A mushroom cloud rises from a nuclear weapon test during Operation TUMBLER-SNAPPER. Over two thousand Marines witnessed the event, which was conducted in 1952 at the Nevada Proving Ground.
WASHINGTON, DC - JANUARY 29: (L-R) National Counterterrorism Center Director Matthew Olsen, FBI Director James Comey, Director of National Intelligence James Clapper, CIA Director John Brennan, Defense Intelligence Agency Director Lt. Gen. Michael Flynn testify during a hearing before Senate (Select) Intelligence Committee January 29, 2014 on Capitol Hill in Washington, DC. The committee held a hearing on "Current and Projected National Security Threats Against the United States." (Photo by Alex Wong/Getty Images)