Clausen, Thomas

BornSnogebæk, Denmark, 16 January 1801

DiedDorpat (Tartu, Estonia), 23 May 1885

Thomas Clausen was a specialist in the field of celestial mechanics and directed the Tartu Observatory (1865–1872). He was born into a poor family. At the age of 12, Clausen was sent to look after the cattle of a local priest. Father G. Holst discovered outstanding intellectual abilities in the boy and taught him Latin, Greek, mathematics, and astronomy. His later education was self-acquired. In 1823, Holst introduced Clausen to Heinrich Schumacher , director of the Altona Observatory and the founding editor of the Astronomische Nachrichten. Clausen handed to Schumacher a manuscript describing a method of measuring geographic longitudes by timing occultations of stars by the Moon. Clausen’s work was of high quality, and he became an assistant at Altona Observatory in 1824.

Four years later, Clausen succeeded Joseph von Fraunhofer at the Optical Institute at Munich. His position, however, carried few...