Question 02/00
HALLEY'S PLANET
Not so many years ago there was no order of magnitude estimate of the
age of the planet Earth. Edmund Halley (yes, that's the "comet guy") wrote an
article in Philosophical Transactions of the Royal Society of London,
29, 296 (1714),
where he observed that lakes that emit no rivers (such as Dead Sea, or
Caspian Sea) are very salty, and thus it is reasonable to assume that
rivers bring salt into the lakes. He further claimed that
"'tis not improbable that the ocean it self is become salt from
the same cause." Consequently, by measuring the salinity of the oceans
and by determining the amount of salt brought by rivers every year,
one could estimate the age of the Earth. Halley lacked the data
to actually perform an estimate of the age of the Earth using his method.
Halley's assumptions are wrong, but nevertheless it was a nice try
for his time. What would be the age of Earth according to Halley's
method?
This problem was suggested by Y. Kantor.
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