This is the only surviving color photograph of the Trinity test, the first explosion of an atomic bomb. The device was detonated in a largely unpopulated area of New Mexico, the White Sands Proving Grounds (now the White Sands Missile Range).

Photograph by Jack Aeby, courtesy Department of Energy
  • On July 16, 1945, the first atomic bomb, codenamed Trinity, was successfully tested by the U.S. Army. The bomb detonated at 5:29 a.m. in New Mexico’s White Sands Proving Grounds (now White Sands Missile Range). Scientists moved themselves 9,144 meters (10,000 yards) away from the bomb, and hit the switch. Within seconds they witnessed a mushroom cloud that extended 12,192 meters (40,000 feet) into the air. The explosion produced the same amount of energy as 15,000 to 20,000 tons of TNT.

    An atomic bomb is an explosive weapon powered by nuclear fission—the tremendous release of energy created as the nucleus of an atom splits. Uranium and plutonium are the most common nuclear fuel, and Trinity was a plutonium bomb.

    In July 1945, the United States was still locked in the bloody battles of the Pacific Theater of World War II. The Trinity test was so successful that the U.S. used a virtually identical weapon on Nagasaki, Japan, less than a month later. The nuclear bombing of Japan is largely credited with ending the war.

  • Term Part of Speech Definition Encyclopedic Entry
    atomic bomb Noun

    explosive device that draws energy from the interaction of atomic nuclei. Also called an atom bomb, a-bomb, or nuclear bomb.

    detonate Verb

    to cause something to explode.

    element Noun

    chemical that cannot be separated into simpler substances.

    energy Noun

    capacity to do work.

    nucleus Noun

    head of a comet, mostly composed of frozen gases and solid particles of ice.

    Pacific theater Noun

    military operations taking place in the Pacific Ocean. The Pacific theater usually refers to actions during World War II.

    plutonium Noun

    chemical element with the symbol Pu. Used to make nuclear weapons and as a power source.

    tremendous Adjective

    very large or important.

    uranium Noun

    chemical element with the symbol U. Fuel used to produce nuclear energy.

    virtually Adverb

    almost or nearly.

    weapon Noun

    tool to hurt or combat an opponent.

    World War II Noun

    (1939-1945) armed conflict between the Allies (represented by the United States, the United Kingdom, and the Soviet Union) and the Axis (represented by Germany, Italy, and Japan.)

    World War II Noun

    (1939-1945) armed conflict between the Allies (represented by the United States, the United Kingdom, and the Soviet Union) and the Axis (represented by Germany, Italy, and Japan.)