Readers of this blog know that I have sometimes pointed at Emperor Lord Kelvin’s fragile suit of clothing. Although his early life was crammed with brilliant science, he was a fumbling troglodyte by age 50. He became resistant to scientific novelty, dismissing X-rays as a hoax and claiming aeroplanes would never be practical. He was not an Earth scientist, but he used his physics of thermodynamics to insist that the Earth and Sun were no more than 20 million years old. Kelvin’s idea was two-fold: The Sun could not produce heat for longer than a few million years because it would run out of energy; meanwhile, the Earth’s internal heat should have dissipated if the Earth were much older.
For years, Lord Kelvin’s powerful name and adamant errors prevented geologists from using Charles Darwin’s earth-age estimate (300 million years) for solving geological puzzles that required vast amounts of time for their slow processes (especially erosion and geomorphology) to take place.
Particularly, Darwin measured the rate of erosion of southeast England’s chalky Weald mountains. He decided it took at least 300 million years to erode those broad deep valleys. But Lord Kelvin put scientists in an awkward position – does one print what seems to be true, or does one subvert the truth to massage Kelvin’s ego?
Ernest Rutherford disagreed with Lord Kelvin. Born on this date in 1871 (Happy Birthday, Professor Rutherford!) on a farm in New Zealand, Rutherford’s Nobel Prize-winning work (He discovered radioactivity half-life, distinguished alpha from beta particles, and showed elements change into new elements during decay.) was all done at Canada’s McGill University between 1898 and 1907. During this time, Rutherford was invited to address the Royal Institution, in London, in 1904. There, unfortunately, he would need to confront Lord Kelvin with new evidence (radioactive heat) that allowed for of a much, much older Earth and Sun.
In London, Rutherford lectured the assembly of distinguished scientists about atomic structure and radiation – and about the implications of radioactive heat and the age of the Earth. He was a rising star, age 33. He knew that his statements about the age of the Earth would offend the stately Lord Kelvin. Kelvin, age 80, held steadfastly to calculations that had become untenable. Rutherford’s idea that radio-active heat continually warms the planet disproved Kelvin’s age estimates, which were based on heat dissipation. By 1904, he and other scientists had gone beyond Darwin’s calculations and estimated the Earth was at least a billion years old. Rutherford anticipated Lord Kelvin would be in attendance at the presentation. Here is how Rutherford remembered it:
“I came into the room, which was half dark, and presently spotted Lord Kelvin in the audience and realized that I was in for trouble at the last part of the speech dealing with the age of the Earth, where my views conflicted with his. To my relief he fell fast asleep but as I came to the important point, I saw the old bird sit up, open an eye and cock a baleful glance at me! Then sudden inspiration came, and I said, Lord Kelvin had limited the age of the Earth, provided no new source of heat was discovered. That prophetic utterance refers to what we are now considering tonight, radium! Behold! The old boy beamed at me.”
And so it was. One of the last stalwart opponents to the idea of a very ancient age for the Earth was quite literally awoken to a new reality in physics. The next year Einstein would produce his series of papers. I have never found Kelvin’s reaction to the theories of relativity, but at least we know that he probably understood what Ernest Rutherford was saying. And Rutherford had graciously found a way for Lord Kelvin’s ego to remain intact. How old is the Earth? Carl Sagan went beyond Kelvin’s 20 million, Darwin’s 300 million, and Rutherford’s one billion. OK, I know Sagan was an astrophysicist, not a geophysicist. But I like the way he used to say Billions and Billions. . .