First Atomic Clock, 1948

In 1948, near this site, Harold Lyons at the National Bureau of Standards developed the first atomic clock, which revolutionized timekeeping by using transitions of the ammonia molecule as its source of frequency. Far more accurate than previous clocks, atomic clocks quickly replaced the Earth's rotational rate as the reference for world time. Atomic clock accuracy made possible many new technologies, including Global Positioning System (GPS).

Washington, District of Columbia · United States