ABSTRACT
Neil Bohr's scientific life started in 1905. It was the year in which the first paper on relativity was published by Einstein, the existence of the photon was recognized by Einstein; five years earlier Planck started quantum theory. The author likes to divide Bohr's life into four periods. The first period extends roughly from 1910 to 1922. He met Ernest Rutherford, at the beginning of that period in Manchester. Then came the second period roughly from 1922 to 1930. The author calls it the 'heroic' period. It was the time of the birth of quantum mechanics, the logical basis of his earlier intuitive ideas. The third period is from 1930 to 1940. At that time his main interests centered upon nuclear physics and quantum field theory. The fourth period is from 1940 to his death in 1962. That was the time of the Second World War, of the occupation of Denmark, his flight to Sweden.
