Down to the Picosecond

摘要

On any given day, the Navy's newest and most precise clocks might gain or lose 50 picoseconds. At that rate, the clocks would creep one second ahead or lag one second behind every 300 million years, said Steven Peil, a Navy physicist who helped develop the exotic chronometers. To most people, that wouldn't matter. A picosecond - a trillionth of a second - and even the much larger nanosecond - a billionth of a second - is too brief to be noticed. Except at the U.S. Naval Observatory. There, "we actually care about how many picoseconds it loses per day," Peil said. That's because extremely precise timing has become extremely important to the U.S. military, and the Navy is the military's official timekeeper. It has been since 1854.