Measures for Progress: A History of the National Bureau of Standards

476 THE NEW WORLD OF SCIENCE (1946-51)
Dr. Condon and Dr. Harold Lyons with the first atomic beam clock. It operated with
an ammonia-regulated quartz crystal and ran with a constancy of one part in 20
million.
The Bureau atomic clock program sought to provide a spectroscopic standard
capable of being used as a new atomic standard of time and frequency to replace
the mean solar day and so change the arbitrary units of time to atomic ones. With
such a clock, new precise values might be found for the velocity of light; new
measurements of the rotation of the earth would provide a new tool for geophysicists;
and new measurements of the mean sidereal year might test whether Newtonian and
atomic time are the same, yielding important results for the theory of relativity and
for cosmology.
The new microwave measurement technique, by overcoming the limi-
tations of conventional optical and infrared equipment, also promised to
extend spectroscopic analysis methods to high polymer research, that is, to
the investigation of organic substances such as paper, leather, and plastics
which are made up of very large molecules.'32 An immediate and dramatic
application of the microwave technique, however, was in the Bureau's con-
struction of an atomic clock.
Annual Report 1948, pp. xiv, 249.