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Historically Speaking:
The Bulletin of the Historical Society
November 2003

Volume V, Number 2

EINSTEIN'S CLOCKS, POINCARÉ'S MAPS
AN INTERVIEW WITH PETER GALISON, PART I
Conducted by Donald A. Yerxa

Albert Einstein has become an icon of 20th-century science; indeed, he may well stand as the symbol for the entire century. How do historians explain the importance of pivotal breakthroughs of a theoretical nature—like Einstein’s work on relativity— that seemingly change how we view the world? Are these theoretical advances essentially the product of the genius and creativity of heroic individuals? Certainly it is an article of historical faith that context matters. But how much? In the case of Einstein, for instance, does his work in the Bern patent office have anything more than coincidental bearing on his thinking about time and space? Peter Galison’s latest book, Einstein’s Clocks, Poincaré’s Maps (Norton, 2003), explores these themes insightfully and in illuminating detail. Galison, the Mallinckrodt Professor for the History of Science and of Physics at Harvard University, argues that paying attention to the material context of the worlds that Einstein and Poincaré inhabited deepens our appreciation for their significant theoretical work. Donald Yerxa interviewed Galison in his Harvard office on September 29, 2003. We provide the interview in two installments, the first focusing on the particulars of Einstein’s Clocks, Poincaré’s Maps; the second on how historians of science account for how science has worked in the past.

Donald Yerxa: What prompted you to write Einstein’s Clocks, Poincaré’s Maps? 

Peter Galison: For many years I have been captivated by the question of how abstract issues in theoretical science connect to concrete circumstances—machines, laboratories, instruments. I am fascinated by the way people bring ideas into contact with the physical and completely material world. Einstein, for instance, spent some of his formative scientific years working in the patent office—six days a week, ten to twelve hours a day. And yet during this period he wrote some of the most important scientific papers of his day in quantum mechanics, relativity, and atomic theory. Were these connected? Was it just a day job that Einstein had? In a broader sense, beyond the purely biographical, what connection does the development of relativity theory have to the world out of which it came? This mirrors the historian’s eternal question: why did this happen then and there? What I am trying to do in the book is to address that question. Why does relativity happen in different forms, in different ways in Paris and Bern at the turn of the century? 

Yerxa: Can you speak to the book’s subtitle, Empires of Time? 

Galison: In many ways Poincaré and Einstein are after something very similar. Both come to that class of ideas we call the Theory of Relativity, but they reason in very different ways. And part of what I want to do is to explain how differently they approach this problem. That requires setting them in different contexts. Part of that difference in context is pedagogical; part of it is a different relationship to physical theories, a different attitude toward the status of physical theories; part of it has to do with differences in their attitudes toward mathematics. They are of different generations. There are many contrasts that one can draw between them, and I am interested in those. But in the subtitle I wanted to point out that in the last third of the 19th century the extension of technical networks was extremely important in the definition of nationhood and empire— the railroad networks, telegraph lines, undersea cables that extended coordinated time across the interior of nations, across national boundaries, and eventually into the colonies. This skein of wires became both a practical and symbolic way of inscribing empire on the world. When a place was mapped— whether in Brazil, Vietnam, Senegal, or the western parts of North America—it was on one level a practical problem of how you laid the grid for railroad lines, mineral extraction, military planning. But it was also a symbolic conquest in which the country that did the mapping imposed its grid of the world, its zero of longitude, and its clockregulated simultaneity onto the regions that were in contest. 

Poincaré was involved with these issues at the height of the great imperial struggle. The French, and Poincaré in particular, were involved in the extension of telegraphic lines and missions of establishing simultaneity (and therefore mapping) into Southeast Asia and South America as well as into Africa. So these were issues that were very central. It’s not an accident that the last time that Count Helmuth von Moltke, whose fame by the end of his life really was unexcelled by anybody in Germany, chose to speak in parliament on the military benefits unified time would have in the mustering of troops. Moltke, who was credited with having beaten the French because he was able to muster hundreds of thousands and eventually millions of troops by railroad and bring them to the front through highly choreographed scheduling, argued that military mobilization was very difficult in the absence of a unified time. But it wasn’t just a practical question. On this von Moltke was clear. When he spoke to the politicians in the period just after German unification, he urged them to unify the new nation’s time, maintaining that the disunified condition of time in Germany was a legacy of the earlier fragmented state of the German nation. His view was that it was necessary, symbolically, for the new nation of Germany to have a unified time, and not to rewrite in clocks the splintered condition that had been its past. 

