Chronology of Quantum Mechanics, Molecular, Atomic, Nuclear, and Particle Physics

 -440 Democritus speculates about fundamental indivisible particles; calls them "atoms". 1766 Henry Cavendish discovers and studies hydrogen. 1778 Carl Scheele and Antoine Lavoisier discover that air is composed mostly of nitrogen and oxygen. 1781 Joseph Priestly creates water by igniting hydrogen and oxygen. 1800 William Nicholson and Anthony Carlisle use electrolysis to separate water into hydrogen and oxygen. 1803 John Dalton introduces atomic ideas into chemistry and states that matter is composed of atoms of different weights. 1811 Amedeo Avogadro claims that equal volumes of gases should contain equal numbers of molecules. 1832 Michael Faraday states his laws of electrolysis. 1871 Dmitri Mendeleyev systematically examines the periodic table and predicts the existence of gallium, scandium, and germanium. 1873 Johannes van der Waals introduces the idea of weak attractive forces between molecules. 1885 Johann Balmer finds a mathematical expression for observed hydrogen line wavelengths. 1887 Heinrich Hertz discovers the photoelectric effect. 1894 Lord Rayleigh and William Ramsay discover argon by spectroscopically analyzing the gas left over after nitrogen and oxygen are removed from air. 1895 William Ramsay discovers terrestrial helium by spectroscopically analyzing gas produced by decaying uranium. 1896 Antoine Becquerel discovers the radioactivity of uranium. 1896 Pieter Zeeman studies the splitting of sodium D lines when sodium is held in a flame between strong magnetic poles. 1897 Joseph Thomson discovers the electron. 1898 William Ramsay and Morris Travers discover neon, krypton, and xenon. 1898 Marie Curie and Pierre Curie isolate and study radium and polonium. 1899 Ernest Rutherford discovers that uranium radiation is composed of positively charged alpha particles and negatively charged beta particles. 1900 Paul Villard discovers gamma-rays while studying uranium decay. 1900 Johannes Rydberg refines the expression for observed hydrogen line wavelengths. 1900 Max Planck states his quantum hypothesis and blackbody radiation law. 1902 Philipp Lenard observes that maximum photoelectron energies are independent of illuminating intensity but depend on frequency. 1902 Theodor Svedberg suggests that fluctuations in molecular bombardment cause the Brownian motion. 1905 Albert Einstein explains the photoelectric effect. 1906 Charles Barkla discovers that each element has a characteristic X-ray and that the degree of penetration of these X-rays is related to the atomic weight of the element. 1909 Hans Geiger and Ernest Marsden discover large angle deflections of alpha particles by thin metal foils. 1909 Ernest Rutherford and Thomas Royds demonstrate that alpha particles are doubly ionized helium atoms. 1911 Ernest Rutherford explains the Geiger-Marsden experiment by invoking a nuclear atom model and derives the Rutherford cross section. 1912 Max von Laue suggests using lattice solids to diffract X-rays. 1912 Walter Friedrich and Paul Knipping diffract X-rays in zinc blende. 1913 William Bragg and Lawrence Bragg work out the Bragg condition for strong X-ray reflection. 1913 Henry Moseley shows that nuclear charge is the real basis for numbering the elements. 1913 Niels Bohr presents his quantum model of the atom. 1913 Robert Millikan measures the fundamental unit of electric charge. 1913 Johannes Stark demonstrates that strong electric fields will split the Balmer spectral line series of hydrogen. 1914 James Franck and Gustav Hertz observe atomic excitation. 1914 Ernest Rutherford suggests that the positively charged atomic nucleus contains protons. 1915 Arnold Sommerfeld develops a modified Bohr atomic model with elliptic orbits to explain relativistic fine structure. 1916 Gilbert Lewis and Irving Langmuir formulate an electron shell model of chemical bonding. 1917 Albert Einstein introduces the idea of stimulated radiation emission. 1921 Alfred Lande introduces the Lande g-factor. 