"I'm interested in bending the edges of the spectrum to make the abstract and the concrete hit one another more directly." — Peter Galison
120June 24, 2003
EINSTEIN AND POINCARÉ: A Talk with Peter Galison
After learning more about Poincaré I tried to understand how he and Einstein could have radically reformulated our ideas of time and space by looking at the way that philosophically abstract concerns, physics concerns, and these technological problems of keeping trains from bashing into each other and coordinating mapmaking across the empires might fit together into a story. I began with an extraordinarily simple idea: that two events are simultaneous if I can make clocks at the two events say the same thing. How do I coordinate these clocks? I send a signal from one to the other and take into account the time it takes for the signal to get there. That’s the basic idea, but all of relativity theory, E = mc2, and so much of what Einstein does follows from it. The question is, where did this idea come from? Albert Einstein and Henri Poincaré were the two people who worked out this practical, almost operational idea of simultaneity, and I want to see them as occupying points of intersection of technological, philosophical, and physical reasoning. They were the two people who were at those triple cross-sections. [continued below]
THE THIRD CULTURE — BRIEFLY NOTED
[Editor's note: Andrew Marr is host of Start the Week, the leading cultural magazine program on British radio, a former Editor of The Independent, and the present BBC Television Chief Political Correspondent.]
EINSTEIN AND POINCARÉ: A Talk with Peter Galison
I tried to understand how Poincaré and Einstein radically reformulated our ideas of time and space by looking at the way that philosophical abstractions, physical theories, and the technological problems of keeping trains from bashing into each other and coordinating mapmaking across empires might cross in a single story. I began with an extraordinarily simple idea that marked the last century: two events are simultaneous if coordinated clocks at the two events say the same thing. How do I coordinate these clocks? I send a signal from one to the other and take into account the time it takes for the signal to get there. That’s the basic idea, but all of relativity theory, E = mc2, and so much of what Einstein does followed from it. The question is, where did this idea come from? Albert Einstein and Henri Poincaré were the two people who worked out this practical, almost operational idea of simultaneity, and I want to see them as occupying points of intersection—of technological, philosophical, and physical reasoning. They were the two people who stood at those triple cross-sections.
Peter Galison, Professor of the History of Science and of Physics at Harvard, asks how Poincaré and Einstein "could have radically reformulated our ideas of time and space by looking at the way that philosophically abstract concerns, physics concerns, and ... technological problems of keeping trains from bashing into each other and coordinating mapmaking across the empires might fit into a single story."
Regarding Einstein’s and Poincaré’s account of simultaneity, he wonders: "Is it really physics, or fundamentally technology, or does it come down to philosophy?" He calls it "an extraordinary moment when philosophy, physics and technology cross, precisely because of the intersection of three very powerful streams of action and reasoning at the turn of the century."
This moment resonates with many recent discussions on Edge, and to what Galison terms "the collection of sciences that have grown up around computation. Here, ideas about the mind, about how computers function, and about science, codes, and mathematical physics all come together. Von Neumann thinks about the mind and its organs (memory, input-output, processing) as a way of designing a programmed computer. The programmed computer then becomes a model for the mind. The ideas of information, which are encoded into the development of computation, also become ways to understand language and communication more generally, and again feed back into devices. Information, entropy, and computation become metaphors for us at a much broader level."
Convergences such as Einstein’s and Poincaré’s account of simultaneity or new the sciences of computation are "opalescent moments" that "point to science in times and places where we’re starting to think with and through machines at radically different scales—Where we are flipping back and forth between abstraction and concreteness so intensively that they illuminate each other in fundamentally novel ways, in ways not captured by models of simple evaporation or condensation. When we see such opalescence, we should dig into them, and deeply, for they are transformative moments of our cultures."
Two collections of interpretive essays have been published about Image and Logic, which also won the Pfizer Prize for Best Book in the History of Science. For his work on these books he was awarded a MacArthur Fellowship in 1997, and a Max Planck Prize by the Max Planck Gesellschaft and Humboldt Stiftung in 1999.
