Josie Enenstein: Can you please share about your background?
Dr. Mark Trodden: I am originally from the UK. I did my undergraduate degree in Mathematics at Cambridge University. At the next stage I did a Masters Degree in Math at Cambridge where I specialized in theoretical physics. Then I took a year and did research there with a professor and during that year I started working with one of her collaborators who was in the US at Brown University. After that year, I applied to graduate school and I got accepted to Brown and went there to work with this person. I did my Ph.D. at Brown. And then I was a post-doctoral research associate at MIT. And then I was a senior post-doctoral research associate at Case Western Reserve University. And then in 2000, I became an Associate Professor at Syracuse University. I was a professor there through 2008. And then I moved to Penn where I am now. I went there as a professor and to start the Center for Particle Cosmology at Penn.
JE: What did of research were you doing while you were at Cambridge?
MT: I was already working on problems that you might call particle cosmology. There is an interesting question in cosmology of where do the big magnetic fields in galaxies come from? The general feeling is that they start off as small magnetic fields and they grow through something called the cosmic dynamo. And the question is then where do those small magnetic fields come from? One possible view is that they are cosmological in origin. They are not true to the galaxy itself. They come from something else. We work on our other exotic idea to do with something called cosmic strings which are these very exotic things that happen in particle field physics theories. We were interested in whether the fact that they can carry currents could allow them to generate magnetic fields. That was the very first paper I ever wrote. It was a long time ago now, and it was with a professor, Anne Davis at Cambridge, who was really in some ways responsible for starting my career, and also with the person who eventually became my Ph.D. advisor, Robert Brandenberger.
JE: When you made the move to come over to Brown, was it that same project that inspired you to come over here?
MT: Actually, it is a much more boring story than that. When I was at Cambridge, I had a girlfriend, and she was American. So, I said maybe I will go to the US to study my Ph.D. By the time I went to the US and studied for my Ph.D., that was all over. That’s what opened my eyes to the possibility of studying for a Ph.D. Indeed, working on this project with these two people was the sort of thing that drove me to go to Brown and apply to Brown and work with this person. He was great, and it was clear to me that he was incredibly smart but would also be a great mentor. He really cared about his students.
Although when I got to graduate school, we worked on slightly different things. There I started being interested in the question of why there’s more matter than antimatter in the universe. Laws of physics at some level seem to treat matter and antimatter the same way. And yet, everywhere around us, in fact out to the limits of the observable universe, the universe appears to be made of matter, not antimatter, for the most part. This is a big problem in cosmology. Part of my Ph.D. thesis was to try to come up with some interesting way of addressing that problem, again using these exotic particle physics solutions that are called cosmic strings. To try to use those to generate this asymmetry in the universe.
JE: Were you doing similar work as a post-doc at MIT or Case Western?
MT: Similar only in the sense that it was particle cosmology. My interests are quite broad, meaning sometimes I work on pure particle theory, sometimes I work on things that are more dealing with cosmology. Often, I am right in the middle. If you are smart, you typically don't pursue the same things for all the rest of your career that you did in your Ph.D. The field moves on and you're supposed to be one of the people driving it ultimately. I have continued to do bits of work here or there on that topic of the matter antimatter asymmetry. But for the most part, as a post-doc, I became interested in the role that super-symmetry can play as the exotic symmetry of nature in particle theories and for cosmology. In particular, I became very interested later in the question of initially why the kinds of cosmological models that can emerge if there are more dimensions than the three we observe in the universe. And that was a very good time, an explosive period in that idea. There were lots of new ideas out there and we contributed to that.
But around the time that I was beginning my second post-doc, that was when people discovered that the universe was really accelerating. I have worked on a lot of different things since then. That has been a consistent part of what I have worked on for much of the last 15-16 years. That’s the area to which I moved.
JE: Are there any important milestones you can remember where technology has been able to evolve and how that has changed the research going on?
