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.

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.)

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