Peter Galison presents his new book: Einstein's Clocks and Poincaré's Maps: Empires of Time:
True time would never be revealed by mere clocks—of this Newton was sure. Even a master clockmaker's finest work would offer only pale reflections of the absolute time that belonged not to our human world, but to the "sensorium of God." Tides, planets, moons—everything changed, Newton believed, against the universal background of a single, constantly flowing river of time. In Einstein's electro-technical world, there was no place for such a "universally audible tick-tock" that we can call time, no way to define time meaningfully except in reference to a definite system of linked clocks...Two events simultaneous for a clock-observer at rest are not simultaneous for one in motion. With that shock, the foundation of Newtonian physics cracked; Einstein knew it. Late in life, he interrupted his autobiographical notes to apostrophize Sir Isaac as if the intervening centuries had vanished; reflecting on the absolutes of space and time that his theory of relativity had shattered, Einstein wrote: "Newton, forgive me; you found the only way which, in your age, was just about possible for a man of highest thought and creative power."...At the heart of this radical upheaval in time lay an extraordinary yet easily stated idea that has remained dead-center in physics, philosophy, and technology ever since: To talk about simultaneity, you have to synchronize clocks with a flash from one clock to another, adjusting for the time that the flash takes to arrive. What could be simpler? Yet with this definition of time, the last piece of the relativity puzzle fell into place, changing physics forever.
EINSTEIN AND POINCARÉ
(PETER GALISON:) When the Einstein centenary was celebrated in 1979 the speakers at all of these great events spoke about physics only as theory. It seemed odd to me that somebody like Einstein, who had begun as a patent officer and who had been profoundly interested in experiments, had left such a thoroughly abstract image of himself. My interest in Einstein began in that period, but beyond Einstein I was intrigued by the startling way that experiment and theory worked together, fascinated by the abutting of craft knowledge hard against the
For quite a number of years I have been guided in my work by the odd confrontation of abstract ideas and extremely concrete objects. Science history, sociology, and epistemology are for me very connected, and the kind of work that I do in the history of science is always propelled and illuminated through philosophical questions. For example, I am interested in what counts as a demonstration. What does it mean to be done with a demonstration? How do experimenters distinguish between a real effect and artifacts of the apparatus or the environment? We think we know what it means to conclude a mathematical deduction, but what does it mean when I’ve shown something with a computer simulation? If I do a simulation and show that the tail of a comet forms into islands, have I demonstrated that, or is my result just the beginning of an explanation that then needs a more analytic mathematical derivation? These are questions that even today puzzle across a myriad of fields. They are questions that are, inevitably both historical and epistemological — that is they are about ordinary scientific practice and yet fundamentally philosophical. When I choose to work on a problem it is usually because it is illuminated by these different beams of light, so to speak.
When I and a few other historians, sociologists, and philosophers began looking at instruments and laboratories back in the late 1970s, emphasizing experimentation in the history of science seemed rather odd. Most historians and philosophers were keen (in the aftermath of Thomas Kuhn’s work) to show that all of science issued from theory. I suppose it was a kind of reaction against all those years of positivism from the 1920s through the 1950s when philosophers insisted that all knowledge came down to perception and observation. In any case, there wasn’t really a body of serious work on what a laboratory was, where the lab came from, or how it functioned. Since then, inquiry into the history and dynamics of experimental practice has grown into much larger domain of study. I am interested not just in the laboratory itself, however, but also in the most abstract kinds of theories. Recently, for example, I’ve been writing about string theory—specifically the confrontation between physicists and mathematicians as they try to sort out what ought to be a demonstration—in what is without doubt the most abstract form of science ever pursued.
But in every instance I’m above all intrigued by how philosophical questions illuminate and are illuminated by very the practices of science, sometimes material, sometimes abstract. And I suppose that I am always interested in blasting away the mid-level generalizations, and to explore, as in Einstein’s Clocks, Poincaré's Maps, at the way the most abstract and the most concrete come together. Instead of thinking of a kind of smooth spectrum that goes from ultraviolet to infrared with everything in between, I’m interested in bending the edges of the spectrum to make the abstract and the concrete hit one another more directly.
