Originally Posted by JohnD

This debate parallels that between Darwin and Lord Kelvin in the 19th century. Kelvin calculated from the properties of Earth rocks and estimates of the initial temperature that the Earth could be no more than 100 million years old, which was far too little time for Darwin's theory to take effect. Extraordinarily, when his theory was attacked, pricipally for ignoring convection ("Are you mad,Sir? In the solid Earth?!") in favour of conduction, he revised his estimate - downwards! To 20 million years!

See: http://www.usd.edu/esci/age/content/...n_cooling.html

John