The Atomic Bomb was developed during WW2 by scientists working on the top secret Manhattan Project. The United States  with the authorization of President Harry Truman, dropped an atomic bomb on the people of Hiroshima, Japan on August 6, 1945 and one on Nagasaki, Japan on August 9, 1945.

Who invented the Atomic Bomb? The Atomic bomb was invented by scientists working in the WW2 Manhattan Project. Robert Oppenheimer was the scientific director of the Manhattan Project and is referred to as the "father of the atomic bomb"

What is an Atomic Bomb? An Atomic Bomb is an explosive weapon of great destructive power which results from the rapid release of an immense quantity of energy in a chain reaction of nuclear fission, especially of uranium-235 or plutonium-239. The term 'Fission' is given to the process of "splitting" atoms through their bombardment by neutrons.

When was the first test of the Atomic Bomb? The first test of the Atomic Bomb was made during the Manhattan Project on July 16, 1945 at Alamogordo, New Mexico. The first atomic bomb was called "The Gadget", laboratory euphemism for a bomb.

Who dropped the Atomic Bomb in WW2? The WW2 Atomic Bomb was dropped at Hiroshima by Colonel Paul Tibbets in a Boeing B-29 Superfortress bomber that he named 'Enola Gay'. The name given to the Hiroshima bomb was "Little Boy"

The Decision to Drop the Atomic Bomb - Was it the Right Decision?
The momentous decision to drop the Atomic Bomb was made by President Harry Truman. Ever since the Atomic Bombs were dropped on Hiroshima and Nagasaki a debate has raged over whether it was the right decision. Even before the bombs were dropped scientists and politicians hotly debated the issue. The WW2 Potsdam Declaration or the Proclamation dated July 26, 1945 contained an ultimatum stating that, if Japan did not surrender, it would face "prompt and utter destruction". The Japanese did not reply. Those totally opposed to dropping the Atomic Bomb argued that it would indiscriminately kill civilians and that conventional bombing and economic sanctions would force Japan to surrender. Some argued that the Japanese should be warned about the bomb others argued that the only way that Japan would surrender was if the atomic bomb was dropped without warning, and the shock would force the Japanese into surrendering.

What were the effects of the Atomic Bomb? The Effects of the Explosion
The effects of an atomic bomb explosion produces an intense light flash, a sudden wave of heat, followed by a tremendous roar due to the shock wave of the explosion. A ball of fire rises rapidly, followed by a mushroom cloud that extends to heights of 40,000 feet (12,200 metres).

What were the effects of the Atomic Bomb? The Effects on the Ground
The effects of an Atomic Bomb are truly terrifying, much of the surrounding areas of the bomb are vaporized. Most damage caused by an Atomic Bomb comes from the explosive blast. The nuclear blast causes a shock wave of air to radiate outward, producing changes in air pressure that can  crush objects and produce high winds that can knock objects down. When an Atomic bomb is detonated, the blast creates a large crater. Debris from the crater is carried up into the air and made radioactive by the explosion. This deadly material returns to the earth as radioactive fallout. The city streets of Hiroshima and Nagasaki burned bright red, like live charcoal. Roof-tiles and granite stone melted due to the intense heat.

What were the effects of the Atomic Bomb? Black Rain
The Hiroshima and Nagasaki explosions carried particles of uranium and plutonium that escaped fission. Following the explosions, these and other irradiated materials were carried high into the atmosphere and mixed with the heat and thermal currents from the firestorms led to rainfall in the form of "Black Rain". The "Black Rain" was produced by fallout particles were mixed with carbon residue from numerous city fires. Within 30-40 minutes of the bombings, in both Hiroshima and Nagasaki, the deadly “Black rain” fell.

