Personal

George Field, brilliant theoretical astrophysicist and truly great human being, passed away on the morning of July 31. He was my Ph.D. thesis advisor and one of my favorite people in the world. I often tell my own students that the two most important people in your life who you will (consensually) choose are your spouse and your Ph.D. advisor. With George, I got incredibly lucky.

I am not the person to recount George’s many accomplishments as a scientist and a scientific citizen. He was a much more mainstream astrophysicist than I ever was, doing foundational work on the physics of the interstellar and intergalactic medium, astrophysical magnetic fields, star formation, thermal instability, accretion disks, and more. One of my favorite pieces of work he did was establishing that you could use spectral lines of hydrogen to determine the temperature of an ambient cosmic radiation field. This was before the discovery of the Cosmic Microwave Background, although George’s method became a popular way of measuring the CMB temperature once it was discovered. (George once told me that he had practically proven that there must be an anisotropic microwave radiation component in the universe, using this kind of reasoning — but his thesis advisor told him it was too speculative, so he never published it.)

At the height of his scientific career, as a professor at Berkeley, along came a unique opportunity: the Harvard College Observatory and the Smithsonian Astrophysical Observatory were considering merging into a single unit, and they needed a visionary leader to be the first director. After some negotiations, George became the founding director of the Harvard-Smithsonian Center for Astrophysics in 1973. He guided it to great success before stepping down a decade later. During those years he focused more on developing CfA and being a leader in astronomy than on doing research, including leading an influential Decadal Survey in Astronomy for the National Academy of Sciences (the “Field Report”). He never stopped advocating for good science, including in 2016 helping to draft an open letter in support of climate research.

I remember in 1989, when I was still a beginning grad student, hearing that George had just been elected to the National Academy of Sciences. I congratulated him, and he smiled and graciously thanked me. Talking to one of the other local scientists, they expressed surprise that he hadn’t been elected long before, which did indeed seem strange to me. Eventually I learned that he had been elected long before — but turned it down. That is extremely rare, and I wondered why. George explained that it had been a combination of him thinking the Academy hadn’t taken a strong enough stance against the Vietnam War, and that they wouldn’t let in a friend of his for personality reasons rather than scientific ones. By 1989 those reasons had become moot, so he was happy to accept.

It was complete luck that I ended up with George as my advisor. I was interested in particle physics and gravity, which is really physics more than astronomy, but the Harvard physics department didn’t accept me, while the astronomy department did. Sadly Harvard didn’t have any professors working on those topics, but I was randomly assigned to George as one of the few members of the theory group. Particle physics was not his expertise, but he had noticed that it was becoming important to cosmology, so thought it would be good to learn about it a bit. In typical fashion, he attended a summer school in particle physics as a student — not something most famous senior scientists tend to do. At the school he heard lectures by MIT theorist Roman Jackiw, who at the time was thinking about gravity and electromagnetism in 2+1 spacetime dimensions. This is noticeably different than the 3+1 dimensions in which we actually live — a tiny detail that modern particle theorists have learned to look past, but one that rubbed George’s astrophysicist heart the wrong way. So George wondered whether you could do similar things as in Roman’s theory, but in the real world. Roman said no, because that would violate Lorentz invariance — there would be a preferred frame of reference. Between the two of them they eventually thought to ask, so what if that were actually true? That’s where I arrived on the scene, with very little knowledge but a good amount of enthusiasm and willingness to learn. Eventually we wrote “Limits on a Lorentz- and Parity-Violating Modification of Electrodynamics,” which spelled out the theoretical basis of the idea and also suggested experimental tests, most effectively the prediction of cosmic birefringence (a rotation of the plane of polarization of photons traveling through the universe).

Both George and I were a little dubious that violating Lorentz invariance was the way to make a serious contribution to particle physics. To our surprise, the paper turned out to be quite influential. In retrospect, we had shown how to do something interesting: violate Lorentz invariance by coupling to a field with a Lorentz-violating expectation value in a gauge-invariant way. There turn out to be many other ways to do that, and correspondingly many experimental tests to be investigated. And later I realized that a time-evolving dark energy field could do the same thing — and now there is an ongoing program to search for such an effect. There’s a lesson there: wild ideas are well worth investigating if they can be directly tied to experimental constraints.

Despite being assigned to each other somewhat arbitrarily, George and I hit it off right away (or at least once I stopped being intimidated). He was unmatched in both his pure delight at learning new things about the universe, and his absolute integrity in doing science the right way. Although he was not an expert in quantum field theory or general relativity, he wanted to know more about them, and we learned together. But simply by being an example of what a scientist should be, I learned far more from him. (He once co-taught a cosmology course with Terry Walker, and one day came to class more bedraggled than usual. Terry later explained to us that George had been looking into how to derive the spectrum of the cosmic microwave background, was unsatisfied with the usual treatment, and stayed up all night re-doing it himself.)