So coordinating time was always a practical issue, but also more than practical. It was material, but it was also symbolic. And that is something that we see throughout the story that I am interested in telling. Synchronized clocks functioned on a purely practical level: they were crucial for markets, train schedules, mapping, and much else besides; but it is also evident in the world of physics, and at the same time a vital piece of metaphysics. The issue of what time is and how to define simultaneity is always a practical matter, and it is always more than practical. 

Yerxa: What would you like the reader to take away from this book? 

Galison: I’d like the reader to come away with the sense that Einstein and Poincaré didn’t live in isolated bubbles outside of the world. Each of them stood at a kind of triple intersection of technological concerns about the world, theoretical questions about how the world worked, and philosophical issues that troubled both of them all throughout their lives. I’m interested in conveying a sense that there isn’t one foundational layer on which everything else is built. It is not that relativity is really about philosophy and secondarily about physics and technology. It is not at root about technology and only epiphenomenally about theory or philosophy. And it is not just about physics and only accidentally connected to the technology. What I’d like to convey is perhaps captured in the metaphor that I used often in the book of the intersection of a set of roads. The Place de l’Etoile in Paris, for instance, is not really in one of the roads that crosses there. An intersection is defined precisely as the meeting point of these roads. So, if you ask if you are traveling down the road of physics, do you come to this idea of the coordination of clocks, which is my central theme, the answer is yes. If you ask whether people involved in the technology of making maps are producing patents for devices to coordinate clocks along train lines, the answer is again yes. And if you query if the conventional coordination of clocks is an issue for philosophers who are trying to understand the nature of time, the answer, once again is absolutely yes. What is fascinating to me, and what I hope will interest the reader as well, is that a very simple procedure for coordinating clocks—take one clock and synchronize the second by sending an electrical signal between them taking into account the time the signal takes to get from one clock to the other—is an idea that is all at once located dead center within technology, physics, and philosophy. 

Yerxa: Your reconstruction of the worlds that Poincaré and Einstein inhabited in the late 19th century reveals the interconnectedness of theory and practical matters: issues of no small concern to railroad engineers and map makers overlapped with the efforts of physicists and philosophers to grapple with the meaning of time. To what extent have historians tended to view science as the unfolding of theories and ideas and in so doing have failed to pay adequate attention to historical context and what you term “the materiality of science”? 

Galison: Propelled in part by the anti-positivist philosophers, the history of science, especially in the 1960s and 1970s, became a history of ideas, focusing on themes that were outside of the world of experiment. But over the last two decades there has been a reawakening of interest in the local circumstances in which scientific work has been accomplished, with a special attention to experimentation. That turn towards the material world was certainly true for me in How Experiments End but also for much of my generation’s scholarship: Steven Shapin and Simon Schaffer’s important book, Leviathan and the Air-Pump, addressed the history of the air pump and located that history within the broader question of dispute resolution in 17th-century Britain. Another key piece of work was Crosbie Smith and Norton Wise’s Energy and Empire which placed Lord Kelvin in the matrix of industrial, theological, and laboratory work that set the tone for much Victorian scientific culture—here the steam engine and telegraphy mediated between industry and high physics. We’ve begun, in short, to look at science as embedded in the world, through devices as well as experiments. So while my interest began in questions that were broadly epistemological (how experiments and indeed certain instruments shape what counts as a scientific argument, for example), I’m now after something else. I am fascinated by the powerful and often very direct confrontation between very material objects (like clocks that were actually wired along railroad lines) and the abstract reasoning that goes into completion of the Theory of Relativity. I am not interested in displacing the history of ideas or the cognitive content of science in favor of a “foundational” stratum of the material in which science is “nothing other than” the residue of industrial concerns. Instead, what I find most exciting is how the abstract and concrete inform one another. Grasping how the development of very important changes in our theoretical understanding of the world has interwoven with practical material aspects deepens, rather than reduces, our appreciation for the nature and import of those theoretical alterations. 

Yerxa: To what extent is Einstein’s Clocks, Poincaré’s Maps biographical? 

