istoryworld
Events relating to physics
Albert Einstein formulates the law of photochemical equivalence, a fundamental principle of chemical reactions induced by light
Lawrence Bragg and his father, William, together develop X-ray crystallography, based on the diffraction patterns of crystals
The Danish physicist Niels Bohr uses quantum theory as a key to understanding the structure of the atom
English physicist Henry Moseley proposes that the atomic number of an element is a physical reality, thus laying the basis for the modern periodic table
Einstein submits a paper, The field equations of gravitation, containing the sums required to explain the general theory of relativity
23-year-old German physicist Werner Heisenberg publishes his ground-breaking theory of quantum mechanics
Austrian physicist Wolfgang Pauli formulates his exclusion principle, stating that no two electrons in an atom can have the same four quantum numbers
Werner Heisenberg publishes his Uncertainty Principle, declaring that it is impossible to define precisely the position and momentum of a sub-atomic particle
Wolfgang Pauli announces his mathematical proof of the existence of the particle subsequently known as the neutrino
British theoretical physicist Paul Dirac predicts the existence of an anti-particle of the electron, first observed two years later and named the positron
John Cockcroft and Ernest Walton are the first to split an atom, by bombarding it with accelerated protons
British physicist James Chadwick shows that the behaviour of subatomic particles can be explained by the existence of neutrons, or particles with no electrical charge
Frédéric and Irène Joliot-Curie discover artificial radioactivity
German physicists, led by Otto Hahn, announce their discovery of nuclear fission
German-born US physicist Albert Einstein writes to President Roosevelt, warning of the potential of an atomic bomb
Radar masts along the coasts of Britain give early warning of German air attacks
US physicist J. Robert Oppenheimer is appointed director of the Manhattan Project to develop a nuclear weapon
Enrico Fermi and his team in Chicago achieve the first nuclear chain reaction
US scientists succeed in exploding an atom bomb at Alamogordo, a test site in the New Mexican desert
An atom bomb is dropped on Hiroshima, destroying four square miles of the city and killing 80,000 people
The first of about 20 US tests of atomic and hydrogen bombs is carried out on Bikini Atoll, in the Pacific
Hungarian-born British engineer Dennis Gabor creates the first three-dimensional image from reflected light, subsequently known as a hologram
The first transistor is produced in the Bell Laboratories in Murray Hill, New Jersey
The first Soviet atomic bomb, called by the Americans Joe One, is successfully tested in Kazakhstan
In response to the Soviet atom bomb, President Truman announces a crash programme to develop a hydrogen bomb
