Page 46 - The Restless Earth Fossils

so Many Fossils, so little time 45

century that they might be able to determine the age of the Earth
if they could figure out how long it would take for a planet-sized
blob of matter to cool down from a completely molten state.
The right man for this task appeared to be a Scottish math
teacher’s son named William Thompson (1824–1907), who later
became Baron Kelvin of Largs, or Lord Kelvin for short. Lord
Kelvin became a university freshman in 1834 when he was 10 and
had written his first mathematical paper by the age of 17. By the
time his career was over, he had written 500 scientific papers, had
invented electrical meters and navigation aids, and had helped
create the transatlantic cable between the United States and Great
Britain. In other words, the man had credentials.
Lord Kelvin did some math. He made a few general assump-
tions about the melting temperature of rock and whether some
heat energy might come from other chemical reactions as the
Earth cooled. He knew his figures were somewhat rough, but
overall he decided the Earth could not be much older than 100
million years. He also figured the Earth would have been cool
enough for living things to evolve for perhaps 20 to 25 million
years. That is a long time, but was it long enough for the pro-
cesses of evolution described by Darwin and supported by Lyell
and other scientists of the day? Could the great Lord Kelvin be
wrong? Could something else be keeping the Earth warm over
much longer stretches of time?
In 1898, Marie (1867–1934) and Pierre Curie (1859–1906)
discovered radium and polonium in pitchblende, an ore of ura-
nium. These new elements gave off unusual amounts of energy in
the form of X-rays and subatomic particles, which Marie called
radioactivity. Later, in 1903, Pierre Curie and Albert Laborde
found that radium gave off significant amounts of heat.
Ernest Rutherford (1871–1937) did further studies on radium
and confirmed its heat-generating properties. In a 1905 article in
Harper’s Magazine he wrote, “In the course of a year, one pound
of radium would emit as much heat as that obtained from the
combustion of one hundred pounds of the best coal, but at the

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