Italian physicist Francesco Maria Grimaldi (1618-1663) is best known for his description of the diffraction (bending) of light and his observation of the surface of the moon. Grimaldi became interested in astronomy as a student, when he worked as a research assistant for professor Giovanni Riccioli. Grimaldi also built a telescope with a very accurate micrometer, which is an instrument that precisely measures distances. Using this telescope, he made hundreds of drawings that he pieced together to form a map of the features of the moon's surface. Grimaldi's name lives on via the large crater 23O on the moon named after him.
Grimaldi's most significant work, however, came later in the field of optics (the study of light). He was the first scientist to record the effects of light diffraction. Grimaldi's discovery was important because it came at a time when light was believed to be made up of particles. But Grimaldi's findings indicated that light seemed to consist of waves. We now know that light can behave both as particles and waves. Grimaldi also noticed a band of color at the edge of a diffracted light beam. He carefully recorded these colored streaks, but was unable to determine what caused them. It was not until 150 years later that German optician Joseph von Fraunhofer discovered that these colored bands were made up of various wavelengths of light.
