Archimedes was a Greek
scientist, mathematician, and inventor who lived in Syracuse
(Sicily)
from 287-212 BC.
Archimedes may have discovered his principle of
buoyancy while trying to solve a problem given to him by the King
of
Syracuse. King Hiero had ordered a local tradesman to design
and
fabricate a gold crown to be set up in a shrine as an offering to
the
gods. The artisan was given a precise amount of gold for the
project and returned, sometime later, with a crown of identical
weight. The King appeared to be entirely satisfied until
word
reached him later that the artist may have replaced some of the
gold
with silver during the manufacture of the crown. The King
turned
to Archimedes for help. Archimedes probably realized that,
because gold has a density (18.9 g/cm3) almost twice
that of
silver
(10.5 g/cm3), a crown made out of gold and silver would
have a larger
volume than a crown made out of pure gold.
Archimedes may also
have used his principle of buoyancy to actually measure the
density of
the crown (a mixture of gold and silver would have a density less
than
pure gold). Unfortunately I haven't found out whether the
crown
turned out to be pure gold or whether the tradesman had tried to
cheat
the King.