Just 3 weeks before the atomic bomb
attacks on Japan, the first nuclear explosion in history
had taken place in secrecy in the desert of New Mexico,
USA, when scientists working for the Manhattan Project
tested the experimental nuclear bomb codenamed
Trinity. That test ushered in an era of atmospheric
nuclear testing by the USA, the USSR, the UK, China,
and France that continued at sites around the world
until 1980 (fi gure).