What were the effects of the Atomic Bomb? The Effects on the People
When an atomic bomb explodes, as in Hiroshima and Nagasaki during WW2, people receive two doses of radiation. One dose during the explosion and another from fallout. The rapid release of an immense quantity of energy results in an intense burst of heat that causes skin burns as far as 5 miles from the nuclear blast. The dead were found carbonized. Direct radiation occurs at the time of the nuclear explosion. Intense exposure to radioactive material kills nerve cells and small blood vessels causing seizures, heart failure and immediate death. Damage to the intestinal tract lining causes nausea, bloody vomiting and diarrhea. Radiation sickness destroys the cells in the body including blood cells, reproductive cells and hair cells. Delayed effects can appear months to years after irradiation and include a wide variety of effects involving almost all tissues or organs resulting in cancer, decreased fertility, and genetic mutations.

Facts about Atomic Bomb
The following fact sheet contains interesting facts and information on Atomic Bomb.

The term 'Atomic bomb' was first recorded in 1914 when Science fiction writer H. G. Wells wrote about the idea wrote of using Atomic Bombs in his novel 'The World Set Free'. H. G. Wells also predicted aerial bombardment and an imminent devastating world war in the same book.

The atomic bomb was developed by scientists on the Manhattan Project during WW2. The first test of the A-Bomb was made on July 16, 1945 at Alamogordo, New Mexico.

Scientists working on the Manhattan project took less than 4 years to develop the Atomic Bomb. Most of the work took place in vast facilities in Hanford, Washington, Oak Ridge, Tennessee, and Los Alamos, New Mexico

Two scientists working at Los Alamos, Harry Daghlian and Louis Slotin, died of acute radiation poisoning following accidents during "Tickling the dragon's tail" experiments involving  uranium and plutonium cores at Los Alamos, New Mexico. The two men suffered days of the ravaging effects of radiation sickness before they died.

The term "Tickling the dragon's tail" was a coined by physicist Richard Feynman who said that the dangerous experiments to determine the amount of fissionable material needed for a sustained chain reaction were "like tickling the tail of a sleeping dragon."

Four different design shapes and sizes were made for the Atomic bombs during the Manhattan Project and were given the code names of "The Gadget", "Fat Man", "Thin Man" and "Little Boy". The code names were created by Robert Serber, a US physicist, who worked on the Manhattan Project.

"The Gadget": "Gadget" was the code name given to the first atomic bomb ever detonated at Alamogordo, New Mexico. The term "Gadget" was a laboratory euphemism for a bomb. The "Gadget" was an experimental test version of the implosion system eventually used in "Fat Man".

"Fat Man": The "Fat Man" atomic bomb was short, round and fat and given the nickname for the character of Sydney Greenstreet in the movie called 'The Maltese Falcon'.  "Fat Man" was seen as representing Winston Churchill. The "Fat Boy" atomic bomb was an implosion model plutonium bomb. It was 10.6 feet (3.3 m) long and 5 feet (1.5 m) wide.

"Thin Man": The "Thin Man" was a long, thin shaped Atomic bomb that turned out to be impractical. The name "Thin Man" was taken from the detective novel by Dashiell Hammett called  'The Thin Man' although it was seen as representing President Roosevelt. The "Thin Man" atomic bomb was 17 feet (5.2 m) long, with a 38-inch (97 cm) wide tail, and a 23-inch (58 cm) mid-section. Physicists at the Manhattan Project abandoned the "Thin Man" as the gun-type bomb that used plutonium was found to be impractical. It was replaced by the smaller "Little Boy" bomb.

"Little Boy": The "Little Boy" nuclear bomb was a development of the unsuccessful "Thin Man" atomic bomb. It was a gun-type fission weapon, using uranium rather than plutonium. The "Little Boy" codename was chosen because of its close relationship to the "Thin Man", its "Little Boy". The "Little Boy" atomic bomb was 10 feet (3.0 m) long and 28 inches (71 cm) wide.

