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lab assistants Marie and Pierre Curie, next sought to understand
what had happened. They realized that certain elements are fun-
damentally unstable, and this instability leads their isotopes (dif-
ferent species of an element, the difference being the number of
neutrons) to undergo spontaneous decay, to break apart, and to
ultimately produce stable atoms, along with energy. This action
is known as radioactive decay, and a by-product is the escape of
the energy. It was this energy that caused the exposure of the film.
The discovery of radioactivity galvanized the world of sci-
ence, and ambitious scientists everywhere began working in the
field. The next big breakthrough occurred in 1902, when Ernst
Rutherford and his colleague Frederick Soddy showed that
radioactive decay of a given element occurs at a constant rate,
EPI LOGUE 203
one that can be measured. It was not long before they realized
that the steady rate of radioactive decay could be used as a geo-
logic clock to determine the age of the earth. In 1905, Ruther-
ford delivered the Silliman Lectures at Yale, and used the forum
to challenge the science community to try to date the age of the
earth using this new natural clock.
A chemist soon took up the Rutherford-Soddy challenge.
In 1907, Bertram Boltwood used the known rate of decay of
radium, combined with his discovery that uranium decays to
lead, to come up with a range of 400 million to 2,200 million
years for the age of the earth.
The next push to date the earth moved back to the United
Kingdom in the person of Arthur Holmes (1890 1965). Holmes
was a gifted student who had won a science scholarship to study
physics at Imperial College in London. When his talents were
recognized by the physicist R. J. Strutt, Holmes was urged to stay
on as a graduate student to work on the age of the earth prob-
lem. Holmes followed Boltwood s insight into the relationship
between uranium and lead, and came up with more refined num-
bers. In 1913, and again in 1927, he published a popular book
on the age of the earth, in which he presented his calculation that
the earth was 1.6 billion years old.
Through the 1930s and 1940s the work of Holmes, Alfred
Nier, E. Gerling, and F. Houtermans became more rigorous and
precise. These men, and many others, were now working pri-
marily with common lead, and by the beginning of World
War II, isotope geologists had now calculated the age of the
earth to be at least 3.3 billion years.
204 THE MAN WHO FOUND TI ME
The final breakthrough came in the 1950s, when Claire Pat-
terson, of Caltech, realized that the only way to get a completely
accurate measurement of common lead decay was to leave the
planet, since the complicated mix of other elements in the earth
distorted any measurement attempt. He and his colleagues
decided to focus on objects that were the same age as all the
planets in the solar system, including the earth, but allowed for
more accurate lead decay calculations meteorites. As Claire
Patterson later related:
Lead in iron meteorites was the kind of lead that was in the
solar system when it was first formed, and . . . it was pre-
served in iron meteorites without change from uranium
decay, because there is no uranium in iron meteorites. . . . If
we only knew what the isotopic composition of primordial
lead was in the earth when formed, we could take that num-
ber and stick it into this marvelous equation that the atomic
physicists had worked out. And you could turn the crank and
blip out would come the age of the earth.
By 1956, Patterson had calculated the age of the earth to be
4.6 billion years, which remains the accepted age of our planet.
James Hutton was right the earth is unfathomably old.
Why is it that James Hutton, the man who proved the earth s
antiquity and made it possible for Claire Patterson to complete
his work, is essentially unknown to all but geologists? One reason
for his relative invisibility is that geology has never been a partic-
EPI LOGUE 205
ularly flashy discipline. And it seems to have done an especially
poor job of publicizing its founding fathers, whereas other scien-
tific fields have somehow pushed their pioneers into the popular
consciousness: Lavoisier in chemistry, Galileo and Newton in
physics, Darwin and Gregor Mendel in biology. However, that
cannot be the whole story because most people have at least
heard of Charles Lyell, the discipline s other trailblazer.
Another reason is that the world s attention was certainly
focused elsewhere when Hutton was first presenting and then
defending his theory. The American War of Independence
ended in 1783, and the French Revolution began in 1789 two
galvanizing events that changed world history forever, and cer-
tainly preoccupied the people who lived through the last
decades of the eighteenth century, as well as future historians.
Still, these two conflagrations did not prevent Adam Smith from
gaining the recognition he deserved.
One is left with the fact that James Hutton was not a gifted
communicator. Indeed, just about the only negative passage in
Playfair s biography concerns Hutton s writing: The reasoning
is sometimes embarrassed by the care taken to render it strictly
logical; and the transitions, from the author s peculiar notions of
arrangement, are often unexpected and abrupt. These defects
run more or less through all Dr. Hutton s writings, and produce
a degree of obscurity astonishing to those who knew him, and
heard him everyday converse with no less clearness and preci-
sion than animation and force.
The defective writing, coupled with the great pain Hutton
was suffering while working on his book, caused it to be put
206 THE MAN WHO FOUND TI ME
together in a hurried way. Not just long (approximately 1,200
pages over two volumes), The Theory of the Earth also con-
tained turgid passages from other works in other languages. A
book that unwieldy simply would not be read today, and it was
not widely read then. One historian has determined that the
first printing was just 500 copies (not an unusual first printing
for the time; the first printing for Origin of Species was just
1,250 copies), but it was never reprinted. The long article from
1788 was a solid piece of scientific writing, but it was available
only in a volume containing several other papers, and it was not
broadly distributed.
That Hutton s book was virtually ignored by readers in
1795, and thereafter, seemed to seal his fate as a member of the
legion of forgotten scientists. In fact, one might argue that the
key to being remembered by posterity is to write a popular
book. The works of Charles Lyell and Charles Darwin are
regarded as masterpieces, still wonderfully interesting and
insightful over 100 years after their publication. Adam Smith s
Wealth of Nations carries a similar status. David Hume s books,
though less widely read now, were best-sellers 200 years ago,
and are actively perused by philosophy students today. New-
ton s Principia, though technical, is still read by most serious
students of physics. John Playfair s own book, unlike Hutton s,
was well written and popular at the time, but perhaps it was pre-
vented from remaining visible over the decades because he was
explaining another s work.
Steno, Werner, Black, and Hall also did not write books
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