MT: The big effect of technology in my field is…see, I am a theorist, so for the exact kind of work I do, the biggest change is computers. Computers have changed out of all recognition. Sometimes people think computers are useful in theoretical physics for simulating systems. You don’t know what a bunch of particles does, because it’s complicated. You put their rules on a computer, and watch what they do. You solve the equations numerically. And that’s true. A huge amount of that goes on. The whole discovery of gravitational waves that has happened in the last few years would have been impossible without the tremendous advances in computer power and computer algorithms to model the systems.
But there’s a whole other part of this that people don’t talk about very much which is there’s a lot of very powerful software packages now that are used not to simulate systems, but to manipulate the equations in a way that you imagine the classical picture of a mathematician or theoretical physicist sitting in front of a piece of paper writing symbols and working out formulae – and I do a lot of that – but a lot of that, the really complicated stuff you can automate with a computer. And that has become in many ways a tool of great convenience, enables you to do things quickly, and for some problems, a tool of absolute necessity. There are problems that without that you would not be able to solve. And in theory, that’s the big advance, computers for those two applications.
In experiments, which I don’t do but it is very important in my field, there are more advances than I could possibly list, but certainly the microelectronic revolution and the way in which….The technology in your cell phone camera, the charge couple devices that allow you to have a little camera in you cell phone, CCDs, those writ large are the basis of most of the large survey telescopes that we build these days. When I say “we” I don’t build them, other people do. That technology has come a long way. There are many other examples like that.
JE: Do you have a favorite project on which you have worked?
MT: It is very hard to answer questions like that. An easy answer to give would be, this question of the accelerating universe. There’s a whole class of approaches to explaining that which would come under the rubric of modified gravity. One class of those approaches, we invented. We wrote a seminal paper in that area. Our paper has been cited a ridiculous number of times. It is quite famous. So, in some sense, it would be rather easy to give that as the answer. That is definitely the thing of mine that has gotten the most attention by other people. But it is not the thing I enjoyed doing the most.
The thing I have enjoyed doing the most…there are a number of them and they are usually papers that are quite mathematical and they are usually to do with some sort of technical problem in a theory that I really wanted to understand for me, and I couldn’t understand it, and we eventually figured it out that made me very happy. They are not these explosive papers that everyone pays attention to, but I really loved working on them. They are big in that they solve something technical, but they are very gratifying and you feel coming away from it that what was a complete puzzle to you, a complete black box, and suddenly you understand exactly how it works, and it’s a great feeling.
When I think about projects I particularly enjoy doing, I work almost always in collaborations with others. I really enjoy it. We have fantastic particularly young people to work with in our group. What governs whether a project is great to work on are the people that work on the project. I have been very fortunate to have some fantastic graduate students, post-docs working with me. When that works right, that makes the project become exciting and enjoyable.
JE: What is it like for you to be the head of a department at a big university?
MT: I have a rule that I don’t complain about that. It is a large amount of work. It is very interesting in the sense that there are skills you have to develop that you don’t necessarily have when you start the job. It is not like being a boss. No one is below you. You don’t get to order people around. We are a very democratic system, but you do get to guide the way in which the department works. At its best, it is very exciting in the sense that you get to argue passionately for new hires in the department to the administration. And if you do that well, make the arguments to be compelling enough, sometimes you get those positions and then you get to hire get people into the department. And I have been fortunate to do that six times or so since I have been chair. And it’s just been great. We’ve hired wonderful people.
At its worst, bad things happen in a department occasionally and you have to deal with it. You have to sort it out. You have to deal with the people involved. Sometimes there are very delicate things to deal with. Things that are confidential. People have difficulties. People have health problems. You can’t solve those problems for them, but you are usually the person who has to help them navigate how to deal with that in the context of the department. And sometimes that’s really difficult.
My term is up in July [of 2019] and I hope to be able to look back and think that I did some really good things for the department and learned a bunch of new skills. I’d like to be able to look back in 10-20 years at how the department looks and say I played a role in making the department that way. In that sense, it’s a really nice thing to have done.
JE: When you were a child or teenager, was there anything in particular that inspired you to be interested in physics, astronomy or space in general?
