Number 127 (Story #2), May 5, 1993 by Phillip F. Schewe and Ben Stein NIST-7, THE WORLD'S BEST CLOCK, , will drift by only 1 second every 3 million years. The new device essentially defines the second as being 9,192,631,770 cycles of microwave radiation from an atomic transition in cesium-133. Built at the National Institute of Standards and Technology, the new clock is 10 times better than the previous standard, a device called NBS-6. (Science News, 1 May 1993.)