US starts atomic clock accurate to one second per 300 million years

Some good news for people who are sticklers for punctuality: the United States' National Institute of Standards and Technology has a new atomic clock that is not supposed to gain or lose a second in roughly 300 million years.

The new clock - called NIST F-2 - is the nation's civilian time standard; the US Naval Observatory maintains military time.

Launched on Thursday at the institute's centre, in Boulder, in the state of Colorado, NIST F-2 is about three times more accurate than the old one, NIST F-1. The institute plans to operate both for a while and use comparisons to help improve them.

Banks, computer networks and others use the atomic clock to synchronise their own clocks.

Each day the institute's radio broadcasts are used to update about 50million timekeepers, while its internet service attracts about eight billion automated synchronisation requests.

"Nothing here is going to change the way we live tomorrow, in terms of having a three-times-more-accurate clock," says physicist Steven Jefferts, lead designer of the new clock. "But these technologies keep getting adopted for use in our society, so we have to keep inventing things to make them work better."

Both clocks use caesium atoms to determine the exact length of a second. They measure the frequency of a particular transition in the caesium atom - more than 9.1 billion vibrations per second to define one second.

One key difference is that the old clock operates at about 26.6degrees Celsius, while the atoms in the new clock are kept at about minus 193 degrees; the cooling significantly lowers the background radiation and helps to reduce some tiny measurement errors in the old clock.