  Einstein's Clock An interesting article on urlLink NYtimes.com What does it mean, Albert Einstein asked in 1905, to say that a train arrives someplace — in Paris, say — at 7 o'clock?
You might not think you need to know something as deep as relativity to answer such a question. But Einstein needed to answer the question to invent his theory of relativity, the breakthrough that wrenched science into a new century and enshrined the equivalence of matter and energy. In his last step, after a decade of pondering the mysteries of light and motion, Einstein concluded that there was no such thing as absolute time, envisioned by scientists since Newton, ticking uniformly through the cosmos. Rather there were only the times measured by individual clocks. To talk about times and measurements at different places, the clocks have to be synchronized, he said. And the way to do that is to flash light signals between them, correcting for the time it takes for the signal to travel from one clock to another. A simple prescription. Yet when Einstein followed it, he found that clocks moving with respect to one another would not run at the same speed. The modern age was born. 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. That is one of the messages of Dr. Galison's new book, "Einstein's Clocks, Poincaré's Maps: Empires of Time," due out in August from W. W. Norton.
Part history, part science, part adventure, part biography, part meditation on the meaning of modernity, Dr. Galison's story takes readers from the patent office to lonely telegraphers sitting in the rain in the Andes, from the coal mines of France to town councils in New England as it circles around the exploits of Einstein and his rival, the French physicist, philosopher and mathematician Henri Poincaré. Read the full article at urlLink NewYork Times Site 
