theory, which encouraged scientists to find supporting data and not challenge it with difficult tests. The paper is considered a landmark on the scientific method, was an inspiration for the approach called strong inference, and was reprinted in 1965. In 1892 Chamberlin accepted the offer to organize a department of geology at the new University of Chicago, where he remained as a professor until 1918. From 1898 to 1914 he was president of the Chicago Academy of Sciences. In 1899 Chamberlin wrote, An Attempt to Frame a Working Hypothesis of the Cause of Glacial Periods on an Atmospheric Basis, and developed at length the idea that changes in climate could result from changes in the concentration of atmospheric carbon dioxide, and wrote about climate actions: In 1905, Chamberlin and Forest Ray Moulton developed a theory of the formation of the Solar System that challenged the Laplacian nebular hypothesis. Their theory, the Chamberlin-Moulton planetesimal hypothesis, received favorable support for almost a third of a century, but passed out of favor by the late 1930s. It ultimately was discarded in the 1940s by the realization it was incompatible with the angular momentum of Jupiter. A portion of the theory stating that smaller objects — planetesimals — gradually collided to build the planets by accretion is still well-regarded. From his theories and other geological evidence he concluded that Earth was much older than assumed by Lord Kelvin (ca 100 million years) at the time. His speculations about the source of energy for such a long-lived Sun were prescient, involving the ability of the Sun to somehow extract energy from the inner structures of the atom. Chamberlin was awarded the inaugural Penrose Gold Medal of the Society of Economic Geologists in 1924, and the inaugural Penrose Medal of the Geological Society of America in 1927. He was president of the Geological Society of America in 1894. Chamberlin remained active professionally up until his death in Chicago on November 15, 1928. His papers are housed at the University of Chicago archives and the Beloit College archives. The Beloit College archives also contain the papers of his son, Rollin T. Chamberlin (1881-1948), who was also a geologist, and later chaired the geology department at the University of Chicago. There are buildings named for him on the Beloit College and University of Wisconsin–Madison campuses as well as a house in Burton-Judson Courts at The University of Chicago.