I was also blessed to become George’s personal friend, as well as getting to know his wonderful wife Susan. I would visit them while they were vacationing, and George would have been perfectly happy to talk about science the entire time, but Susan kept us all more grounded. He also had hidden talents. I remember once taking a small rowboat into a lake, but it was extremely windy. Being the younger person (George must have been in his 70s at the time), I gallantly volunteered to do the rowing. But the wind was more persistent than I was, and after a few minutes I began to despair of making much headway. George gently suggested that he give it a try, and bip-bip-bip just like that we were in the middle of the lake. Turns out he had rowed for a crew team as an undergraduate at MIT, and never lost his skills.

George remained passionate about science to the very end, even as his health began to noticeably fail. For the last couple of years we worked hard to finish a paper on axions and cosmic magnetic fields. (The current version is a bit muddled, I need to get our updated version onto the arxiv.) It breaks my heart that we won’t be able to write any more papers together. A tremendous loss.

• AIP Oral History Interview — July 1980, part 1
• AIP Oral History Interview — July 1980, part 2
• AIP Oral History Interview — December 2007
• Autobiographical Essay — “Wondering About Things”

As far as I remember, the first time I stepped onto a university campus was in junior high school, when I visited Johns Hopkins for an awards ceremony for the Study of Mathematically Precocious Youth. (I grew up in an environment that didn’t involve spending a lot of time on college campuses, generally speaking.) The SMPY is a longitudinal study that looks for kids who do well on standardized math tests, encourages them to take the SATs at a very young age, and follows the progress of those who do really well. I scored as “pretty precocious” but “not precocious enough to be worth following up.” Can’t really argue. My award was a slim volume on analytic geometry, which — well, the thought was nice.

But the campus made an impression. It was elegant and evocative in a way that was new to me and thoroughly compelling. Grand architecture, buildings stuffed with books and laboratories, broad green commons criss-crossed by students and professors talking about ideas. (I presumed that was what they were talking about). Magical. I was already committed to the aspiration that I would go to university, get a Ph.D., and become a theoretical physicist, although I had very little specific concept of what that entailed. Soaking in the campus atmosphere redoubled my conviction that this was the right path for me.

So it is pretty special to me to announce that I am going to become a professor at Hopkins. This summer Jennifer and I will move from Los Angeles to Baltimore, and I will take up a position as Homewood Professor of Natural Philosophy. (She will continue writing about science and culture at Ars Technica, which she can do from any geographic location.)

The title requires some explanation. Homewood Professors are a special category at Hopkins. There aren’t many of them. Some are traditional academics like famous cosmologist Joseph Silk; others are not traditional academics, like former Senator Barbara Mikulski, musician Thomas Dolby, or former UK Poet Laureate Andrew Motion. The official documentation states that a Homewood Professor should be “a person of high scholarly, professional, or artistic distinction whose appointment brings luster to the University.” (You see why I waited to announce until my appointment was completely official, so nobody could write in objecting that I don’t qualify. Too late!)

It’s a real, permanent faculty job — teaching, students, grant proposals, the whole nine yards. Homewood Professors are not tenured, but in some sense it’s better — the position floats freely above any specific department lines, so administrative/committee obligations are minimized. (They told me they could think about a tenure process if I insisted. Part of me wanted to, for purely symbolic reasons. But once all the ins and outs were explained, I decided not to bother.)

In practice, my time will be split between the Department of Physics and Astronomy and the Department of Philosophy. I will have offices in both places, and teach roughly one course/year in each department. The current plan is for me to teach two classes this fall: a first-year seminar on the Physics of Democracy, and an upper-level seminar on Topics in the Philosophy of Physics. (The latter will probably touch on the arrow of time, philosophy of cosmology, and the foundations of quantum mechanics, but all is subject to change.) And of course I’ll be supervising grad students and eventually hiring postdocs in both departments — let me know if you’re interested in applying!

You’ll note that both departments have recently been named after William Miller. That’s because Bill Miller, who was a graduate student in philosophy at Hopkins and became a successful investment banker, has made generous donations both to philosophy and to physics. (He’s also donated to, and served as board chair for, the Santa Fe Institute, where I will continue to be Fractal Faculty — our interests have considerable overlap!) Both departments are already very high-quality; physics and astronomy includes friends and colleagues like Adam Riess, Marc Kamionkowski, and David Kaplan, not to mention benefitting from association with the Space Telescope Science Institute. But these gifts will allow us to grow in substantial ways, which makes for a very exciting time.

One benefit of being a Homewood Professor is that you get to choose what you will be designated a professor “of.” I asked that it be Natural Philosophy, harkening back to the days before science and philosophy split into distinct disciplines. (Resisted the temptation to go with a Latin version.) This is what makes this opportunity so special. I’ve always been interdisciplinary, between physics and philosophy and other things, and also always had an interest in reaching out to wider audiences. But there was inevitably tension with what I was supposed to be doing as a theoretical physicist and cosmologist. My predilections don’t fit comfortably with the academic insistence on putting everyone into a silo and encouraging them to stay there.

Now, for the first time in my life, all that stuff I want to do will be my job, rather than merely tolerated. (Or not tolerated, as the case may be.) The folks at JHU want me to build connections between different departments, and they very much want me to both keep up with the academic work, and with the podcasts and books and all that. Since that’s exactly what I want to do myself, it’s a uniquely good fit.

