ATOMIC CLOCK

Otago Daily Times, Issue 27510, 3 October 1950, Page 5

ATOMIC CLOCK

New Super-accurate Timepiece

RESEARCH IN AMERICA WASHINGTON, Rec. 8 p.m. Oct. 1. The National Bureau of Standards announced today that scientists were working on three improved models of its “atomic clock,” and hoped to develop a timepiece that would gain or lose less than one second in 300 years. It is believed that super-accurate clocks would be of tremendous value in many fields of research and engineering, and eventually mig'hit supplant the astronomical standard of measurement based on the earth’s rotation.

The bureau first announced the davelopment of an atomic clock on January 1, 1949. Essentially it was a clock regulated by the frequency of radio waves from a quartz crystal transmitter. The clock was made “ atomic ” and super-accurate by a special attachment which automatically corrected the timing frequency drifts of the quartz crystal transmitter by comparing its output with the vibration of atoms in a long, hollow tube filled with ammonia. The gas vibration of ammonia atoms is absolutely constant, but some margin of error inevitably creeps in through the complex comparison mechanism. The first clock was accurate to one part in 20,000,000. The bureau said the best of the new models might be accurate to one part in 10.0(H),000,000. The bureau said the model would employ a beam of cesium atoms instead of ammonia gas. Cesium atoms had a much sharper “resonance absorption ” point than ammonia gas and would in effect be much more critical of the accuracy of the radio frequency , being compared. A