1885 – Niels Bohr is born on October 7, in Copenhagen.
1887 – Brother, Harald, is born on April 22.
1903 – Bohr leaves Gammelholm School, enters University of Copenhagen.
1905 – Albert Einstein publishes special theory of relativity.
1906-1907 Research on surface tension of liquids for Royal Danish Academy competition. Bohr is awarded Gold Medal.
1909 – Receives master’s degree. Publishes medal-winning work on surface tension.
1911 – Receives doctorate. Thesis on electron theory of metals.
1911-1912 Bohr in Cambridge. Meets J. J. Thomson. Ernest Rutherford postulates the nuclear atom.
1912 – Bohr joins Rutherford at Manchester; meets George de Hevesy. Appointed assistant at University of Copenhagen. Marries Margrethe Norlund.
1913 – W. H. Bragg, W. L. Bragg, Henry Moseley, and Max von Laue develop x-ray spectroscopy. Bohr’s trilogy, “On the Constitution of Atoms and Molecules,” is published. Bohr appointed lecturer at University of Copenhagen.
1914-1916 Holds Schuster Readership at Manchester University.
1915 – Arnold Sommerfeld generalizes the orbital quantum conditions. Albert Einstein develops general theory of relativity.
1916 – Bohr appointed professor of theoretical physics at University of Copenhagen. Hendrik Kramers comes to work with him.
1917 – Bohr elected to Royal Danish Academy. Begins planning the Institute for Theoretical Physics.
1918-1922 Publishes three papers under the general title “On the Quantum Theory of Spectra,” embodying the development of the correspondence principle. Oskar Klein comes to Copenhagen.
1919 – Rutherford discovers nuclear disintegration caused by alpha particles. George de Hevesy comes to Copenhagen.
1920 – Bohr visits Berlin. Bonzenfreie Kolloquium. Meets Max Planck, Einstein, and James Franck. Rutherford visits Copenhagen.
1921 – Bohr awarded the Hughes Medal of the Royal Society. University Institute for Theoretical Physics (“Bohr Institute”) opens.
1922 – Bohr visits Cambridge University (Rutherford now Cavendish Professor). Visits University of Göttingen. Bohr Festspiele. Meets Wolfgang Pauli and Werner Heisenberg. Pauli joins institute. Bohr publishes theory of the periodic system. Identification and discovery of hafnium (element 72). Bohr receives Nobel Prize for physics.
1923 – First visit to the United States. Meets Albert Michelson and Arthur Compton. Offered Royal Society chair at Cambridge University. John C. Slater arrives in Copenhagen.
1924 – Visits to institute by Friedrich Paschen, Max Born, and Heisenberg, Rockefeller International Education Board donates $40,000 for expansion of facilities.
1925 – Foundation of matrix mechanics (Heisenberg). Discovery of the exclusion principle (Pauli) and electron spin (Uhlenbeck and Goudsmit).
1926 – Heisenberg revisits institute; Kramers and Hevesy leave. Visits by Erwin Schrödinger, P. A. M. Dirac, and Samuel Goudsmit. Bohr elected a Foreign Member of the Royal Society.
1927 – Uncertainty principle (Heisenberg) and complementarity argument (Bohr) are formulated. Dirac develops relativistic electron theory. Como conference. Fifth Solvay conference (the Bohr-Einstein debates).
1928 – George Gamow arrives at institute; Nevill Mott visits. Birth of liquid-drop model of nucleus (Gamow).
1929 – First of annual institute conferences. Hendrik Casimir visits Copenhagen. Ernest Lawrence invents the cyclotron.
1930 – Visits to institute by Lev Landau and Rudolf Peierls. Bohr awarded Planck Medal of Deutsche Physikalische Gesellschaft. J. D. Cockcroft and E. T. S. Walton achieve first artificial nuclear transmutations.
1932 – Bohr family moves to Carlsberg House of Honor. James Chadwick discovers the neutron.
1933 – Bohr works on quantum electrodynamics with Léon Rosenfeld. Develops measurement theory for electromagnetic fields. Begins aid for refugee scientists. Otto Frisch visits institute. Bohr, with his wife, visits the United States, stopping at University of Chicago and California Institute of Technology. Meets Robert Millikan and J. Robert Oppenheimer. Seventh Solvay conference (on nuclear physics).
1934 – Frisch joins staff of institute. Next door, the University Institute of Mathematics opens, with Harald Bohr as director. The Bohr’s eldest son, Christian, is drowned in a sailing accident. Irène and Frédéric Joliot-Curie discover artificial radioactivity. Enrico Fermi publishes theory of beta decay.
1936 – Bohr develops compound-nucleus theory, with Fritz Kalckar.
1937 – Bohr, with wife and son Hans, makes six-month trip around the world. Visits United States, Japan, China, and USSR. Death of Rutherford; Bohr attends funeral at Westminster Abbey.
1938 – Installation of cyclotron at Bohr Institute.
1939 – Discovery of nuclear fission by Otto Hahn and Fritz Strassmann, and Lise Meitner and Otto Frisch. Reported by Bohr during visit to United States. Bohr and John Wheeler write classic paper on theory of fission. Bohr elected president of Royal Danish Academy of Sciences. World War II begins.
1940 – German occupation of Denmark.
1943 – Bohr and family escape to Sweden. Bohr, with son Aage, proceeds to Britain and the United States (Washington and Los Alamos).
1944 – Meetings with Roosevelt and Churchill.
1945 – First atomic bomb exploded. Hiroshima and Nagasaki destroyed. World War II ends. Bohr returns to Denmark in August.
1946 – Abraham Pais becomes first postwar foreign member of Bohr Institute.
1949 – USSR detonates a fission bomb. Bohr revisits United States.
1950 – Open letter to the United Nations.
1952 – United States explodes its first hydrogen bomb. Foundation of CERN.
1955 – First “Atoms for Peace” conference (Geneva). Death of Einstein.
1957 – Bohr receives the first Atoms for Peace Award. NORDITA established in Copenhagen.
1958 – Bohr appointed chairman of Danish Atomic Energy Commission. Delivers Rutherford Memorial Lecture.