When Alex Blum was growing up in the Black Forest region of Germany, he was consumed by what some might consider an unusual pastime: reading fantasy books and trying to reconstruct the implicit histories of the characters in detail. In the 11th grade, his attention shifted when he was introduced to physics—an interest that would later converge with his passion for history and define his career path.
"I did not know what was going on at all," says Blum, remembering his first physics exam. "Then I had this realization that all they're asking us to do is to put numbers into equations. And that opened up the magical mystery of the mathematical representation of the world to me."
The enigma of physics pushed Blum to study both physics and philosophy at Leipzig University, Michigan State University, and the Technical University of Munich. In 2009, he earned a PhD in theoretical particle physics from the Max Planck Institute for Nuclear Physics in Heidelberg. He then retrained as a historian at the Max Planck Institute for the History of Science in Berlin, where he investigated the search for a final theory of physics. Now, Blum has joined the Caltech faculty as professor of history with a focus on 20th-century physics.
We recently spoke with Blum about his transition from physicist to historian and his focus on modern physics (and a side project focused on listening to all the top albums in the history of popular music).
What inspired your move from theoretical particle physics to the history of the field?
I did my PhD in theoretical particle physics, and I enjoyed the math of it, but I had a hard time believing that what I was doing was going to be confirmed or have some kind of direct connection to the natural world. I took a year off after my PhD and realized that although I still had very many questions, I wanted to think about physics rather than doing it.
I had a long-standing interest in history more generally, not necessarily the history of science, but just history as a process of reconstructing stories from facts. I applied to a project on the history of quantum mechanics at the Max Planck Institute in Berlin, and then I stayed there for 16 years.
How did you decide to focus on the modern history of physics?
That was not necessarily the plan; I was figuring I would branch out and learn interesting stuff about science from the 18th century to today, maybe look at what Isaac Newton was doing. But then I realized that with the skillset that I had acquired as a physicist, I could really engage with the history of 20th-century science in detailed ways that many of my colleagues could not. I had the skills to read the sources in detail and calculate through them to understand what the narrative is and what people are actually doing, and how that contrasts with what they're saying that they're doing; there's always a big gap there.
On the one hand, I saw there was a niche for me to go into. That was the pragmatic aspect. I also felt that I could keep on thinking about the questions that had originally brought me into physics as a youth, especially that question of the mathematical representation of the world and why it's so successful even when it's not perfect. And I had the opportunity to think about these questions from a different, even better vantage point.
What does your research process look like?
When I have a theme I'm interested in, I start with looking at the vast published literature. Because so many papers are published and people cite one another, I try to establish who the relevant people are and how are they related intellectually. Once I've got a map of what's happened on the published record and a list of people who are very relevant, I track down archival sources. Usually, I'm not dealing with super prominent people like Einstein, with source material available in university archives. I have to go treasure-hunting—tracking down relatives to find out whether they still have boxes in the attic or something.
Once that material is assembled, I create a bare-bones chronology. I try to relate the ideas, see when ideas may have circulated before they were published, and how they relate to one another. There's a lot of calculating—a form of translating texts into an argument that you can write about. And then, in the end, the finished product is a story that will also contain detailed mathematical arguments if they're important to understanding what's happening.
Why did you decide to move across the globe to join the Caltech faculty?
I work a lot collaboratively. For example, I've collaborated with a solar physicist on the history of studying the magnetic field of the Sun and with philosophers reflecting on science—maybe in a somewhat different way than historians do. I'm always juggling at least three or four such projects by email. I'm definitely looking forward to that at Caltech; I've heard about the collaboration and communication that the campus and the small size of the faculty enables.
The history of physics that I do engages in detail with the formal mathematics and the conceptual issues of physics. It is not really in the mainstream. Caltech has a small dedicated group for the history of science that is focused on the complicated details of modern and exact natural sciences. And that kind of history is also relevant to the young scientists being trained at Caltech. They don't just hear stories about what the scientists were doing in the olden days. They can talk with the experts about the details of that science and how ideas about nature and its mathematical representation have changed with time. For me, it's the perfect place.
Is there a central focus to your studies?
The overarching research question that I'm interested in pursuing is what do we do once the physics equations that we're trying to solve become too complicated for us to actually solve? People are trying out lots of complicated approximation methods, and there are ideas about somehow transcending this simple equation-solving and moving into a new era of physics where we embrace complexity wholeheartedly. The old cliche of, Oh, I'm a theoretical physicist, I just use pencil and paper, stops working as early as the 1950s.
What will you be teaching this year?
I'm going to be teaching two courses to start. One is a first-year class on the history of the atomic bomb. The most striking thing about that story is that we go from the discovery of nuclear fission in 1939—which was a purely curiosity-driven experiment—to, in just six years, the development of a weapon that changed world history forever. Then, I am teaching an advanced class on how old and traditional ideas are radically changed and uprooted by new experimental discoveries and theoretical developments, tracking how a scientific revolution works in detail.
What do you like to do in your free time?
I like to be outside with my family. I have two sons, and when we came for the recruitment visit in February, Berlin was a frozen-over hellscape; here, we went to the beach and biked and roller skated. Apart from that, I have the very generic pastimes of reading, playing board games with my children, and listening to music. With music, I have an ongoing project, made possible by modern streaming services: I am listening through the entire history of popular music in gory detail. I'm now in the year 1983. I manage about three years per year. I read the Wikipedia article for every album. To me, it's like this sprawling novel of the second half of the 20th century, where all the cultural and societal and political developments intertwine.