We know that the study of geometry goes back at least four thousand years, as far
back as the Babylonians (2000 to 1600 BC). Their geometry was empirical, and limited
to those properties physically observable. Through their measurements they approximated
the ratio of the circumference of a circle to its diameter to be 3, an error of less
than five percent. They had knowledge of the Pythagorean Theorem, perhaps the most
widely known of all geometric relationships, a full millennium prior to the birth of
Pythagoras.