# 100 YEARS OF DISCOVERIES. Some key dates in the evolution of quantum theory and subatomic physics

Becquerel detects spontaneous emissions of energy from uranium (1891) Roentgen discovers X-rays (1895) J.J. Thomson detects the electron (1897) Planck theorizes ``the Quantum'' (1900) E=mc2 - Einstein's Special Theory of Relativity (1905) Bohr puts forward quantum rules for atomic structure (1913) Einstein's General Theory of Relativity (1915) Nuclear theory of the atom (proton discovered) by Rutherford (1919) Particle-wave duality shown (1923) Electron spin detected (1924) Pauli puts forth his exclusionary principle (1925) Heisenberg's matrix mechanics version of quantum theory (1926) Schr"odinger's wave mechanics version of quantum theory (1926) Hubble proposes an expanding universe (1929) Positron and neutron discovered (1932) Meson theory of the nuclear force (1934) Muon discovered (1937) Observation of strange particles (1947) Big bang theory (1955) Electron neutrinos detected (1956) Quarks hypothesized by Gell-Mann and Zweig (1963) Black holes discovered (1968) Color qualities assigned to quarks (1970s) Theory unifying weak and electromagnetic forces by Georgi and Glashow (1974) Charmed mesons (1976) W-bosons and Z-bosons (Rubbia, 1983) Superstring theory by Green and Schwartz (1985)