Historian of physics Alexander Blum.
Photo by Amac Garbe / Max Planck Society.
From 2017 to early 2025, historian of physics Alex Blum led the Final Theory research group , which was jointly hosted by the Max Planck Institute for the History of Science (MPIWG) in Berlin and the Max Planck Institute for Gravitational Physics in Potsdam. The group’s work was focused on the various efforts by physicists to develop a unified framework encompassing all known physical phenomena.
The winding down of the group this year represents the end of an era for the MPIWG, which has been an important global center for work in the history of physics since its establishment in 1994. That work was led principally by Jürgen Renn, the institute’s founding director. After he completed his long tenure in 2023, the MPIWG began a pivot toward other subjects.
To better understand the value of such programs for the history of physics, we asked Blum some questions over email about the Final Theory group’s research, how it operated, and how it might set an example for future efforts.
Will Thomas: How did the Final Theory group get started at MPIWG, and what were its main goals?
Alex Blum: The Final Theory group (full name: Historical Epistemology of the Final Theory Program) was a Max Planck Research Group. Max Planck Research Groups are time-limited collaborative research projects, led by a mid-career PI. The Max Planck Society acts as the funding organization, while the individual Max Planck Institutes act as host institutions.
Normally, only one of the society’s 84 institutes (with topics ranging from art history to molecular biomedicine) acts as host for a given research group. But in the mid-2010s, Max Planck president Martin Stratmann initiated a new type of research group, hosted by two institutes with different research foci, aimed at fostering interdisciplinary research and collaboration within the Max Planck Society. The Final Theory group got started in the context of this program and was hosted by the Max Planck Institute for the History of Science in Berlin and by the Max Planck Institute for Gravitational Physics (also known as the Albert Einstein Institute) in nearby Potsdam.
The group’s objective was to study the history of the search for a final theory—a central theme of 20th-century physics, from Einstein’s search for a unified field theory to modern-day quantum gravity and string theory. That isn’t really all that interdisciplinary: our research questions genuinely belonged to the history of science, even though we got a lot of emails and calls from people who thought we were actually looking for a final theory ourselves.
But our work did connect the history of science with physics in two main ways. One, since it was so closely connected to unsolved problems and currently ongoing research in physics (quantum gravity was a central research topic at the Albert Einstein Institute), physicists were a main audience for our work—in particular young researchers trying to situate their own research in a greater historical context or looking for inspiration from the open questions of the past.
Two, in order to read and understand our historical sources—letters, published papers, notebooks—we actually had to work through the calculations performed there and thus engage in work not unlike that of a theoretical physicist. This kind of deep engagement with the scientific content has become quite rare in academic history of science, so, from the vantage point of that discipline, our work did look interdisciplinary.
Thomas: About how many researchers took part in the group, and (recognizing the impossibility of encapsulating everyone’s work) can you offer a few highlights or representative examples?
Blum: The group ran for a total of seven years, which unfortunately included the entire COVID pandemic. In this period, the group hosted a total of eight postdocs and six graduate students, as well as numerous visitors, with stays ranging from three days to three months.
I think that together we’ve crafted a new narrative framework for the history of the search for a final theory. This history actually begins before relativity and quantum mechanics, the great revolutions of the early 20th century. It has its origins in the electromagnetic worldview of the late 19th century, when many physicists were hoping to reduce all of physics to (and replace Newtonian mechanics by) the configurations and dynamics of the electromagnetic field (or rather of the ether).
That program was severely set back by the revolutions of modern physics: relativity famously killed the ether, and quantum theory first gave rise to a new mechanics, with field theory taking a back seat for the time being. Einstein certainly felt cheated out of the dreams of his youth, and he continued to pursue the ideal of a unified field theory, now including the gravitational field—but, as everyone knows, not quantum mechanics. Indeed, we can understand Einstein’s disappointment with quantum mechanics better when we realize how opposed it was to his unificatory vision.
Einstein’s program was far removed from the mainstream, of course, and from the 1930s to the 1970s the ideal of a final theory did not hold much currency. A constant influx of experimental results—beginning with the discovery of new particles in the 1930s to the particle zoo of the large postwar accelerators—enabled a pragmatic, phenomenological approach to physics that eschewed grand visions. Also, quantum field theory, the most natural language for a final theory, struggled with foundational difficulties throughout this entire period.
Steven Weinberg speaks at an American Physical Society press conference at the New York Hilton Hotel in 1966. Weinberg was a key figure in the establishment of the Standard Model. He published the popular book Dreams of a Final Theory in 1992.
Photograph by Mitchell Valentine, courtesy of AIP Emilio Segrè Visual Archives, Physics Today Collection.
Only in the 1970s, with the establishment of the Standard Model of particle physics on the basis of quantum field theory, did physicists return to the search for a final theory, though they had difficulties transferring the pragmatic methods and concepts of particle physics to this more foundational endeavor. We see the results of this tension in the debates on string theory in the 21st century.
The 1970s also saw the rise of alternative, non-reductionist ideas in physics, but while concepts such as emergence worked well in critiquing the possibly naive notion of a theory of everything, physicists ultimately did not manage to find a new, non-reductionist vision that could serve to ground the unity of physics as a discipline.
That, in broad brushstrokes, is the framework that we’ve established in numerous papers and books, and that the alumni of the group will hopefully continue to flesh out in their new academic homes.
Thomas: How well did this work as a collaborative project? Do you have ideas about how historians can do this kind of work in the future?
Blum: I think by the standards of the history of science it worked very well as a collaborative project. One mustn’t forget that single authorship remains the standard in academic history to this day, so it was necessary for each researcher to pursue their own individual projects on which to build their career. But, just like in physics proper, the complexity of the arguments and calculations—as well as the discovery of serendipitous interconnections—often led to or even necessitated collaborative work, including a paper with a whopping (for history) four authors on the paradoxically foundational role that approximations played in postwar high-energy physics.
More importantly, I think that working together in close proximity and closely related topics led to a shared vision of what history of physics can achieve when it is pursued with dedication and attention to all of its aspects, and I hope that vision will endure. Generally, the importance of the history of the exact sciences within history of science as a discipline is decreasing—at least it feels that way from my vantage point in Berlin. But I hope that new, maybe more permanent, centers will pop up in the future.
There certainly is an uptick in historically minded philosophy of physics in Europe, with a number of ERC-funded research groups, including one by Final Theory group alumnus Sébastien Rivat. We’ll see what will happen within academic history of science itself. And I also hope that physics departments and institutions will step up (like the Albert Einstein Institute did in hosting our group). If they do, I think they will come to appreciate the synergy between research, historical reflection, and outreach.
William Thomas
American Institute of Physics
wthomas@aip.org
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