Timeline of Particle Discoveries
1897_____ Electron Discovered. J.J. Thompson in studying the discharge of electricity through gases found negatively charged particles having small mass when compared to the atomic mass.
1905_____ Photon Born. Einstein using Planck�s idea of quantum extends the idea further and assumes light exists as quanta (called photons).
1919_____ Proton Exposed. Ernest Rutherford using natural radioactive source breaks apart a nitrogen nuclei and showed that hydrogen nuclei were produced giving the name of these nuclei � protons.
1930_____ Pauli postulates the existence of a neutral invisible particle he names the neutrino.
1932_____ Neutron Revealed. Chadwick�s experiments could be explained by the existence of a neutral particle that had protonic mass.
1932_____ Positron Verified. Dirac�s prediction was experimentally verified by Anderson who was studying cosmic rays.
1935_____ Yukawa�s prediction of Mesons.
1937_____ Muon Discovered. It was thought that these particles were the ones predicted by Yukawa but closer examination revealed a weaker interacting particle.
1947_____ Pion Discovered.
1956_____ Direct Observation of Neutrinos.
1963_____ Experimental Discovery of Neutrinos of Different Flavor.
1964_____ Quark-Lepton Symmetry and Charm Quark Proposal. Only three quarks were known: the u, d, and s quarks.
1973-4___ Standard Model Formulated. The ideas of Weinberg, Salam, and by Glashow, on electroweak unification gradually leads to this model.
1974_____ Charm Quark Discovered. The charm quark together with the strange quark complete the second generation of quarks.
1975_____ Tau Lepton Found.
1977_____ Discovery of the Bottom Quark. Existence of a top quark needed to be found based on the standard model.
1979_____ Evidence for Gluons found.
1983_____ Discovery of the W and Z bosons. With these discoveries the standard electroweak model was placed on a strong footing.
1995_____ Top Quark Revealed. Discovered by the CDF and DO groups at the Fermilab.
2000_____ Tau Neutrino Exposed. A collaboration of the University of Minnesota and the Fermilab.
???? _____ Higgs particle found and more generations of subatomic particles!
