Nuclear Testing Timeline

• 1895: Wilhelm Röntgen of Germany, while conducting experiments with cathode rays, accidentally discovers a new and different kind of ray. These rays were so mysterious that Roentgen named them “x-rays.” He received the first Nobel Prize in Physics in 1901 for this discovery.
• 1896: French physicist Antoine Henri Becquerel’s experiments leads to the discovery of radioactivity. He observed that the element uranium can blacken a photographic plate, even though separated from it by glass or black paper. He also observed that the rays that produce the darkening are capable of discharging an electroscope, indicating that the rays possess an electric charge.
• 1897: J. J. Thomson of Britain discovers the electron, while also studying cathode rays. He received the Nobel Prize in Physics in 1906 for this discovery.
• 1899: Ernest Rutherford discovers two kinds of rays emitting from radium. The first he calls alpha rays; the more penetrating rays he calls beta rays.
• 1900: Frederick Soddy observes spontaneous disintegration of radioactive elements into variants he calls “isotopes.”
• 1902: Ernest Rutherford and Soddy publish theory of radioactive decay.
• 1903: Becquerel shares Nobel Prize for Physics with Pierre and Marie Curie for 1896 discovery of natural radioactivity.
• 1904: Rutherford discovers that alpha rays are heavy positively charged particles. In 1908, he is awarded a Nobel Prize in Chemistry for his work.
  J. J. Thomson proposes the “plum-pudding” model of the atom. In it the atom is envisioned as electrons surrounded by a soup of positive charge, like plums surrounded by pudding.
• 1905: Albert Einstein publishes the special theory of relativity regarding convertibility of matter and energy (E=mc²).
• 1911: The “plum-pudding” is disproved by the gold foil experiment by Ernest Rutherford, when he discovered the nucleus of the atom.
  Marie Curie receives a second Nobel Prize, this time in Chemistry, for the isolation of radium and polonium and for her investigation of their chemical properties.
• 1913: Niels Bohr publishes theory of atomic structure, combining nuclear theory with quantum theory.
• 1915: Albert Einstein publishes the general theory of relativity. The theory proposes that gravity, as well as motion, can affect the intervals of time and of space.
• June, 1919: Rutherford bombards nitrogen gas with alpha particles and obtains atoms of an oxygen isotope and protons. This transmutation of nitrogen into oxygen was the first artificially induced nuclear reaction.
• June, 1920: Rutherford speculates on the existence of the neutron at a lecture to the Royal Society of London.
• 1925: Werner Heisenberg, Max Born and later Erwin Schrödinger formulate quantum mechanics. Heisenberg is awarded the Nobel Prize in Physics in 1932 for the creation of quantum mechanics.
• 1927: Werner Heisenberg states the uncertainty principle, which states that it is not possible to simultaneously determine the position and momentum of a particle.
• 1929: Ernest O. Lawrence conceives idea for the first cyclotron, a device that greatly increased the speed with which protons could be hurled at atomic nuclei. He was awarded the 1939 Nobel Prize in Physics for the invention and development of the cyclotron and for results obtained with it.
  John Crockcroft and E. T. S. Walton develop a high-voltage apparatus (“linear accelerator”) for accelerating protons. With this they study nuclear reactions (atomic transmutation) and are awarded the 1951 Nobel Prize in Physics.
• November, 1931: Harold Urey discovers deuterium, an isotope of hydrogen that contains one proton and one neutron.
• February, 1932: James Chadwick discovers the neutron.
• April, 1933: Max Born, James Franck and many other scientists are compelled to leave their posts at German universities because of their “Jewish physics.”
• October, 1933: Leo Szilard recollects, “It occurred to me in October, 1933 that a chain reaction might be set up if an element could be found that would emit two neutrons when it swallowed one neutron.” This idea became a classified British patent in 1935 before fission was discovered.
• 1934: Frédéric and Irène Joliot-Curie discover artificial radioactivity.
  Enrico Fermi irradiates uranium with neutrons. He believes he has produced the first transuranic element, but unknowingly achieves the world’s first nuclear fission.
• December, 1938: Fermi receives the Nobel Prize in Physics for the discovery of transuranic elements (actually fission of uranium) and departs for the United States.
• December 22, 1938: Otto Hahn sends a paper to Lise Meitner containing experimental results that are interpreted by Meitner and nephew Otto Frisch as nuclear fission.
• January 6, 1939: Hahn and his assistant Fritz Strassmann publish their results.
• February 11, 1939: Meitner and Frisch publish a theoretical interpretation of the Hahn-Strassmann results as nuclear fission.
• January to May, 1939: Many experiments on uranium fission are conducted by scientists in laboratories around the world.
• August 2, 1939: Szilard, Eugene Wigner, and Edward Teller obtain a letter from Einstein on the possibility of a uranium weapon; President Roosevelt receives the letter on October 11, 1939 from Alexander Sachs, who was an unofficial adviser to the President.
  Hans Bethe recognizes that the fusion of hydrogen nuclei to form deuterium releases energy. He suggests that much of the energy output of the Sun results from fusion reactions. He would win the 1967 Nobel Prize in Physics for this effort.

The Trinity test near Socorro, New Mexico, was the first-ever test of a nuclear weapon (yield of around 20 kilotons).

The nuclear weapon (nicknamed ‘Little Boy’) dropped from a United States Army Air Force Boeing B-29 Superfortress bomber (the ‘Enola Gay’) and detonated over Hiroshima, Japan with an energy yield equivalent to that of 15,000 tons of TNT.

The first atomic bomb ever used in warfare was dropped by parachute and exploded 580m (1,900 ft) above the ground. Between 60,000 and 80,000 people were killed instantly. The heat from the bomb was so intense that some people simply vanished in the explosion. Many more died of the long-term effects of radiation sickness. The final death toll was calculated at 135,000. As well as residents of Hiroshima, the victims included Koreans who had been forced to come to Japan as labourers, and American prisoners-of-war who were imprisoned in Hiroshima.

The blast destroyed more than ten square kilometres (six square miles) of the city. And the intense heat of the explosion then created many fires, which consumed Hiroshima and lasted for three days, trapping and killing many of the survivors of the initial blast. Thousands of people were made homeless and fled the devastated city.

Hiroshima was chosen because it had not been targeted during the US Air Force’s conventional bombing raids on Japan, and was therefore regarded as being a suitable place to test the effects of an atomic bomb. It was also an important military base. The Allies feared that any conventional attempt to invade the Japanese home islands would result in enormous casualties, and the bomb was seen as a way of bringing the war against Japan to a swift conclusion. In addition, it may also have been a way of demonstrating American military superiority over the Soviet Union.

The nuclear weapon (nicknamed ‘Fat Man’) dropped from a United States Army Air Force Boeing B-29 Superfortress bomber (the ‘Bockscar’) and detonated over Nagasaki, Japan with an energy yield equivalent to that of 21,000 tons of TNT.

The original target was Kokura, but this was obscured by cloud so the bomb was dropped on nearby Nagasaki, an important port. About 40,000 people were killed instantly and a third of the city was destroyed. The final death toll was calculated as at least 50,000. Some sources report death tolls as high as 80,000 by the end of 1945.

Among those in the plane that dropped the bomb on Nagasaki was the British pilot Leonard Cheshire. He later recalled the cloud caused by the atomic blast in Martin Gilbert’s Second World War:

The Operation Crossroads series in July 1946, at Bikini Atoll in the Marshall Islands, was the first postwar test series and one of the largest military operations in U.S. history.