Week 4 Archaeology
Weekly Topics and subtopics
History of the Old Earth
The age of the Earth is crucial to understanding evolution and the fossil record, and the first expressed contemplation of an old Earth was associated with discussions of stratigraphy and biological evolution (Al Biruni, see Week 2).
Kelvin
Kelvin's initial 1864 estimate of the Earth's age was from 20 to 400 million years old. These wide limits were due to his uncertainty about the melting temperature of rock, to which he equated the Earth's interior temperature. Over the years he refined his arguments and reduced the upper bound by a factor of ten, and in 1897 Lord Kelvin ultimately settled on an estimate that the Earth was 20-40 million years old. The discovery in 1903 that radioactive decay releases heat led to Kelvin's estimate being challenged, and Ernest Rutherford famously made the argument in a lecture attended by Kelvin that this provided the unknown energy source Kelvin had suggested, but the estimate was not overturned until the development in 1907 of radiometric dating of rocks.
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