# Space-Time Einstein!

By Michael D. Gordin

It is once again time to talk about time. On March 14, 1988, Larry Shaw of the San Francisco Exploratorium organized the first official “Pi Day” to celebrate mathematics (and also, for the broad minded, physics). Ever since, slowly but surely, on the day before the Ides of March descend with their overtones of political assassination, a movement has built to extol the ratio between the circumference and diameter of the circle. In 2009, two days before the advent of that year’s Pi Day, the United States House of Representatives passed a resolution (alas, non-binding) commemorating the festivities.

The action of a branch of the U.S. government is fitting, since there is something very American about how this is all arranged. March 14 is designated Pi Day because in the month/day format it is written as 3/14, which is the beginning of the representation of the ubiquitous mathematical ratio π = 3.1415926… (Don’t hold your breath. It goes on forever, so devoid of pattern that we designate numbers like π as “irrational.”) Most places in the world, however, do not use the month/day format, but rather day/month. That would mean we would have to celebrate Pi Day either on the third day of the fourteenth month or the thirty-first day of April, neither of which happens to exist. So March 14 it will remain!

There’s another reason why the mathematically-minded and physics-fond settle on March 14: on that date in 1879, in the Southern German town of Ulm, Albert Einstein was born. Princeton, New Jersey, where I live, acquires an Einstein-themed tinge during the run-up to Pi Day, flourishing into a flock of impersonators for the event itself.

This year’s Pi Day in its Einsteinian incarnation fixates as always on a date, a moment of time: the 141st anniversary of the physicist’s birth. But if Einstein’s physics has taught us anything, it is that we should always think of time alongside space. In relativistic physics — which is the only physics we have, even though the effects are so marginal that you may not notice them if you are living on Earth and moving at regular speeds — space and time interpenetrate. As shown in the special theory of relativity, if you move very, very, very quickly, time slows down and lengths expand. With general relativity, Einstein’s theory of gravitation, the consequences of the commingling of space-time are even more pronounced, especially if you happen to be in the vicinity of a black hole.

We can extend the notion of space-time metaphorically, and reflect a bit on the spaces that Einstein himself occupied at various times. Obviously, how deeply you go with this depends quite a lot on your familiarity with Einstein’s biography, but there are three places that leap out for many of his fans:

• Bern, Switzerland, June 1902–October 1909: From his post at the patent office in the Swiss capital, Einstein in 1905 experienced his “miracle year,” leading to three extraordinary papers on special relativity, the quantum theory of light, and Brownian motion, transforming the physics of the twentieth century.
• Berlin, Germany, April 1914–December 1932: During the difficult days of World War I and especially in the liberal environment of the German capital in the democratizing “Weimar Era,” Einstein became a global celebrity, one of the most famous residents of this central city.
• Princeton, New Jersey, October 1933–April 1955: This was the last place Einstein lived, but it was also his longest residence, as he began his term as one of the first faculty members at the newly-created Institute for Advanced Study.

There’s nothing wrong with these places (I’ve spent quite a lot of time in two of them myself), but they do not exhaust Einstein’s space-times. What about Ulm, where he spent his first year? Or his summer houses in Caputh, outside Potsdam, and on Long Island, which he visited for many years when he lived in Germany and the United States, respectively? You could get even more granular. Einstein enjoyed vacationing on the coast of Belgium and also in rural Northern Germany, on the border with Denmark. A recent book by Andrew Robinson, Einstein on the Run (Yale University Press), explores the connections between the physicist and Britain, especially Oxford, which hosted him on several occasions before he fled Europe and settled in America.

This Pi Day, however, I would like to suggest a less well-known space-time: April 1911 to August 1912, the city of Prague, the capital of medieval Bohemia and the present-day Czech Republic, and — in Einstein’s time there — the third city of the sprawling empire of Austria-Hungary. For three semesters, Einstein taught mathematical physics at the German University in Prague, his first appointment as a full professor. In most biographies, these sixteen months are passed over as an “interlude” or “sojourn,” and not taken very seriously. But compressed moments of space-time can hold their surprises. Prague was where Einstein began to work in earnest on general relativity. It was also where he first encountered Zionists, and saw his first marriage begin to fall apart and the genesis of his second. The connections he made in that city both during his stay and afterwards — to writers, philosophers, political leaders — continued to resonate for him long afterwards.

One lesson of Einstein’s science and his life is that it always helps to change your perspective, whether about an onrushing light wave or the obligations owed to minorities and refugees. This Pi Day, take some time to think about that — but take some space, too.

Michael D. Gordin is the Rosengarten Professor of Modern and Contemporary History at Princeton University. His books include A Well-Ordered Thing: Dmitrii Mendeleev and the Shadow of the Periodic Table and Five Days in August: How World War II Became a Nuclear War (both Princeton). He lives in Princeton, New Jersey. Twitter @GordinMichael