When the nuclear bomb known as “Little Boy” detonated 1,500 feet above Hiroshima at 8:15 a.m., Aug. 9, 1945, it exploded with the force of 15,000 tons of TNT.

This was Trinity — the world’s first nuclear explosion, marking the moment humankind crossed into the atomic age.Part of The Manhattan Project led by J Robert Oppenheimer, Trinity was a codename ...