WASHINGTON -- One hundred years ago a minor Swiss civil servant, having traveled home in a streetcar from his job in the Bern patent office, wondered: What would the city's clock tower look like if observed from a streetcar racing away from the tower at the speed of light? The clock, he decided, would appear stopped because light could not catch up to the streetcar, but his own watch would tick normally.
``A storm broke loose in my mind,'' Albert Einstein later remembered. He produced five papers in 1905 and for physicists, the world has never been the same. For lay people, it has never felt the same.
In his book ``Einstein's Cosmos,'' Michio Kaku, professor of theoretical physics at the City University of New York, makes Einstein's genius seem akin to a poet's sensibility. Einstein, says Kaku, was able to ``see everything in terms of physical pictures'' -- to see ``the laws of physics as clear as simple images.''
Hitherto, space and time were assumed to be absolutes. They still can be for our everyday business, because we and the objects we deal with do not move at the speed of light. But since Einstein's postulate of relativity, measurements of space and time are thought to be relative to speed.
One implication of Einstein's theories did have thunderous practical implications: matter and energy are interchangeable, and the mass of an object increases the faster it moves. In the most famous equation in the history of science, energy equals mass multiplied by the speed of light squared. A wee bit of matter can be converted into a city-leveling amount of energy.
In the 1920s, while people were enjoying being told that space is warped and it pushes things down (that is the real ``force'' of gravity), Einstein became an international celebrity of a sort not seen before or since. Selfridges department store in London pasted the six pages of an Einstein paper on a plate glass window for passersby to read. Charlie Chaplin said to him, ``The people applaud me because everyone understands me, and they applaud you because no one understands you.''