Mutual Admiration

Abstract

Abstract The nature of the Bohr–Einstein debate was framed long before our protagonists became engaged in it. Both were reformers, ready to embrace controversy and even absurdity in their theories. But where Einstein held fast to classical principles he considered sacrosanct, Bohr would cheerfully embrace their violent reworking or replacement. Einstein’s 1921 Nobel prize was awarded in 1922. He had entertained the absurd notion that light consists of ‘quanta’, endowing particle-like properties governed by a characteristic wave frequency. Bohr’s 1922 Nobel prize involved entertaining the absurd notion of quantum ‘jumps’ between atomic orbits driven entirely by chance. He defended the inconsistencies with vague wordplay, declaring the quantities defining the orbits as ‘symbolic’, and introduced a fuzzy demand called the ‘correspondence principle’. At appropriate limits, the value of a quantity should be the same whether calculated using classical or quantum rules. Few quantum physicists could make it work.