Francesco Grimaldi (2.04.1618-28.12.1663) was an Italian scientist. He was born in Bologna, where in 1637—45 he studied philosophy, rhetoric and theology; in 1647 he received his doctorate and taught (philosophy at first and then mathematics) at the Jesuit College in Bologna. In 1651 he became a priest.
Grimaldi's main work, “A Physical Science of Light, Colours and the Rainbow”, which contains most of the results of his activity as an experimental physicist and a philosopher, appeared in 1665, after his death. He discovered the diffraction of light, studied it systematically and formulated certain rules. In his work he described in detail the phenomena of the propagation of light, of reflection, refraction, diffraction and vision, set out his (admittedly contradictory) views on the nature of light, and developed a theory of colours, regarding colour as a “modification of light”. He described the solar spectrum obtained with a prism. Together with G. Riccioli he determined (1662) the size of the Earth's surface.