THREE QUARTERS OF A CENTURY AGO THIS SUMMER, on July 16, August 6, August 9, and September 2, nuclear weapons altered our civilization forever. On July 16, in New Mexico, the Trinity plutonium bomb detonated with the energy equivalent of 22 kilotons (22,000 metric tons) of TNT, sending a mushroom cloud 39,000 feet into the atmosphere, left a crater 76 meters wide filled with radioactive glass called trinitite (melted quartz grained sand), and could be heard as far away as El Paso, Texas. On August 6, the Little Boy gun-type uranium-235 bomb exploded with an energy equivalent of 16-18 kilotons of TNT, flattening 69 percent of Hiroshima’s buildings and killing an estimated 80,000 people and injuring another 70,000. On August 9, the Fat Man plutonium implosion-type bomb with the energy equivalence of 19-23 kilotons of TNT was dropped and leveled around 44 percent of Nagasaki, killing an estimated 35,000 to 40,000 people and severely wounding another 60,000.1
As documented in the memo below dated August 10, 1945, if the Japanese had not surrendered, the head of the Manhattan Project, Major General Leslie R. Groves, had another Fat Man-type plutonium implosion bomb ready to go after August 24 that would have likely killed another 50,000 to 100,000 people.2 And had the Japanese military hardliners had their way to continue the war into the fall, Groves had three more bombs readied for September and another three for October. So President Harry Truman was not exaggerating when he threatened Japan with “a rain of ruin from the air, the like of which has never been seen on this Earth.” Truman did agonize about dropping more nukes on Japan, troubled as he was by the thought of more innocents and non-combatants being killed, and he wrestled away from the military the authority to do so (note Groves’ handwritten addendum to his memo that “It is not to be released on Japan without express authority from the President” Ever since U.S. presidents have had sole authority to use nuclear weapons). This was unnecessary, however, as on August 15 Emperor Hirohito, against the wishes of some of Japan’s military leaders, announced on the radio that Japan would capitulate. On September 2, they signed the surrender documents in Tokyo Bay, ending the Second World War.3
On July 16, the Trinity plutonium bomb detonated with the energy equivalent of 22 kilotons (22,000 metric tons) of TNT. This is the explosion at 16 milliseconds.