Saturday, May 19, 2007

Galison: Poincare and Einstein

A colleague and I recently discussed Peter Galison and his book Einstein's Clocks, Poincare's Maps: Empires of Time . (See also here and here.) The book explores how practical concerns of the era (in particular, clock synchronization -- important for longitudinal navigation as well as for the European train system) influenced the discovery of special relativity.

Both my friend and I are great admirers of Galison. After earning his doctorate in the history of science, he wrote a second dissertation in particle theory under Howard Georgi while a Junior Fellow at Harvard. Other than particle theorists turned science historians like Sam Schweber or Abraham Pais (see here and here), I can't think of anyone more qualified to work on the (underdeveloped) history of modern physics.

When I learned about special relativity as a kid, I first went through a phase of suspicion about Einstein's operational approach -- how could one be sure, I wondered, that light beams were the best primitive for the operation and synchronization of clocks? After I accepted this idea, I was shocked that someone could be so imaginative as to come up with his clever gedanken experiments, involving moving trains, light beams, lattices of clocks. I thought to myself -- I could have never invented that! It was only much later that I learned about his patent office work on clocks and how synchronization of time between distant rail stations was an important practical problem of the day. I agree completely with Galison that practical concerns had a strong influence on both Einstein's and Poincare's thinking.

NYTimes: ...Einstein's relativity has long been regarded by scholars as a monument to the power of abstract thought. But if Dr. Peter Galison, 48 -- a Harvard professor of the history of science and of physics, a pilot, art lover and nascent filmmaker -- is right, physics and Einstein have flourished more in their connections to the world than in any ivory tower aloofness. And one clue to the origin of relativity can be found in something as mundane and practical as a 19th-century train schedule. ''It's in as plain sight as it could possibly be,'' he said.

As Dr. Galison relates, before the advent of factories began to standardize life, and railroad systems with crisscrossing tracks made it imperative to know which train was where and when, there were too many times, one for every village.

In the last part of the 19th century, the coordination of clocks and the standardization of time had engaged the passions of nations, business leaders, astronomers and philosophers. The patent office in Bern, Switzerland, where Einstein worked, was a clearinghouse for patents on the synchronization of clocks.

In New England, the Harvard and Yale observatories were competing to sell time signals to the public, and in Paris pneumatic tubes snaked under the streets to synchronize the city's clocks with blasts of air. Far from being a bit of abstraction by a loner genius, the clocks that Einstein used as examples in his papers were as familiar then as computers are today.

...In addition to all his high-flown academic activities, Poincaré was immersed in practical work. He was a mining inspector, for example. Most important, he was deeply involved with the French Board of Longitude, even serving as president, sending teams of soldiers and surveyors across the oceans to map the far-flung empire.

Coordinated clocks were central to this enterprise. To measure the longitude of some mountain or port or gold mine in the New World, it was necessary to measure the difference between the time some star crossed the meridian there and the time it did back in Paris. The leaders and rivals in filling in this ''electric world map,'' as Dr. Galison calls it, were England and France, even though for several years they were embarrassingly unable to agree on the distance between their own principal observatories, Greenwich and Paris. Paris lost out to Greenwich as the locus of zero longitude, but in 1909 Poincaré used the Eiffel Tower to broadcast time signals to the world.

...In his papers Einstein was always using modern machines to illustrate his ideas, Dr. Galison noted. ''There is something wonderful about Einstein invoking trains and telegraphs to get a transformation of space-time, Poincaré turning the Eiffel Tower into a radio,'' Dr. Galison said.

''In the long run I think what's happened to them is that we, partly through our own doing and partly through our doing to them, removed these physicists from the concrete situations that they were involved in. And I think in a way lose some of the fascination that these ideas had for them and still could have for us in a way.''

It's our loss, he said.

Galison: "My question is not how different scientific communities pass like ships in the night,'' he wrote in Image and Logic. ''It is rather how, given the extraordinary diversity of the participants in physics -- cryogenic engineers, radio chemists, algebraic topologists, prototype tinkerers, computer wizards, quantum field theorists -- they speak to each other at all."

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