Seth Carlo Chandler

Seth Carlo Chandler, Jr. ( born September 16, 1846 in Boston, Massachusetts, † 31 December 1913 in Wellesley Hills, Massachusetts ) was an American astronomer.

In his last year in high school, he performed mathematical calculations for Benjamin Peirce of Harvard College Observatory.

After completing his studies was Chandler 's assistant Benjamin Apthorp Gould. Gould was director of the Longitude Department of the U.S. Coast Survey program in which it came to geodetic monitoring. When Gould went to Argentina, also Chandler left the observatory and was an insurance specialist. However, he worked as an amateur astronomer at Harvard College Observatory further.

Chandler's greatest scientific achievement is the discovery of the eponymous periodic circular motion of the Earth's rotation axis with respect to an earth-fixed coordinate system. The amplitude of this movement (so-called " Chandler wobble " ) is about 0.17 arcseconds, which corresponds to the surface 5 m. The mean oscillation period is 435 days. This also as "free polar motion " of the earth is called vibration due to the fact that the polar main inertia axis ( body axis ) does not coincide with the axis of rotation of the earth. Thus, a swaying motion of the flattened Erdkreisels caused. Why the rotation axis has not shifted in the course of the earth in the principal axis of inertia of the earth, is currently the subject of research. Recent studies suggest that mass displacements are responsible for maintaining the oscillation in the atmosphere and oceans.

Chandler also worked in other areas of astronomy such as the variable stars. He was an independent co-discoverer of Nova T Coronae Borealis, improved the determination of the constant of aberration and calculated orbital elements of asteroids and comets.

Chandler was awarded the Gold Medal of the Royal Astronomical Society in 1896 and the James Craig Watson Medal in 1894. A lunar crater has been named after him.