Galison: I’m interested in the figures of Einstein and Poincaré, but this is not a biography of either figure. Einstein’s Clocks, Poincaré’s Maps is not a biography in the sense that it delineates the arena of attention around the proximate bubble of its protagonists —I have no particular interest in the childhood adventures or distant forebears of Einstein and Poincaré, in Einstein’s romantic entanglements, or in his postwar engagement with various causes. Instead, I use these two figures to get at something important about the intersection of technological, philosophical, and physical concerns and practices at the end of the 19th century. In a sense I use (certain) biographical elements to an end that is not in the main biographical. So it does matter to me that Poincaré was simultaneously the most famous mathematician in France, one of the leading physicists, president of the Bureau des Longitudes, and an absolutely central figure in the philosophical community both in France and internationally. So where Poincaré stands is key to me. But his location is important in this book because it picks out this critical intersection of the technological, the physical, and the philosophical. Understanding the conditions under which that intersection could arise and prosper means analyzing, for example, the specific scientific culture of Ecole Polytechnique, where Poincaré was trained and eventually taught. It means understanding the daily practices of work at the Bureau des Longitudes, and it means grasping what an informal grouping of scientifically inclined philosophers were after during these last decades of the 19th century. 

Yerxa: And you studied at Polytechnique as well? 

Galison: Yes, oddly enough I spent a year at Ecole Polytechnique (1972–73) exactly one hundred years after Poincaré. Ecole Polytechnique is an interesting place; it has no analogue in the United States—a kind of cross, if you can imagine such a thing, between West Point and MIT. It is a highly technical school, founded in the time of Napoleon for training leading French civil servants, mathematicians, politicians, generals, and engineers. For several hundred years its great ambition has been to combine a very high level of scientific training in pure mathematics with a superb engineering training. These characteristics of the institution are very important for the story I tell here because it meant that Poincaré emerged from this training prepared to become a mining inspector; he was quite expert in matters associated with mine safety and mining engineering. He remained interested in mining throughout his life. But it was not only mining that held his attention: he immersed himself in a kind of rational engineering across many fields. For instance—and this is relevant to Einstein’s Clocks, Poincaré’s Maps— it was Poincaré who took on the task of evaluating whether it was worthwhile to pursue the old revolutionary ideal of decimalizing time. It was Poincaré who authored some of the early French papers and books on radio technology; and it was Poincaré who helped get the Eiffel Tower wired to be an enormous antenna that could broadcast time signals to navigators and explorers serving the French Empire. So this is someone who is trained in engineering, but a kind of engineering that is far from the tinkerer, home-grown inventor, or purely pragmatic designer. Poincaré was early on immersed in a rational engineering, if you will; an engineering informed by very strong mathematical and scientific training. 

I was seventeen when I came to Ecole Polytechnique—I worked as a research student at a plasma physics laboratory and studied with one of the great mathematicians of our era, Laurent Schwartz. Witnessing firsthand this combination of an extremely high level of mathematics with very practical concerns made an impression on me and perhaps gave me some empathy for what this institution had been up to in its very central role in the reconstruction after the Franco- Prussian War of 1870–71. No doubt, having spent a year with the students and scientists of Ecole Polytechnique contributed to my fascination with the ambitions of the institution in the time of Poincaré. 

Yerxa: Would you place time—the concept of time—in some historical and historiographical context? 

Galison: There is, of course, some wonderful work on the history of time. Jacques Le Goff’s Time, Work, and Culture in the Middle Ages comes to mind; Dohrn-Van Rossum’s terrific book, History of the Hour, and of course my colleague here at Harvard, David Landes’s Revolution in Time. More recently, some younger scholars have begun to take up questions surrounding coordinated time in its cultural setting—Jakob Messerli, for instance. One of the things that we learn from the scholars studying the late medieval period is that around the 14th century, as clocks begin to be installed in public places, the symbolic and the practical are quite con-nected. I find that tremendously interesting. The dominion of the feudal lord would be established over the range in which it was possible to hear the bells of a clock. Clocks were seen to be a representation of a natural, God-given order, as well as regulators of behavior and signs of secular power. People recognized different kinds of time, as Dohrn- Van Rossum has documented. We learn through some of this scholarship, for instance, that there was a time of punishment: clocks or hourglasses were used to determine how long someone could be subject to certain tortures. There was a time for how long one had to present a case in front of a judge. In addition to many different kinds of time, there were also many different symbolic registers of time: time as being the memory of our finite existence, the role of clocks and hourglasses in paintings as symbols of mortality. There was a movement back and forth between different practical uses of time, but always with a symbolic overlay. In that sense what I am doing resonates very strongly with this riveting and fairly recent way of looking at the history of time, especially from the late Middle Ages onward. 

