Operation Grapple Burgess and Donald Maclean in 1951. Fearing a resurgence of American isolationism and Britain losing its great power status, the British government restarted its own development effort, now codenamed High Explosive Research. The successful test of an atomic bomb in Operation Hurricane in October 1952 represented an extraordinary scientific and technological achievement. Britain became the world's third nuclear power, reaffirming the country's status as a great power, but hopes that the United States would be sufficiently impressed to restore the Special Relationship were soon dashed. In November 1952, the United States conducted Ivy Mike, the first successful test of a
Atomic clock of using atomic transitions to measure time was suggested by Lord Kelvin in 1879. Magnetic resonance, developed in the 1930s by Isidor Rabi, became the practical method for doing this. In 1945, Rabi first publicly suggested that atomic beam magnetic resonance might be used as the basis of a clock. The first atomic clock was an ammonia absorption line device at 23870.1 MHz built in 1949 at the U.S. National Bureau of Standards (NBS, now NIST). It was less accurate than existing quartz clocks, but served to demonstrate the concept. The first accurate atomic clock, a caesium standard based on