Los Angeles Times
: The official US atomic clock, which has been NIST-F1 since 1999, is about to be upgraded to NIST-F2, which will be three times as accurate. Both measure the number of oscillations in a cesium atom’s resonant frequency. But while NIST-F1’s vertical flight tube is kept at room temperature, that of NIST-F2 is chilled to 80 kelvin (−316 °F), which reduces background radiation and measurement errors. If both clocks were to run for 100 million years, NIST-F1 would lose just one second, and NIST-F2, just 1/3 of a second. Because the technologies used in such systems as telecommunications, the electric power grid, and GPS are requiring ever more accurate time keeping, even newer clocks are being developed that use other types of atoms.