Yerxa: And in what ways was the notion of time itself altered by the work of Poincaré and Einstein? 

Galison: Time changes when you get to the last third or so of the 19th century. Suddenly —and this is immensely striking to many contemporaries of Poincaré and Einstein —time is brought down from a domain beyond ours. When Poincaré or his contemporaries say that time is a convention, there is a realization that we have a choice about time, and that in our ability to fix the basis of duration and simultaneity we find that our time, as we have access to it, is all there is to time. For Newton, and indeed for anyone in the 17th century or before, the measure we make of time is but a poor approximation of something purer and higher than that to which we have access. Newton points insistently to the difference between mathematical and absolute time, on the one side, and the relative practical time that clocks actually measure, on the other. The idea of making time and time synchronization conventional is that there isn’t a time behind the times that are measured. There isn’t a hidden absolute world in back of the screen of “mere” appearances. This comes up as a practical matter, for instance, in astronomy even before relativity. Astronomers knew that if they defined the basic unit of time to be the rotation of the Earth on its axis, then they found that pendula (and every other physical process) were speeding up. By contrast, if they decided that a pendulum was a constant basis of time measurement and therefore defined the basic unit of time, then they would discover that the Earth was slowing down on its axis. For Poincaré and his philosophically- minded scientist colleagues, God did not come down and tell us that one of those choices (pendulum swing or Earth rotation) must be the right basic unit of time. We must make a choice. And as Poincaré and his contemporaries recognized, we’re better off taking the pendulum as our basic unit because that is the simpler choice. We can then try to account physically for why the Earth is slowing down—because tidal forces dissipate the Earth’s rotational energy. The alternative presented a hopeless scientific problem: taking the Earth to be rotating constantly on its axis and (somehow) explaining why every other natural phenomenon of nature was speeding up. In such choices came the realization that there was no Archimedean point outside of the world from which an absolute time-fixing motion of the universe could be chosen. 

Both Poincaré and Einstein pushed hard for understanding time in this conventional way. Both understood that simultaneity is something that is established procedurally and by agreement. So the short answer to your question would be that in mixing symbolic and concrete issues, the history of time that I am giving here—this period of synchronization in philosophy, physics, and technology—brings a dramatic new understanding of time. But in a sense, the constant back and forth between practical and symbolic registers of timekeeping is indeed consonant with a history of time stretching back into the late Middle Ages. 

Yerxa: What is the connection between Einstein’s Clocks and your previous work? 

Galison: My work in its broadest sense is about looking at physics not as a simple entity, but as an entity composed of different subcultures, subcultures that are differently attached to the wider world around us. For instance, instrument makers working at CERN (the European Organization for Nuclear Research) on the French-Swiss border seem to be immersed in the world of particle physics. And in a way they are part of the world of particle physics, but they share a material culture—a set of instruments, a set of concerns—with people doing things that have nothing to do with particle physics (e.g., people designing hardened electronics for use on the nuclear battlefield because that is the only other place aside from particle physics where people have to worry about massive irradiation of extremely sensitive electronic devices). So the people making those machines live in part in a world that they share with theorists and in part in a world they share with machine and electronic engineers who have nothing to do with physics. I have also been interested in the way theorists are attached differently to the world than experimentalists, how experimentalists find certain kinds of devices and arguments persuasive and others not. Theorists may share concerns and techniques with mathematicians, for instance, or with philosophers worried about the nature of conventional knowledge, causality, or space and time. So I am interested in the specific ways in which the parts of physics are connected to one another, and in the connection of physics to the wider world beyond physics. 

