Early Theories and Estimates of the Earth's Age, Lecture notes of Earth Sciences

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Early attempts to date the age

of the Earth

Archbishop Ussher - 1654 Added up all the generations after Adam, and came up with an age of the Earth as 5,658 years old, having formed in 4004 B.C on October 12rd at 9 am. Herodotus - Greek historian, dated the age of the Earth using the rate of growth he observed in the Nile Delta; Earth was several thousand years old.

Lord Kelvin 1846- Quantified Buffon’s early ideas of an originally molten Earth which cooled to its present state as a result of the dissipation of heat over time. a. Rocks melt at ~3,900°C b. Assumed a geothermal gradient of ~0.56ºC/50 feet depth c. Derived mathematical estimates for thermal conductivity So that….at a depth of 50-100 miles the interior would still be molten (where magma was derived). He then determined that the geothermal gradient would have changed over time, so that at one point the surface itself would have been molten…at one point it was ~1º/foot!!) Result: age of Earth 20-400 million years old; later revised to 24-30 Ma Problems with his analysis???

An “old Earth” was incorporated into conceptions about how the Earth “worked” by scientists of the late 1800’s, including Darwin. This was, however NOT what the religious community and prevailing public opinion believed. Biologist T.H. Huxley Bishop of Oxford Samuel Wilberforce Darwin in 1859