Chamberlin, Thomas Chrowder (1843-1928)

US geophysicist who asserted that the Earth was far older than then believed. He developed the planetesimal hypothesis for the origin of the Earth and other planetary bodies - that they had been formed gradually by accretion of particles.

Chamberlin was born in Illinois and brought up in Wisconsin. Partly self-taught in science, he joined the Wisconsin Geological Survey 1873, and rose to become its chief geologist, publishing Geology of Wisconsin 1877-83. He went on to work for the US Geological Survey before becoming professor at Chicago 1892-1918.

Irish physicist Lord Kelvin had postulated that the Earth was less than 100 million years old, basing his views on the assumption, derived from the nebular hypothesis, that the Earth had steadily cooled from a molten mass. Chamberlin countered this with the planetesimal hypothesis, and believed geological evidence in any case suggested the Earth to be older than Kelvin had estimated; a theory that came much closer to the current estimate of the Earth's age at 4.6 billion years.