US Time Now Set by New Atomic Clock

Time in the US is now being kept by a new atomic clock, the US Department of Commerce's National Institute of Standards and Technology (NIST) said Thursday. The new cesium clock is so accurate it isn't meant to gain or lose a second in the next 300 million years.

The atomic clock will serve as the new standard for US civilian timekeeping and frequency standard. The new clock dubbed NIST-F2, will operate in tandem with its predecessor, NIST-F1, which has been setting the standard for US civilian time since 1999.

Both of the clocks keep time using a "fountain" of cesium atoms to determine the exact length of a second.

It took more than a decade to develop the NIST-F2, and its record of time was used in by the International Bureau of Weights and Measures (BIPM) to establish Coordinated Universal Time (UTC).

According to the BIPM, the new US atomic clock is now the most accurate time standard.

"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," NIST physicist Steven Jefferts, lead designer of NIST-F2, said in a statement.

Cesium fountain clocks measure the frequency of a specific transition in the cesium atom - clocked at 9,192,631,770 vibrations per second.

This standard is used to define the amount of time in one second.

The key difference in the new clock and its predecessor is the original F1 clock operates near room temperature and the F2 operates at a much colder minus 316 degrees Fahrenheit (minus 193 Celsius).

The colder operating temperate reduces some of the very small measurement errors that must be corrected for in the F1 clock.

A report on the new clock appears in the journal Metrologia.