MT: I think people like to have an epiphany, an origin story – I was thinking of things and I had this realization this is what I want to do. I don’t have that really. I would say I was a smart kid. My parents were insistent I get a good education. I enjoyed school and I did well at lots of things. I think I realized the thing I enjoyed most at that time was mathematics. So, I went to university to study mathematics. In the UK, that’s what you do. You don’t go to university to study things and eventually concentrate in something. You apply to university to do a subject and that’s what you do when you get there. So, I did mathematics for three years as an undergraduate. At that point, I explained how I went into theoretical physics…as a smart kid, I was always interested in lots of things. And one of the things I was interested in was space and science. I wouldn’t say that was my driving force beyond languages, literature and anything else. The system in the UK is a little different. You study up to 16 where you take nine subjects. And then you specialize for a few years where you do your A-levels. There you do three or four things. There I had to make a decision what to study for those two years. There I had to choose and I chose science. So, I studied math, physics, chemistry and some advanced mathematics subjects as well. So, there I had made some sort of decision. But I didn’t know at the time which of those things would turn out to be the thing that I really wanted. I think by that, those two years of study, I knew that chemistry, while great, wasn’t what I wanted to do. I liked physics, but physics in high school, it can be unfair to say this, was a little mundane. You’re throwing balls in the air, connecting resistors together…But math was sort of exciting. So, I got driven in that direction. Later, through math I got to do the really cool physics. Physics is a cumulative subject. It is very hard to understand general relativity if they don’t understand particle mechanics, when you throw a ball in the air. You have to learn that stuff.
JE: Throughout high school, did you participate in clubs or have internships?
MT: Before college, not at all. When I was going through university in the United Kingdom, those things were not very common. Internships were not common at all. I was lucky enough to get sponsored when I did my degree. I was covered by the government to go to university. They paid my tuition and gave me a stipend. I got some extra money by being sponsored by the ministry of defense of the UK. I worked for them for eight weeks in each of the three summers. That was interesting. The work did not feed into my own work at all, but it was an interesting perspective on what the things I was learning could be applied to. I got to meet some interesting people and work in a place would probably never work later. I got to sign the official secrets acts several times and not tell people what I was working on.
JE: Do you have any advice for somebody who has aspirations of working in that field?
MT: Everyone will have advice for you. Don't be super rigid about what you want you to work on. If you go to university to study physics because you want to do physics, at the undergraduate level, don’t be too hung up on, for example, I want to be a theoretical astrophysicist. Physics is vast. There are huge parts of it you just don’t know anything about before you go to college. And some of it is really amazing stuff.
Biophysics is an amazing area. I have a colleague who just solved the problem of how a squid’s eye works. That sounds like biology. But it’s not. It’s definitely physics. The squid’s eye is a weird thing. No one understood how a squid’s eye works. Now they do. It’s the interplay between biology and soft condensed matter physics. It involves entropy. It’s fascinating. It really takes a physicist to solve that problem. And that’s just an example, and they are many other areas where you might not have thought there’s fascinating physics under it.
First, be open-minded and explore around. Secondly, take the good hard courses. Learn some math. Take the courses you’re advised to take. Tell your advisor you want to go to graduate school in physics. If they advise you to take some courses, take those courses, even if they seem hard. Even if everyone tells you that’s a really hard course. Just commit yourself to doing it and working hard. Grad schools will care that you took the hard courses, even if shaved half a letter grade because it was hard and did not get straight A’s in courses that would have been much easier.
After that, in going to grad school, find a place that will give you options. Find a place that where you think there’s an advisor in the field you think you are interested in, who has a reputation for being good with grad students. If you apply to grad school and get into a bunch of them, go visit all their visiting days and ask the students what it is like to be there, what kind of environment it is, and what the advisors are like in the areas you’re interested in. I can’t overstate how important that is. Particularly as a woman in the science. We are going to underrepresent in physics I particular. I’d like to say the culture is changing and I think it is. But it is not changing super-fast. You work to work in an environment where you can thrive, to turn into that scientist you want to be.