A caesium fountain clock that keeps the United Kingdom’s atomic time is now the most accurate long-term timekeeper in the world, according to a new evaluation of the clock that will be published in the October 2011 issue of the international scientific journal Metrologia by a team of physicists at the National Physical Laboratory (NPL) in the United Kingdom and Penn State University in the United States. An early posting of the paper on the journal’s online site will occur on 26 August 2011.
The clock is one of an elite group of caesium fountain clocks that have been built by the timing labs in Europe, the United States, and Japan as their national “primary frequency standard” for the measurement of time. These national standards are averaged to produce International Atomic Time and Universal Coordinated Time, which are used as time scales worldwide for such critical processes as global communications, satellite navigation and surveying, and time stamping for the computerized transactions of financial and stock markets. The methods used to improve the U.K. clock also can be used to evaluate the caesium fountain clocks of other countries, substantially improving the world’s most accurate methods of keeping time.