WILLIAMSTOWN, Mass. — Ideas about what the world is made of — its constituent elements — were running riot when Edvard Munch (1863-1944) came into his own as an artist. Geology — and specifically stratigraphy, or the study of rock layers — had rolled back the age of the Earth by hundreds of millions of years. An 1886 experiment by Heinrich Hertz had meanwhile demonstrated the existence of electromagnetic waves, proving James Clerk Maxwell’s idea that electricity, magnetism and light were different manifestations of the same phenomenon.