Picard, Jean, 1620–82, French astronomer, noted for having made the first accurate measurement of a degree of the earth's meridian. The figures he established were of great value to Newton in his calculation of the force of gravitation. Picard, who had previously been the prior of Rillé, in Anjou, went to Paris to occupy the chair of astronomy in the Collège de France in 1655. He determined (1671) the latitude and longitude of Tycho Brahe's observatory at Ven (now Landskrona, Sweden) in order to be able to use Brahe's observations of the positions of heavenly bodies. To him is due in great part the establishment of the Paris Observatory and of the Connaissance des temps, the first five volumes (1679–83) of which he wrote.