The Age of the Earth in the Twentieth Century

At the end of the nineteenth century, Lord Kelvin's upper limit of only 20 or 30 million years for the age of the Earth was challenged by the American geologist T. C. Chamberlin, who showed that Kelvin's model of an Earth gradually cooling from an initial molten state was not the only possible one. Kelvin's limit was soon afterwards repealed by the new science of radioactivity, which yielded ages of a few billion years. While some geologists resisted this expanded time-scale, Chamberlin was the only one who could provide a comprehensive cosmogonical theory that did not submit to the epistemological superiority of physics and astronomy. In the 1940s, as radiometric age determinations improved in accuracy, they came into conflict with the expanding-universe cosmology — a conflict which the cosmologists eventually avoided by expanding their distance and time scales. In 1953, Patterson announced the result 4.5 billion years, which is still accepted as the best estimate for the age of the Earth. But geologists, liberated from Kelvin's limit, define the epoch of the Earth's formation as being outside the scope of their science, and their textbooks rarely give credit to the person who established the number that once seemed so important to accounts of the Earth's history.