I’ve had a great time at Caltech, and have nothing bad to say about it. I have enormous fondness for my colleagues and especially for the many brilliant students and postdocs who I’ve been privileged to interact with along the way. But a new adventure awaits, and I can’t wait to dive in. I have a long list of ideas I want to pursue in cosmology, quantum mechanics, complexity, statistical mechanics, emergence, information, democracy, origin of life, and elsewhere. Maybe we’ll start up a seminar series in Complexity and Emergence that brings different people together. Maybe it will grow into a Center of some kind. Maybe I’ll write academic papers on moral philosophy! Who knows? It’s all allowed. Can’t ask for more than that.

People often suggest guests to appear on Mindscape — which I very much appreciate! Several of my best conversations were with people I had never heard of before they were effectively suggested by someone. Suggestions could be made here (in comments below), or on the subreddit, or on Twitter or anywhere else.

My policy is not to comment on individual suggestions, but it might be useful for me to lay out what I look for in potential Mindscape guests. Hopefully this will help people make suggestions, and lead to the discovery of some gems I would have otherwise overlooked.

• Obviously I’m looking for smart people with interesting ideas. Most episodes are idea-centered, rather than “let’s talk to this fascinating person,” although there are exceptions.
• I’m more interested in people doing original idea-creation, rather than commentators/journalists/pundits (or fellow podcasters!). Again, there are always exceptions — nobody can complain when I talk to Carl Zimmer about inheritance — but that’s the tendency.
• Hot-button topical/political issues are an interesting case. I’m not averse to them, but I want to focus on the eternal big-picture concerns at the bottom of them, rather than on momentary ephemera. Relatedly, I’m mostly interested in talking with intellectuals and analysts, not advocates or salespeople or working politicians.
• I’m happy to talk with big names everyone has heard of, but am equally interested in lesser-known folks who have something really interesting to say.
• Sometimes it should be clear that I’m already quite aware of the existence of a person, so suggesting them doesn’t add much value. Nobody needed to tell me to ask Roger Penrose or Dan Dennett on the show.
• I like to keep things diverse along many different axes, most especially area of intellectual inquiry. Obviously there is more physics than on most people’s podcasts, but there will rarely if ever be two physics episodes in a row, or even two in the same month. Likewise, if I do one episode on a less-frequent topic, I’m unlikely to do another one on the same topic right away. (“That episode on the semiotics of opera was fine, but you need to invite the real expert on the semiotics of opera…”) More generally, podcast episodes should be of standalone interest, not responses to previous podcast episodes.
• I am very happy to talk with people I disagree with, but only if I think there is something to be learned from their perspective. I want to engage with the best arguments against my positions, not just with any old arguments. Zero interest in debating or debunking on the podcast. If I invite someone on, I will challenge them where I think necessary, but my main goal is to let them put forward their case as clearly as possible.
• Corollary: someone is not worth engaging with merely because they make claims that would be extremely important if they were true. There has to be some reason to believe, in the minds of some number of reasonable people, that they could actually be true. My goal is not to clean up all the bad ideas on the internet.
• Obvious but often-overlooked consideration: the person should be good on podcasts! This is a tricky thing. Clearly they should be articulate and engaging in an audio-only format. But also there’s an art to giving answers that are long enough to be substantive, short enough to allow for give-and-take. Conversation is a skill. (Though Fyodor Urnov barely let me get a word in edgewise, and he was great and everyone loved him, so maybe I should take the hint.)
• This is a long list, but the most useful guest suggestions include not just a person’s name, but some indication that they satisfy the above criteria. A brief mention of the ideas they have and evidence that they’d be a good guest is extremely helpful.
• None of these rules is absolute! I’m always happy to deviate a little if I think there is a worthwhile special case.

Thanks again for listening, and for all the suggestions. I am continually amazed at the high quality of guests who have joined me, and at the wonderful support from the Mindscape audience.

For anyone who hasn’t been following along on other social media, the big news is that I’ve started a podcast, called Mindscape. It’s still young, but early returns are promising!

I won’t be posting each new episode here; the podcast has a “blog” of its own, and episodes and associated show notes will be published there. You can subscribe by RSS as usual, or there is also an email list you can sign up for. For podcast aficionados, Mindscape should be available wherever finer podcasts are served, including iTunes, Google Play, Stitcher, Spotify, and so on.

As explained at the welcome post, the format will be fairly conventional: me talking to smart people about interesting ideas. It won’t be all, or even primarily, about physics; much of my personal motivation is to get the opportunity to talk about all sorts of other interesting things. I’m expecting there will be occasional solo episodes that just have me rambling on about one thing or another.

We’ve already had a bunch of cool guests, check these out:

• Social psychologist Carol Tavris
• Theoretical physicist Carlo Rovelli
• Historian/activist Alice Dreger
• Atheist theology professor Anthony Pinn
• Complexity theorist Geoffrey West
• Professional poker player Liv Boeree

And there are more exciting episodes on the way. Enjoy, and spread the word!