I began my work quite a number of years ago, the
history of science was focused almost exclusively
the history of ideas and theories. Experiments
and instruments, to the extent that they were
to anybody, were peripheral helpmates to the
production of theory. I began by being interested
in the way
that certain kinds of instruments, or the way
were used, shaped the way knowledge worked and
the kinds of questions that people were asking.
book, How Experiments End, was about how experimentalists
decide that they’re looking at something
real, whether it’s using a small scale
table-top device or a huge experiment involving
My interest in the materiality of science goes back to my childhood. My great-grandfather, who lived until his mid-90s, trained in Berlin and worked in Thomas Edison’s laboratory as an electrical engineer, and I spent a great amount of time with him in his basement laboratory. I was completely riveted by what he did. It was the kind of laboratory that you could imagine in a film about Dr. Frankenstein, with giant double throw switches, arcs of electricity in the dark space, and bottles of mercury lining the shelves. I loved every bit of it. I left high school when I was 17 to study physics and mathematics at the Ecole Polytechnique in Paris for a year. I had a chance to learn from one of the great mathematicians, Laurent Schwartz. I’d been to France a fair amount, spoke French, and wanted to go there because I was very interested in European politics—these were wild times politically—towards the end of the Vietnam War. I thought that the only chance I had of working in an interesting place would involve pursuing something in physics, so I wrote to various physics laboratories, and they must have taken me out of amusement at the idea of this American 17-year-old writing to the Polytechnique.
When I began I was interested in philosophical questions, and thought that studying physics was a way to get at some of these problems. I worked in a laboratory on plasma physics, which is now done in gigantic machines in huge laboratories, although at the time it was still possible to do small-scale experiments on devices not much bigger than a table. I became quite fascinated with the machinery, the signal generators, recording devides, oscilloscopes, and how theoretical knowledge about the world could come out of such material objects. In college at Harvard I found a way, having done a fair amount of physics, to combine it with history and philosophy.
This brings me back to Einstein.
The Einstein we know today is mostly based on Einstein’s later years, when he prided himself on his alienation from practically everything sociable and human, projecting an image of himself as a distracted, other-worldly character. We remember that Einstein who said that the best thing for a theoretical physicist would be to tend a lighthouse in quiet isolation from the world in order to be able to think pure thoughts. We have this picture of the theoretical physicist, and project it backwards to Einstein’s miraculous year, 1905. It is easy enough to think of him as working a day job in a patent office merely to keep body and soul together, while in actuality his real work was purely cerebral. Such a split existence never made sense to me; I wondered how his work in the details of machines and objects might connect to these abstract ideas, and began thinking about how relativity itself might have been lodged in the time, place, and machinery in which it was created.
day in the summer of 1997—I
was in a train station in northern
Europe, looking down the platforms
at these beautifully arranged clocks.
The minute hands were all the same.
I thought, “God,
they made these extraordinary clocks
back then. What an extraordinarily
wonderful piece of machinery!” But
I then noticed that the second hands
were also all clicking along in sync.
That meant the clocks were
too good. So I thought that maybe they’re
not good clocks — maybe they’re
synchronized clocks bound together
by electrical signals that
advanced them together, in lockstep.
Maybe Einstein had seen
such clocks when he was writing his
paper on relativity.
So I began to look further, wondering who else would have been worrying about simultaneity in the late 19th century. It turns out that the great French philosopher, mathematician, and physicist, Henri Poincaré, had much the same idea as Einstein. He also wanted to criticize the idea of absolute simultaneity and to make it something that could be measured. Instead of trains and stations, Poincaré chose for his key metaphor the exchange of a telegrapher’s signal down a line. In his famous philosophical article of January 1898, Poincaré says that simultaneity is really just the exchange of signals, like two telegraphers trying to determine how much longitudinal difference there is between them. You see, if the earth were stationary, we could find our longitude simply by looking up to see which stars were straight above us. But the earth turns, so to compare two longitudes, that is the stars above two different sites, you have to make the measurement at the same time. Consequently, for centuries map-makers have worried about simultaneity and how to determine it. By the late 19th century people were exchanging electrical time signals across the oceans via undersea cables, and what is interesting is that Poincaré was right in the middle of it — in 1899 he was elected president of the Bureau of Longitude in Paris. Then, in December 1900, he brought his new definition of time from philosophy and technology into the heartland of physics. He showed that if the telegraphers coordinated their clocks when moving through the ether, their clocks would “appear” to be simultaneous even though from the “true” ether-rest system they were not. But now the new definition of simultaneity stood central for Poincaré in all three domains: philosophy, technology, and physics.
