Geology Reference
In-Depth Information
nised by its 'atomic' weight, which was the weight of one of its
atoms, because the weight of each element was different from
all the others.
So for almost a hundred years the idea that the atom was indi-
visible had become firmly entrenched in scientific thinking, and
now here was Marie Curie with evidence from the elements
uranium and thorium that the atom itself consisted of even
smaller parts, because it was the elements themselves that were
emitting these 'mysterious rays'. Her recognition of this radical
concept became the foundation stone for the whole future of
physics - the 'how' of dropping the atom bomb, the 'how' of
men on the moon. And although at this point we are a long way
from geological concerns, it was also to become the funda-
mental 'how' of dating the age of the Earth.
As Marie's work progressed she searched around for a vari-
ety of rocks that contained uranium, and discovered pitch-
blende, which was far more 'active' than it should have been,
considering the amount of uranium it contained. She speculat-
ed that a new element must be present. In fact, she discovered
not one but two new elements, both of which were significant-
ly more active than uranium. The first she called Polonium after
her native Poland; the second she called Radium from the Latin
word
radius
meaning 'ray'.
Radium was to become a crucial tool in early determinations
of the age of the Earth, but before that could happen Marie
would first have to prove its existence by extracting it from the
rock and producing it for everyone to see. It was a mammoth
task. Only the tiniest amounts of radium were present in pitch-
blende, seven tons contained about a gram, so at least two tons
would be needed to produce even the smallest visible quantity.
Pitchblende was also very expensive. An American newspaper of
the time reported that 'a ton of pitchblende carries about 15
1
/
2
grains of radium . . . this quantity is at present estimated to be
worth about $2,000'. Fortunately, it was discovered that large
heaps of radioactive pitchblende waste lay discarded in the
