Darwin had argued that the Earth was immensely old which gave his gradual process of evolution plenty of time to unfold.The great physicist Lord Kelvin had countered that the planet was actually relatively young perhaps 20 million years old.It turns out to be relatively well established, dating back more than 100 years to a book by Max O’Rell written in 1901, and the 1951 play The Moon is Blue.
The dates that radioactive clocks have put on evolutionary history are astonishing.
Nineteenth century geologists recognized that rocks formed slowly as mountains eroded and sediments settled on the ocean floor.
But they could not say just how long such processes had taken, and thus how old their fossils were.
He came up with that figure by estimating how long it had taken for the planet to cool down to its current temperature from its molten infancy.
But Kelvin didn't, and couldn't, know that radioactive atoms such as uranium were breaking down and keeping the planet warmer than it would be otherwise.