The first book that I wrote, How Experiments End, was about how experimental physicists decide they are looking at a real effect and not an artifact of the machine or apparatus. It showed that what persuaded an experimenter was not necessarily that which persuaded a theorist—the two worlds moved with their own rhythms and with their own breaks and continuities. My next book, Image and Logic, was about two vast traditions of instrument making in physics. One tradition made machines that produced pictures (for instance, the cloud chamber, the nuclear emulsion, or the bubble chamber). And another competing tradition wasn’t looking so much for that detailed picture of things as it was for statistical counts, for logical connections between events that would be persuasive for them. These two traditions rivaled one another, each suspicious of the other over many decades. Eventually, in the 1970s and 1980s, the logical tradition and the visual tradition came together in devices that could combine the pictorial and the ability to manipulate objects at the same time. That was Image and Logic: A Material Culture of Microphysics. 

And Einstein’s Clocks, Poincaré’s Maps is the first part of an effort to try to extend this kind of argument to the third major subculture of modern physics, theory: that most abstract of our knowledge of the outside world. My hope was to bring theory into the picture in a way that would underline its abstraction and yet set it in relation to very concrete circumstances. But perhaps that is a continuing theme through all my work: I am fascinated by what we can learn as we move back and forth between machines and theories. Or alternatively, perhaps, we need to learn to look at the great movements in theory and understand them as machine-like, while we grasp material culture as a form of theory. 

Yerxa: What are you doing next? 

Galison: Well, I have a couple of things I am working on. A colleague, Lorraine Daston, and I are finishing a history of scientific objectivity that we’ve worked on for many years: Images of Objectivity. We’re tracking the idea of objectivity through the history of those compendia of images that define the working objects of science: scientific atlases. And then I am trying to finish a book about “theory machines,” looking at what has happened in physical and theoretical science over the last several years. On one side, I am interested in how theoretical physics has moved toward the more abstract (joining string theory and mathematics) and, on the other side, toward engineering with the development of nanoscience (joining physics, biology, chemistry, and engineering). 

Yerxa: Einstein’s Clocks has received a lot of attention. In particular, I note that a British reviewer has called it “perhaps the most sophisticated history of science ever attempted in a popular science book.” Who was your intended audience? 

Galison: I originally had thought I was writing the first part of the third volume of the trilogy that began with How Experiments End and continued in Image and Logic. Einstein’s Clocks, Poincaré’s Maps emerged from what was going to be the first chapter of this Theory Machines. But at a certain point I realized that this story made a self-contained whole. I started out with Einstein and then began to wonder whether there was anyone else at this three-fold crossing of technology, physics, and philosophy. Rather dimly, I remembered a line in one of Poincaré’s essays where he alluded to telegraphy as he explained how simultaneity ought to be defined. But the book really took form when I found (in the Parisian archives) that Poincaré had played a significant role in the Bureau des Longitudes —then I could see that the parallels (and anti-parallels) between Einstein and Poincaré could be used to frame a story that was both a broader history and a very different kind of history of relativistic time. By structuring the text around the confluence of these various time coordination efforts (rather than an encyclopedic history of the special theory of relativity) I also realized that I could tell this story exactly the way I wanted to—with the methodological sophistication I was after but without the equations that a history of electrodynamics would require. So I took it as my goal—whether it succeeded or not others will have to judge— to write a book that was not a popularization in the sense of being a vulgarization of something that I had done in a more sophisticated way elsewhere. That is, the book is not a popularization if one means by popularization the translation of scholarly results into simplified terms. To be honest, I don’t have two or three years to spend on that kind of project. This had to be—for me—something that represented what I had done in the best way I was capable. And in any case, I was convinced that at least some readers would like a book about physics that assumes a sophisticated audience interested in ideas— just not an audience at ease with differential equations. But I did spend a tremendous amount of time just working on the writing. In fact, the last year of work on the project was devoted almost entirely to writing and rewriting the text in order to evoke a time and place where linked clocks mattered. My aim was to do it in a way that captured the relevant pieces of physics and philosophy, brought them forward with my historiographical and theoretical ambitions intact, and yet skipped the turgid prose of pedantic exposition. I wanted very much for the book to be self-contained. So it is a piece of popular science writing, if you will, in the sense that I did not want to cut off part of the audience that would be interested in it just so I could have the satisfaction of writing down equations. For this book I didn’t think that was necessary. I held tenaciously to the idea that if I wrote it well enough, carefully enough, I could capture the ideas in a way that physicists would recognize as well as historians or philosophers—for that matter, people from any background who want to understand more about time and space at just that turning point where these concepts came down from Newton’s absolutes to the very earthbound conventions of technology, relativity, and scientific philosophy. 

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