Fission: Pure fission weapons were the first nuclear weapons built and the only type ever used in warfare. Fission is the term given to the process of "splitting" atoms through their bombardment by neutrons. The active material is uranium or plutonium. The atomic bombs are explosively assembled into a chain-reacting critical mass by one of two methods - Gun assembly or Implosion.

Gun Assembly: The Gun assembly method used in building an atomic bomb consists of one piece of fissile uranium that is fired at a fissile uranium target at the end of the weapon, achieving critical mass when combined. The method is similar to firing a bullet down a gun barrel, hence the name.

Implosion: The Implosion method used in building an atomic bomb consists of a fissile mass of either Uranium (U-235) or Plutonium (Pu-239) or a combination of both which is surrounded by high explosives that compress the mass, resulting in criticality, a sustained nuclear chain reaction.

Robert Oppenheimer: J. Robert Oppenheimer, director of the Manhattan Project, is often referred to as the "Father of the Atomic Bomb". Following the Trinity test, and the first detonation of a nuclear weapon ("Gadget"), J. Robert Oppenheimer uttered the famous quote "Now I am become Death, the destroyer of worlds."

Pumpkins: Colonel Paul Tibbets and the 393rd Bombardment Squadron begin test drops with dummy bombs called "Pumpkins". The "pumpkins" were painted a distinctive mustard colored and were of the approximate size and weight of the "Fat Man" bomb.

Hiroshima: The first atomic bomb, "Little Boy" was dropped at 08.15am on Hiroshima, a city in Honshu, Japan's main island during WW2 on August 6, 1945. The Atomic Bomb destroyed 76,000 buildings, about 63% of the city. It is estimated that 265,000 people have died due to this atomic bomb, including its radioactive fallout.

Hiroshima: Hiroshima was chosen as the target for the first atomic bomb to be dropped on Japan because it was a large port city with a Japanese army base. Hiroshima had not been damaged much by previous bombings during WW2 and the destruction and devastation inflicted on the city would show the power of the new atomic weapon.

Enola Gay: The Enola Gay was the name was painted on the side of the Boeing B-29 Superfortress bomber that became the first aircraft to drop an atomic bomb. The Enola Gay bomber dropped the atomic bomb, "Little Boy" on the city of Hiroshima. The aircraft was named for Enola Gay Tibbets, the mother of the pilot, Colonel Paul Tibbets.

Nagasaki: The second atomic bomb, "Fat Man" was dropped on Nagasaki, a city in Kyushu, Japan three days later on August 9, 1945. The Atomic Bomb destroyed half of the city. It is estimated that about 150,000 people have died as a result of this bombing including its radioactive fallout. The Nagasaki "Fat Man" bomb was made from plutonium, which was even more powerful than uranium and did not require arming in flight.

Nagasaki: The intended target for the second atomic bomb  was Kokura, but there was too much cloud cover for visual targeting, so the destination of the second atomic bomb was changed to the backup target of Nagasaki

Bockscar: The name 'Bockscar' was given to the B-29 bomber that dropped the second atomic bomb, "Fat Boy", on the Japanese city of Nagasaki.

In 1946 Operation Crossroads began nuclear tests at Bikini Atoll in the Marshall Islands. The "Able" test detonation was on July 1, 1946 and the "Baker" test was detonated on July 25, 1946

The development of the Atomic Bomb led to the Cold War Arms Race which led to the development of the hydrogen bomb and intercontinental ballistic missiles.

Japan is the only country in the world to have suffered from atomic bombings. Japan adopted the "three non-nuclear principles" of not possessing, not manufacturing and not permitting the entry into Japan of nuclear weapons.

To date, over 2,000 nuclear tests have been carried out at different locations all over the world.

The 1963 Partial Test Ban Treaty banned nuclear tests in the atmosphere, underwater and in space, but not underground. Neither France nor China signed the PTBT.

The 1996 Comprehensive Nuclear-Test-Ban Treaty (CTBT) by which countries agree to ban all nuclear explosions in all environments. It was not signed by India, North Korea or Pakistan.