Sixth Solvay Physics Conference, Brussels, 1930.

BELGIUM - JUNE 10: Delegates attending the 6th of the Solvay Physics Conferences which were initiated by Belgian chemist and industrialist Ernest Solvay (1838-1922). The delegates shown here included such luminaries as Marie Curie (1867-1934), Paul Dirac (1902-1984), Albert Einstein (1879-1955), Paul Langevin (1872-1946) and Niels Bohr (1885-1962). (Photo by SSPL/Getty Images)