Though Poincaré was as famous as any mathematician or philosopher of his time, he was also a man of enormous engineering skills, trained as a sophisticated engineer at the Polytechnique and Ecole des Mines in Paris and later becoming one of Polytechnique’s most illustrious professors. It is Poincaré’s situatedness that intrigues me: like Einstein, when Poincaré invoked the longitude-finding telegraphers, he was speaking both metaphorically and literally. He was changing a central concept for all physics and at the same time addressing the real practices of map-makers.
Though less well known by far than Einstein, at the turn of the century Poincaré’s popular philosophical books, Science and Hypothesis and Science and Values, were bestsellers in France. They had a profound effect on modern philosophy of science, and today are still read in philosophy courses. They were also translated into many other languages very early on, including German and English, and were widely distributed. He opened up whole new areas of mathematics, including the mathematics of topology. He helped invent the science of chaos, and all that we understand of the science of complexity owes an enormous amount to him. He contributed enormously to what became relativity theory, and is important in many other branches of physics. He was truly a polymath and went on to do things in engineering. He was one of the people who rescued the Eiffel Tower from being taken down after the International Exhibition for which it was built, because he saw a way of using it as a military antenna. In fact, in large measure under Poincaré’s direction, the Eiffel Tower itself became an enormous antenna that would send time signals all over the world, allowing longitude finders from Canada to the tip of Africa to do their work. Moving back and forth smoothly between high engineering and abstract mathematics, he left an enormous legacy across many fields, always reasoning concretely, visually—as an abstract engineer so to speak. His thoughts on time were no exception.
After learning more about Poincaré, I tried to understand how he and Einstein could have radically reformulated our ideas of time and space by looking at the way that philosophically abstract concerns, physics concerns, and these technological problems of keeping trains from bashing into each other and coordinating mapmaking across the empires might fit into a single story. It begins with an extraordinarily simple idea: that two events are simultaneous if I can make clocks at the two events say the same thing. How do I coordinate these clocks? I send a signal from one to the other and take into account the time it takes for the signal to get there. That’s the basic idea, but all of relativity theory, E = mc2, and so much of what Einstein does follows from it. The question is, where did this idea come from? Albert Einstein and Henri Poincaré were the two people who worked out this practical, almost operational idea of simultaneity, and I want to see them as occupying points of intersection of technological, philosophical, and physical reasoning. They were the two people who stood dead center in those triple crossing points.
Sometimes people ask me, what is really at the base of Einstein’s and Poincaré’s account of simultaneity? Is it really physics, or fundamentally technology, or does it come down to philosophy? I think that those are wrong ways of putting the question. That is to say, to me it’s like asking if the Place de l’Etoile is truly in the Avenue Foch or the Avenue Victor Hugo. The Place de l’Etoile is a place because it is at the intersection of those great avenues. And that’s what happens here. We’re looking at an extraordinary moment when philosophy, physics and technology cross, precisely because of the intersection of three very powerful streams of action and reasoning at the turn of the century. It is like having a triple spotlight focussed on one position in an enormous theater; it’s triply illuminated. It was important to railroad engineers and map makers that they knew how to define simultaneity. It was important to philosophers to figure out what time is, what a clock is, and how to think about what defined time: mechanical clocks or astronomical phenomena or some sort of abstract time that lay behind all appearances. And it was important to physicists to understand what simultaneity was in order to know how to interpret the most important equations of physics: Maxwell’s equations concerning electricity and magnetism. Poincaré and Einstein were the two people—more than anyone else—who were concerned with all three parts of that intersection, and that is why they need to be understood together. Of course clocks did not cause relativity any more than relativity caused the transformation of modern clock synchronization.
