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 timekeeper in the world, the NPL said.
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