British and U.S. scientists have confirmed that an atomic clock at the National Physical Laboratory (NPL) near London is the most accurate long-term t

The NPL-CsF2 is a cesium fountain clock that's used as a standard for International Atomic Time and Universal Coordinated Time.

The machine is apparently accurate to within two 10 million billionths of a second. Not bad, I guess.

The NPL's Krzysztof Szymaniec joined scientists from Pennsylvania State University in evaluating the clock. The team published its results in the journal Metrologia.

The analysis concludes that the clock will lose only a billionth of a second every two months, and represents an unprecedented accuracy. Cesium clocks are usually expected to lose or gain a second over tens of millions of years.

"Together with other improvements of the cesium fountain, these models and numerical calculations have improved the accuracy of the U.K.'s cesium fountain clock, NPL-CsF2, by reducing the uncertainty to 2.3 × 10^-16--the lowest value for any primary national standard so far," Szymaniec was quoted as saying by the NPL.

In the U.S., the National Institute of Standards and Technology operates the NIST-F1 cesium fountain clock, which as of summer 2010 had an uncertainty of 3 x 10^-16, meaning it would take more than 100 million years to lose or gain a second.

That will be billions of years before the sun dies, taking the Earth with it, so I expect an update on this from a future blogger.

(Credit: National Physical Laboratory)