Geology Reference
In-Depth Information
research. In their fourth and final year students were expected
to contribute original research work for assessment with their
final exams, so here was an opportune moment to start. As part
of his physics lectures Professor Strutt had run a course on
radioactivity and had been impressed with this young man's
advanced understanding of the subject, so Strutt invited Holmes
to help him with his research on radioactivity that he had started
at the Cavendish.
Once Rutherford and Soddy had established that the helium
found in rocks was due to the decay of radioactive elements, and
that the heat generated by radioactivity was enough to keep the
Earth hot for as long as geologists needed, it was but a short
step to realising that if the rate of helium production could be
established, and the amount of helium that had accumulated in
a rock was measured, then a relatively simple calculation would
show how long it had taken for the helium to accumulate, and
the real age of the rock could be established. The di~cult bit
was in establishing the rate of helium production.
Do you by any chance remember the days before digital
watches? When I was eleven years old my father gave me my first
watch. In those days a watch was a symbol that you were grow-
ing up, it meant you were old enough to look after something
expensive that was expected to last a long time, and I was
immensely thrilled that my parents considered I had reached
that age. But when I took the watch out of the box, I was a lit-
tle disappointed. It looked very odd: in place of the usual num-
bers on the dial there were little green dots, and the hands were
painted green as well. My father must have seen the look on my
face because he told me to look at it under the bed clothes, and
there I saw a wonderful sight. The dots and hands were glow-
ing so that I could tell the time in the dark. I grew to love that
watch as my most treasured possession and would place it each
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