It was written by Lee Larson. The motivation for this month's ramblings came from a conversation I had with an astronomer a few weeks back. Her work involves analyzing data from several radio telescopes in order to patiently tease out subtle differences between their signals. Since these telescopes are thousands of miles apart, the time stamp telling exactly when the data was received is almost as important as the data itself. Not just any clock can time stamp such data.
Differences measured in millionths of a second are important.
They use atomic clocks, which measure time based on the precise tick of cesium atoms, and are accurate to within several millionths of a second per year. They keep time accurately to within a few billionths of a second per year. One of NIST's chief responsibilities is to let everybody else know what time it is. As technology has changed, they've added many ways for us to set our clocks. Any shortwave radio listener can tell you about one of the first methods they used.