Father Francesco Maria Grimaldi, SJ
Discoverer of the Diffraction of Light



Father Francesco Maria Grimaldi, SJ on Monaco Scott 2546
MONACO, 2009, Europa issue honoring astronomers, Scott 2546

Francesco Grimaldi was an Italian physicist who was born and died in Bologna. He entered the Jesuits in 1632; and, after the usual studies, spent twenty-five years as professor of mathematics and physics at the Jesuit college in Bologna. His most important scientific work was done in optics; he discovered the diffraction of light, the principle of interference, and the dispersion of the sun's rays in passing through a prism. His treatise Physical Knowledge of Light: the Colors of the Rainbow published in 1665 secures for him a place in the history of optics. Isaac Newton praised him in his 1704 work, Optiks. He assisted another Jesuit, Fr. Giovanni Battista Riccioli in his experiments in the 1640s on falling bodies, and in his surveys, in 1645, to determine the length of an arc of the meridian. He was a close observer of the moon's surface and constructed a map which was incorporated in Riccioli's Almagestum Novum. This Riccioli/Grimaldi map provided the basis for the system of lunar nomenclature still in use. Riccioli named two adjacent craters Grimaldus and Ricciolus, the first shown in red on this stamp, the second to the west of Grimaldus. Monaco probably chose to honor Grimaldi for this special Europa issue because of some connection with the Grimaldi's who are the ruling family of Monaco. More