Trident (UK nuclear programme) Agreement merged with the American Manhattan Project to create a combined American, British, and Canadian project. The British government expected that the United States would continue to share nuclear technology, which it regarded as a joint discovery, but the United States Atomic Energy Act of 1946 (McMahon Act) ended technical co-operation. Fearing a resurgence of United States isolationism, and Britain losing its great power status, the British government resumed its own development effort. The first British atomic bomb was tested in Operation Hurricane on 3 October 1952. The subsequent British development of the hydrogen bomb, and a fortuitous international relations
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