|1900 AD||Max Planck states his radiation law and Planck's constant.|
|1902||Rutherford and Frederick Soddy discover the law of radioactive decay.|
|1903||Rutherford and Soddy publish work on radioactivity as the transformation of atoms.|
|1905||Albert Einstein completes his theory of special relativity.
Einstein explains the photoelectric effect.
Einstein explains Brownian motion as due to molecular collisions.
|1906||Hermann Walther Nernst presents a formulation of the third law of thermodynamics.|
|1908||Hans Geiger and Rutherford invent the Geiger counter.|
|1909||Rutherford and Royds demonstrate that alpha particles are doubly ionized helium atoms.|
|1911||(to 1913) Soddy, Russell, and Kazimir Fajans recognize the existence
of isotopes among radioactive elements.
Rutherford proposes nuclear model of the atom.
|1913||Henry Gwyn Moseley shows that nuclear charge is the real basis
for numbering the elements.
Robert Millikan measures the fundamental unit of charge.
|1915||Einstein completes his theory of general relativity.|
|1916||Lewis and Irving Langmuir formulate an electron shell model of
Arnold Sommerfeld proposes elliptical orbits for electrons in atoms.
Niels Bohr proposes correspondence principle.
|1919||Rutherford achieves the first artificial disintegration of a nucleus -- the transmutation of the nitrogen nucleus by alpha particle bombardment.|
|1924||Louis Victor De Broglie advances
the wave theory of material particles.
Wolfgang Pauli proposes the exclusion principle.
|1926||Erwin Schrödinger states his nonrelativistic quantum wave equation.|
|1927||Clinton Joseph Davission, Lester Germer, and George Thomson confirm
the wavelike nature of electrons.
Werner Heisenberg states the quantum uncertainty principle.
Bohr formulates complementarity principle.
|1932||Chadwick discovers the neutron.
John Douglas Cockcroft and Ernest Thomas Walton achieve the transmutation of elements by protons.
Anderson discovers the positron.
|1934||Lawrence and Livingston construct the cyclotron.
Leo Szilard realizes that nuclear chain reactions may be possible.
|1939||Otto Hahn and Fritz Strassman obtain the first atomic fission with uranium.|
|1942||Enrico Fermi makes the first controlled nuclear chain reaction.
The Manhattan Project is launched.
|1945||First thermonuclear fission bomb exploded at Alamogordo in the New Mexico desert.|
|1946||The carbon-14 dating technique is developed by Willard Frank Libby.|
|1952||The first hydrogen bomb, Mike, is detonated.|
|1953||Watson and Crick construct a three-dimensional model of the DNA molecule.|
|1972||Workers at Stanford University construct the first recombinant DNA molecules using restriction enzymes and DNA ligase.|
|1973||Public concern swell over the possibility of the production of potentially dangerous microorganisms by recombinant DNA technology.|
|1975||An international conference is held in Asilomar, California, urging strict guidelines regulating recombinant DNA research.|
|1977||Genentech, the first genetic engineering company, is founded to use recombinant DNA methods to produce medically important drugs.|
|1980||The Nobel Prize in Chemistry is awarded for the creation of the first recombinant DNA molecules and the development of powerful DNA sequencing methods.|