Time is Money

A second atomic clock officially started ticking at the National Institute of Standards and Technology (NIST) in April, helping to set a more precise standard for U.S. civilian time. Initial tests by the Gaithersburg, Md.-based agency indicate that the device is the world’s most accurate timepiece.

Timekeeping devices have long used a swinging pendulum or an oscillating crystal to mark off increments of time. Inside of NIST’s two atomic clocks, the back and forth motion of a pendulum is replaced by the vibrations of atoms within a chamber of cesium gas. Every time the atoms reach a certain frequency — 9,192,631,770 cycles per second, to be exact — the clocks generate an electronic tick.

This oscillation is quite stable over time. NIST-F1, built in 1999, keeps time to within one second every 100 million years. The new NIST-F2 is even better, gaining or losing a second in 300 million years.

Timekeeping has steadily improved over the centuries, driven by an interconnected world’s need to stay synchronized over long distances. In the 19th century, the expansion of railroads across the United States created the need for a uniform time standard for all trains to follow. In response, astronomical stations distributed time observations via telegraph. In the 21st century, global positioning satellites with atomic clocks send time signals that calibrate navigational equipment on boats, airplanes, and automobiles.

NIST broadcasts time signals via shortwave radio 24 hours a day, seven days a week. These signals keep cellphone and computer networks running smoothly, synchronizing pulses of information as they are transmitted and received between two points. They are also used by power companies to ensure that electricity is transmitted at the proper frequency.

Steven Jefferts, lead designer of NIST’s new clock, reflected upon this technological progress when his agency announced the start of the clock’s operation in Boulder, Colo. “If we’ve learned anything in the last 60 years of building atomic clocks, we’ve learned that every time we build a better clock, somebody comes up with a use for it that you couldn’t have foreseen.”