Читать книгу Professional Hairstyling - Joel Levy - Страница 17

With opposition to his views mounting, Kelvin was stung to respond. In 1897, he addressed the Victoria Institute with a talk entitled ‘The age of the Earth as an abode fitted for life’. Many assumed he would modify his views or relent. In fact, he was more dogmatic and intransigent than ever, revising his uppermost estimate of the age of the Earth to 24 million years, and talking grandly of ‘certain truths’.

The Badlands of Dakota. This was once the bed of an inland sea. Layers of rock have been revealed by aeons of gradual erosion – or perhaps by a Biblical deluge?

Unfortunately for Kelvin, new discoveries were at hand that would invalidate his fundamental assumption that the Earth had started with limited heat energy and lost heat ever since. Radioactivity had been discovered in 1896, and in 1903 the French chemist Pierre Curie realized the potential geological significance of heat generation by radioactive elements in rocks. The following year, the greatest of the new generation of physicists, Ernest Rutherford, lectured at the Royal Institution of Great Britain on the topic of radium and of radioactive elements as a source of heat energy. Noticing Lord Kelvin in the audience, he realized he was ‘in for trouble at the last part of my speech dealing with the age of the Earth, where my views conflicted with his. To my relief, Kelvin 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 a 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 upon me.’

In practice, Kelvin continued to deny that radioactivity had rewritten the rules of the debate. However, by the time he died in 1907, radioisotope dating was already being used to make direct measurements of the age of rocks, with samples dated at up to 2.2 billion years old. By 1931, the geologist Arthur Holmes was able to assure a US National Research Council meeting that ‘the age of the Earth exceeds 1,460 million years [and] is probably not less than 1,600 million years’. Modern dating techniques reliably prove that the Earth is around 4.55 billion years old (see box below).

‘As Lord Kelvin is the highest authority in science now living, I think we must yield to him and accept his views.’

MARK TWAIN, LETTERS FROM THE EARTH, 1909