1922 Arthur Compton studies X-ray photon scattering by electrons. 1922 Otto Stern and Walter Gerlach show "space quantization". 1923 Louis de Broglie suggests that electrons may have wavelike properties. 1924 Wolfgang Pauli states the quantum exclusion principle. 1924 John Lennard-Jones proposes a semiempirical interatomic force law. 1924 Satyendra Bose and Albert Einstein introduce Bose-Einstein statistics. 1925 George Uhlenbeck and Samuel Goudsmit postulate electron spin. 1925 Pierre Auger discovers the Auger autoionization process. 1925 Werner Heisenberg, Max Born, and Pascual Jordan formulate quantum matrix mechanics. 1926 Erwin Schrodinger states his nonrelativistic quantum wave equation and formulates quantum wave mechanics. 1926 Erwin Schrodinger proves that the wave and matrix formulations of quantum theory are mathematically equivalent. 1926 Oskar Klein and Walter Gordon state their relativistic quantum wave equation. 1926 Enrico Fermi discovers the spin-statistics connection. 1926 Paul Dirac introduces Fermi-Dirac statistics. 1927 Clinton Davission, Lester Germer, and George Thomson confirm the wavelike nature of electrons. 1927 Werner Heisenberg states the quantum uncertainty principle. 1927 Max Born interprets the probabilistic nature of wavefunctions. 1928 Chandrasekhara Raman studies optical photon scattering by electrons. 1928 Paul Dirac states his relativistic electron quantum wave equation. 1928 Charles G. Darwin and Walter Gordon solve the Dirac equation for a Coulomb potential. 1929 Oskar Klein discovers the Klein paradox. 1929 Oskar Klein and Y. Nishina derive the Klein-Nishina cross section for high energy photon scattering by electrons. 1929 N.F. Mott derives the Mott cross section for the Coulomb scattering of relativistic electrons. 1930 Paul Dirac introduces electron hole theory. 1930 Erwin Schrodinger predicts the zitterbewegung motion. 1930 Fritz London explains van der Waals forces as due to the interacting fluctuating dipole moments between molecules. 1931 John Lennard-Jones proposes the Lennard-Jones interatomic potential. 1931 Irene Joliot-Curie and Frederic Joliot-Curie observe but misinterpret neutron scattering in parafin. 1931 Wolfgang Pauli puts forth the neutrino hypothesis to explain the apparent violation of energy conservation in beta decay. 1931 Linus Pauling discovers resonance bonding and uses it to explain the high stability of symmetric planar molecules. 1931 Paul Dirac shows that charge conservation can be explained if magnetic monopoles exist. 1931 Harold Urey discovers deuterium using evaporation concentration techniques and spectroscopy. 1932 John Cockcroft and Thomas Walton split lithium and boron nuclei using proton bombardment. 1932 James Chadwick discovers the neutron. 1932 Werner Heisenberg presents the proton-neutron model of the nucleus and uses it to explain isotopes. 1932 Carl David Anderson discovers the positron. 1933 Max Delbruck suggests that quantum effects will cause photons to be scattered by an external electric field. 1934 Irene Joliot-Curie and Frederic Joliot-Curie bombard aluminum atoms with alpha particles to create artificially radioactive phosphorus-30. 1934 Leo Szilard realizes that nuclear chain reactions may be possible. 1934 Enrico Fermi formulates his theory of beta decay. 1934 Lev Landau tells Edward Teller that nonlinear molecules may have vibrational modes which remove the degeneracy of an orbitally degenerate state. 1934 Enrico Fermi suggests bombarding uranium atoms with neutrons to make a 93 proton element. 1934 Pavel Cerenkov reports that light is emitted by relativistic particles traveling in a nonscintillating liquid. 1935 Hideki Yukawa presents a theory of strong interactions and predicts mesons. 1935 Albert Einstein, Boris Podolsky, and Nathan Rosen put forth the EPR paradox. 1935 Niels Bohr presents his analysis of the EPR paradox. 1936 Eugene Wigner develops the theory of neutron absorption by atomic nuclei. 