In 1957, the United States conducted its first underground nuclear test, known as Rainier, at the Nevada Test Site. The device was detonated inside a carved tunnel deep within the rock, marking a major shift from open-air tests to underground experiments that produced far less radioactive fallout. The explosion created a powerful seismic wave that scientists used to study how nuclear blasts behave beneath the earth. via: NNSANevada yt | History In Pictures