is improving with age. Scientists at the National Institute of Standards and Technology report in the October issue of the journal Metrologia that the accuracy of the NIST-F1 atomic clock has improved by more that a factor of two since it was first used as a national standard in 1999. If run continuously for 60 million years, they report, it would not gain or lose a single second. The enhancement results mainly from improved lasers and components, a larger volume for the containment of the cesium atoms and greater control over magnetic fields used in the fountain clock.