In human terms, Einstein and Poincaré are fascinating because in some ways you couldn’t imagine two people closer. They had common friends, published in many of the same places, and were working intensively on many of the same problems. They were both at the top of their professions, both enjoyed writing for broader audiences, both were taken very seriously by philosophers, and both had serious technological-engineering interests and training. Yet they couldn’t have been farther apart. In a certain way they remind me of Freud, for whom it was almost unbearable to read Nietzsche, because (as Freud said on several occasions) Nietzsche’s ideas were too close, and yet organized around a different approach.
Poincaré and Einstein, who had two of the largest scientific correspondences of the 19th and 20th centuries, including thousands of letters to and from other people, never exchanged a single postcard over the entirety of their overlapping lives. They met once, towards the end of Poincaré’s life, when Poincaré presided over a session at a vitally important physics conference where Einstein was talking about his new ideas about the quantum of light. At the end of this session, Poincaré said that Einstein’s presentation was so different from what physics should be — namely that it could be represented with causal interactions, with good differential equations, with clear presentations of principles and consequences — that he simply found it unbearable, and ended by making it clear that what Einstein was saying was so contradictory that anything could follow from it. It was a disaster for science, he thought. Einstein for his part went home and scribbled a note to a friend in which he recounted the wonderful work that had been done by various colleagues, how much he admired, even loved, the physicist Hendrik Lorentz, but disparaged Poincaré who simply seemed to understand nothing. The passed like ships in the night, each, on relativity, unable to acknowledge the other’s existence. Yet a few weeks after their ill-starred meeting, Poincaré wrote a letter of recommendation for Einstein for a job that was very important to him. It was a stunning letter that said, essentially, that this young man may well be up to some of the greatest things, and even if only a few of his wild ideas turn out to be true he’s a person of extraordinary importance. It was a letter of enormous grace and generosity. They never directly exchanged another word and never met again.
The contrast between Einstein and Poincaré, and their different understandings of what they were doing represent two grand competing visions of modern science for the 20th century. Although the equations that Poincaré and Einstein come up with around relativity theory are very similar — essentially identical — Poincaré always thought of what he was doing as fixing, repairing, or continuing the past by applying reason to it by. As one of his relatives once put it, he was filling in the blank spots on the map of the world. Einstein was willing to do things rather differently, to say that the old way of proceeding is too complicated, too filled with piecemeal solutions, and that what we need is something that starts over again with the classical purity of a few stark principles. Poincaré saw himself in some ways as saving an empire—the empire of France, no doubt, but also the empire of nineteenth century physics. His was a grand ambition, but it’s a different kind of modernism from Einstein’s. It’s a reparative, ameliorative modernism, a modernism with all the rational hopefulness of a third Republic Frenchman. Einstein’s is a much more disruptive, classifying, purifying modernism. It is only by understanding this triple intersection of philosophy, physics, and technology that one can really grasp what each of these alternative visions of the new century is about.
might ask, and
I’ve often wondered,
how to think about
this kind of event
in the present. That
is to say, is there
an analogy now to this
Here is how I think
about it: When you
consider Poincaré and
dealing with an attempt
to understand time
coordination and the
clocks at a huge variety
of scales. In some
trying to figure out
how to coordinate clocks
inside a single room
observatory, or a block,
or a whole city, at
the same time that
the people who are
worried about these
are also sending cables
across the Pacific
and Atlantic Oceans.
Einstein and Poincaré are
not just worrying about
such planetary scales,
but also about how
coordinate clocks in
frames in the universe
as a whole. They are
asking, what does
What does simultaneity
mean? These are questions
that occur at every scale, from
the smallest to the
largest, from philosophy
and physics all the
way down to electrical
wiring along train
In that sense it is
unlike most questions
that we ask in science,
since it doesn’t
have the character
of starting out as
something purely abstract
becomes applied physics
and engineering, eventually
ending up on the factory
floor. It’s also
not a platonic ascension,
or a naive version
in which machines and
machine shop relations
are slowly abstracted
to ever wider spheres
a theory of the universe.
the kind of metaphor
that we need to look
at a situation like
this. Poincaré and
Einstein are flipping
back and forth between
and practical questions.
end of the 1890s
publishing in journals
for map makers and
the same time he
was publishing in
in the Journal
In his thinking he
was and flipping
back and forth
quickly between these
three domains of