NIST gets closer to keeping perfect time

The National Institute of Standards and Technology last week officially launched a new atomic clock that scientists are calling the most accurate time measurement device in the world.

Called NIST-F2, the new clock is now the official source of time for the United States, said Tom O’Brian, chief of the Time and Frequency Division at NIST. The clock is so accurate that if it ran continuously for 300 million years, it would not stray from perfect time by one second, O’Brian said, speaking to reporters April 3.

NIST-F2 is three times more accurate than its predecessor, NIST-F1, which has served as the standard since 1999.

The ultra precision of atomic clocks has become a critical foundation of modern technologies, from telecommunications to global positioning systems and the electric power grid.


Modern telecommunications and computer network systems, as well as the electric power grid “require synchronization to about 1 millionth of a second per day,” O’Brian said. “And the GPS system that’s used to navigate airlines and our personal cars requires synchronization to about 1 billionth of a second per day. And now, most people are carrying around GPS with them all the time in smartphones and tablets.”

The NIST-F2 atomic clock uses infrared laser beams to cool millions of cesium atoms to temperatures near absolute zero. The cooling allows scientists to slow the atoms down significantly and precisely measure their natural vibrations.

“And that means that roughly speaking, if you could make either one of them run for 100 million years, NIST F-1 would lose a second and NIST F-2 might lose a third of a second in that period,” said Steve Jefferts, NIST project leader for primary frequency standards.

The first atomic clocks were invented in 1950, when NIST was known as the National Bureau of Standards. “Since then … we’ve had a factor of improvement of more than a million, with improvements seeming to accelerate,” O’Brian said.

But even as NIST celebrates the new technical achievements of NIST-F2, scientists are hard at work on newer, more accurate clocks. The next generation of atomic clocks, known as Optical Clocks “are already more precise than NIST-F2,” O’Brian said. “Now these are research clocks, they’re not anywhere near ready to serve as official timekeeping devices yet, but they will be in the future.”


It won’t be long, according to Jefferts, before scientists are “redefining the second” with the help of optical clocks.

“And when we do that we need to be able to make the transition from the definition of cesium, from the use of cesium as the definition of the second, to the use of some optical standard that hasn’t been determined yet,” he said.

How The NIST-F2 Atomic Clock Works

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