1936 Hans Jahn and Edward Teller present their systematic study of the symmetry types for which the Jahn-Teller effect is expected. 1937 H. Hellmann finds the Hellmann-Feynman theorem. 1937 Seth Neddermeyer, Carl Anderson, J.C. Street, and E.C. Stevenson discover muons using cloud chamber measurements of cosmic rays. 1939 Richard Feynman finds the Hellmann-Feynman theorem. 1939 Otto Hahn and Fritz Strassman bombard uranium salts with thermal neutrons and discover barium among the reaction products. 1939 Lise Meitner and Otto Frisch determine that nuclear fission is taking place in the Hahn-Strassman experiments. 1942 Enrico Fermi makes the first controlled nuclear chain reaction. 1942 Ernst Stuckelberg introduces the propagator to positron theory and interprets positrons as negative energy electrons moving backwards through spacetime. 1943 Sin-Itiro Tomonaga publishes his paper on the basic physical principles of quantum electrodynamics. 1947 Willis Lamb and Robert Retheford measure the Lamb-Retheford shift. 1947 Cecil Powell, C.M.G. Lattes, and G.P.S. Occhialini discover the pi-meson by studying cosmic ray tracks. 1947 Richard Feynman presents his propagator approach to quantum electrodynamics. 1948 Hendrik Casimir predicts a rudimentary attractive Casimir force on a parallel plate capacitor. 1951 Martin Deutsch discovers positronium. 1953 R. Wilson observes Delbruck scattering of 1.33 MeV gamma-rays by the electric fields of lead nuclei. 1954 Chen Yang and Robert Mills investigate a theory of hadronic isospin by demanding local gauge invariance under isotopic spin space rotations; first non-Abelian gauge theory. 1955 Owen Chamberlain, Emilio Segre, Clyde Wiegand, and Thomas Ypsilantis discover the antiproton. 1956 Frederick Reines and Clyde Cowan detect antineutrinos. 1956 Chen Yang and Tsung Lee propose parity violation by the weak force. 1956 Chien Shiung Wu discovers parity violation by the weak force in decaying cobalt. 1957 Gerhart Luders proves the CPT theorem. 1957 Richard Feynman, Murray Gell-Mann, Robert Marshak, and Ennackel Sudarshan propose a V-A Lagrangian for weak interactions. 1958 Marcus Sparnaay experimentally confirms the Casimir effect. 1959 Yakir Aharonov and David Bohm predict the Aharonov-Bohm effect. 1960 R.G. Chambers experimentally confirms the Aharonov-Bohm effect. 1961 Murray Gell-Mann and Yuval Neeman discover the Eightfold Way patterns; SU(3) group. 1961 Jeffery Goldstone considers the breaking of global phase symmetry. 1962 Leon Lederman shows that the electron neutrino is distinct from the muon neutrino. 1963 Murray Gell-Mann and George Zweig propose the quark/aces model. 1964 Peter Higgs considers the breaking of local phase symmetry. 1964 J.S. Bell shows that all local hidden variable theories must satisfy Bell's inequality. 1964 Val Fitch and James Cronin observe CP violation by the weak force in the decay of K mesons. 1967 Steven Weinberg puts forth his electroweak model of leptons. 1969 J.C. Clauser, M. Horne, A. Shimony, and R. Holt propose a polarization correlation test of Bell's inequality. 1970 Sheldon Glashow, John Iliopoulos, and Luciano Maiani propose the charm quark. 1971 Gerard 't Hooft shows that the Glashow-Salam-Weinberg electroweak model can be renormalized. 1972 S. Freedman and J.C. Clauser perform the first polarization correlation test of Bell's inequality. 1973 David Politzer proposes the asymptotic freedom of quarks. 1974 Burton Richter and Samuel Ting discover the psi meson implying the existence of the charm quark. 1975 Martin Perl discovers the tauon. 1977 S.W. Herb finds the upsilon resonance implying the existence of the beauty quark. 1982 A. Aspect, J. Dalibard, and G. Roger perform a polarization correlation test of Bell's inequality that rules out conspiratorial polarizer communication. 1983 Carlo Rubbia, Simon van der Meer, and the CERN UA-1 collaboration find the W$^\pm$ and Z$^0$ intermediate vector bosons. 1989 The Z$^0$ intermediate vector boson resonance width indicates three quark-lepton generations.