From 1942, US scientists worked in secret to create a bomb so powerful it could end the war. The bomb’s explosive power would come through the release of energy stored within atoms. Fear that the Germans would master the technology first drove the scientists on.
American scientist Robert Oppenheimer, leader of the Manhattan Project, views the remains of the steel tower, which melted in the intense heat where the first atomic bomb was tested.
In the early 20th century, the great physicist Albert Einstein (1879–1955) showed that matter could be turned into energy. To do this, scientists had to split the basic building blocks of matter—atoms. At the center of every atom is a cluster of particles called the nucleus. Splitting the nucleus could release tremendous amounts of energy—known as nuclear energy.
Thousands of people were involved in the “Manhattan Project” to build the bomb. On July 16, 1945, after three years’ research, they produced the world’s first nuclear explosion. It was equivalent to 20,900 tons (19,000 metric tons) of TNT and it threw into the sky a mushroom-shaped cloud of vapor and debris.
A mushroom cloud towers more than 3.7 miles (six kilometers) above Nagasaki following the nuclear attack by the United States. The heat on the ground reached about 5,400 degrees Fahrenheit (3,000 degrees Celsius).
Soon afterward, the United States used nuclear bombs for the first time as weapons of war. Victory was imminent in the United States’ war against Japan, but the Japanese refused to surrender, and an invasion looked like the only solution. This was likely to cost the lives of hundreds of thousands of soldiers and civilians.
The US government decided instead to drop nuclear bombs on two Japanese cities to convince the Japanese to surrender. “Little Boy” was dropped on Hiroshima on August 6, 1945, leveling two-thirds of the city and killing about 200,000. Three days later, “Fat Man” was dropped on Nagasaki. Japan surrendered on September 2, ending World War II.
