Pierre Bouguer

Pierre Bouguer (1698-1758) was a French surveyor, hydrographer and mathematician whose measurements of the Earth and of light belong to the groundwork of spaceflight-era science. Born at Le Croisic, he succeeded his father as Royal Professor of Hydrography while still a teenager and won three Grand Prix of the Academie Royale des Sciences, for work on ship masts, on observing the altitude of stars at sea and on magnetic declination at sea. In 1735 he joined the Academie expedition to Peru to measure the length of a degree of meridian at the equator, working with La Condamine and Louis Godin, and he was the first to try to weigh the Earth by the deflection of a plumb line near a mountain. He is called the father of photometry: in 1725 he compared the brightness of the Moon with a candle flame, and his 1729 essay set out Bouguer's law of the absorption of light in a uniform medium. A crater on the Moon and one on Mars bear his name.