Cesium beam clocks (left) and hydrogen masers are types of atomic clocks used by the National Institute of Standards and Technology (NIST) to determine official U.S. time.
J. Sherman, R. Jacobson/NIST
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J. Sherman, R. Jacobson/NIST
The US government calculates the country's income official time using more than a dozen atomic clocks at a federal facility northwest of Denver.
But when destructive storm When the power went out at the National Institute of Standards and Technology (NIST) laboratory in Boulder on Wednesday, and the subsequent backup generator failed, time slowed down a bit.
The error “caused NIST UTC [universal coordinated time] 4.8 microseconds slower than it should have been,” NIST spokeswoman Rebecca Jacobson said in an email.
That's just under 5 millionths of a second.
To understand how brief this moment is, Jacobson noted that it takes a person about 350,000 microseconds to blink.
Since 2007Official US time is determined by the Secretary of Commerce, who oversees NIST along with the US Navy. The national time standard is known as NIST UTC. (Somewhat confusingly, UTC itself is a separate global time standard to which the US and other countries contribute measurements.)
NIST currently calculates the standard using a weighted average of the readings from 16 atomic clocks located throughout its Boulder campus. Atomic clocks, including hydrogen masers and cesium beam clocks, rely on the natural resonant frequencies of atoms to tell time with extremely high precision.
All atomic clocks continued to tick even after last week's blackout, thanks to battery backup systems, according to NIST research physicist Jeff Sherman. It was not possible to establish a connection between some of the clocks and NIST's measurement and distribution systems, he said.
Some critical operations personnel still on site after the severe weather were able to restore backup power by activating a diesel generator the team had been keeping on standby, Sherman said.
As for whether the 4.8 microsecond “drift” had any effect, Sherman said it was up to the user. “It might be a little silly to say that four microseconds is both a lot and a little.”
The drift will likely be too minor to matter to the general public, but it could have larger implications for applications involving critical infrastructure, telecommunications, GPS signals and more, Sherman said. (NIST said it was providing “high-end” users with access to other timekeeping networks and notified them of the outages.)
By Saturday evening, power had been restored to the NIST Boulder facility and crews were working to assess the damage and correct the 4.8 microsecond drift in a timely manner.
