looking at beautiful pictures. It is transforming those electrons that we have detected into how bright an object was, very precisely, at the other side of the universe. That process of turning that image into that number is very elaborate. It is something that Astronomers have been learning how to do for decades. I learned my skill down at Cerro Tololo, visiting those guys. They were some of the world’s best experts at it. We typically call that photometry. Photometry is the key of this experiment: being able to take those electrons, in the form of a digital camera image and converting it into precise physical measurements.
That is with CCDs?
Right, CCDs, which are the same thing as what is in a digital camera, typically. It is just fancier versions of that. It is easy to do to a factor of two but if you want to do it to 1 or 2 percent that is quite challenging.
What do you mean by a factor of two?
If I want to know how bright a star is, it is easy to get the brightness to a factor of two. It is even easy to get it to 10 percent. But we wanted to get it to 1 or 2 percent and that is a challenging thing to do.
Was the reason you needed such accuracy because the star is embedded in a galaxy?
Yes, but it is also because the experiment needed to be accurate to better than 15 percent. There were lots of places to go wrong. You certainly do not want to mess up on something that is challenging but possible, and completely within your own ability to control. There were a lot of things that we could not control in this experiment, but this was our experimental setup and we could minimize the problems there. Was I involved in naming Individual Supernovae? We started that process, I think, in 1999. We started with cartoon characters. Yes, I was responsible for the Scooby Doo characters. I was into Scooby Doo when I was three or four. The next year, we did dinosaurs, which I hated, but I was overridden by the group. I named the first one. The Chileans were the ones who wanted to do dinosaurs. I found a Chilean dinosaur called a Pisonasaurous, which I thought was well named. That was the first one of that year. How does the resurrection of a discarded concept change our view of the universe? I think it shows the scientific process. We always think of science as being rigid and right. You have a theory. The sociology of people outside of science is that ‘science is right.’ It is not evolving, constantly changing. Science is right or it’s wrong. I think this shows how science really does evolves. You have ideas, but they fade away because they do not make sense. Then, suddenly you get new data and suddenly they make sense again. Or, it may be that we get new data and our current interpretation disappears as well. It would not surprise me, because that is I think how science works.
For some of us that would be pretty depressing.
John Updike has a book called Toward the End of Time, and he integrated the Big Crunch in there. Then, he found out about this discovery, he read about it in The New York Times and he was depressed. There is the one depression, which I cannot relate to, which they also write about, a depression because of an accelerating universe that becomes dark and cold and lonely. The other kind is when one becomes dedicated to a paradigm and it turns out to be wrong.
The acceleration idea could disappear, but that would get rid of General Relativity as well, so we are all going to be depressed. But, the whole idea of it being Dark Energy has a bigger chance of going away. Maybe it is extra dimensions. Instead of saying that the universe is full of Dark Energy, we might say that it looks like it is full of Dark Energy but actually there are nine dimensions and one of them is curled up into a ball and interacting with another one, and that is causing this. That would be an interesting change. I do not necessarily say that that is what is going on, but something like that could occur. It would be great because that would mean we would understand.
So, if it is accompanied by greater understanding then the change should not be depressing.
Chaos is bad. We do not want to be wobbling around with no new knowledge. That is really bad, I agree. That is depressing for everyone. We always want to learn more, we do not want to say that we do not understand anything. Sometimes that it true, but it is not a happy thing when that happens. How has dark energy transformed our understanding of the universe? Borrowing a quote from Adam, “You only get to discover 70% of the universe once.” It is true. We have discovered 70% of the universe. That is the simple explanation. You only get to do that once and we do not know what it means yet. We now know, because of this discovery, that the atoms you and I are made of are 4% of everything. We are a tiny tip of the iceberg of what is going on in our universe. From a philosophical point of view, that is pretty profound. Whether or not it is going to overturn our understanding of physical laws is to be determined, but I think it has the potential to do so. I think that Dark Energy is the most dominant thing in the universe, is pretty amazing to me and amazing to be a part of. Was this a discovery in the conventional sense? I think it is. I think very rarely do discoveries come as eureka. They are long and thought out, like a particle discovery at CERN. You go through, you see that maybe there is something there. Then, you keep on working on it, working on it, working on it. Then, voila, you finally say that yes, that is it. Occasionally, when they get a new instrument, they open it up and see something new right away, because the instrument is so much more sensitive. I think those are pretty rare. I think that when you have an idea of the discovery, you think, wow, and then you have a month or two when you have to come to terms with it, I think that has got be typical. I have only made this one discovery, but I cannot believe that it is not typical. If you look at the history of the Gruber prize there have been a lot of truly amazing astronomers who received it, who have truly done singular things by themselves. This is not that. There is no one on our team, and no one on the other team, who is one of these absolute iconic members of astronomy. It is the strength of the team that led to the result. Lots of people are fairly good astronomers, but there is no Jim Peebles in our group. We added up and were able to do something great. That is one of the neat things. You can add up and do great things if you work together. That, to me, is truly impressive. It is probably true of a lot of teams, but some of the leaders of the teams always tended to be bigger than life. Rubbia is always going to be that person. You will know better how that works than I do.
Like, the Alvarez of a particle physics group.
We do not have any one icon. We should not have an icon. If anyone is considered iconic that would be wrong. That the way it really works. It is possible to work together constructively, do good things. As I would say, I would love to have the whole team benefit. I am afraid, if you look at our team, almost the entire team is active in astronomy still. That is not true of the other team. Together, we can do good things. I think that is paramount. There is more than one way to skin a cat. If you are a cat, I am sorry. Saul’s group’s method was very different from our method. We managed to get there at about the same time.
By method, do you mean ‘scientific method’ or do you mean ‘collaborative method’?
Well, by method I mean the way we approached the project from a management point of view was very different. The whole history of the two teams was different. The scientific method was pretty similar in the end but arrived at by quite different means by the two teams. Is there one other thing you wanted to ask?
I have been thinking about these key words for the historian, which I found in your writings, like evidence, method. For a historian they are good words. You even touched on that right now.
We knew what we wanted to do. We really did set this up as an experiment where we would do A, B, C, and D, and then we would get our answer. That is what this Schmidt et al paper sets out. We were always looking for a technique, which was expected to provide well-defined measurement which we could defend; I guess that would be our evidence. Then, in this Riess et al paper, of course, we found evidence. We always used the word evidence. We never said, “It is a discovery.” For us, it was, “This is the evidence. This is the simplest conclusion we could come to. Let us see what people think.” I think we use the word discovery now because it is accepted but at the time we would have definitely not used it.