Francesco Maria Grimaldi

Born Apr. 2. 1618, in Bologna; died there Dec. 28, 1663. Italian physicist and astronomer; professor of mathematics at the Jesuit college in Bologna.

In his Physicomathematical Treatise on Light, Colors, and the Rainbow (published posthumously in 1665), Grimaldi gave a description of the diffraction of light, a phenomenon that he discovered. In his opinion, diffraction is caused by the appearance of waves in a luminous fluid striking the edges of an obstacle—that is, Grimaldi’s notions of light contain the rudiments of the wave theory of light. In collaboration with the Jesuit G. B. Riccioli, he compiled a map of the moon and introduced names for lunar formations that have been preserved to this day. He was an adversary of the heliocentric system and had a hand in drafting the Riccioli treatise directed against Copernicus.