  An important scientific debate took place regarding falling bodies hundreds
of years ago, and it still warrants introspection. Galileo argued that in a
vacuum all bodies fall at the same rate relative to the earth, independent of
their mass. Aristotle seemed to consider all media to be viscous, and argued
that heavier bodies fall faster. Aristotle was challenged by Philoponus, who
argued that light and heavy weights fall about equally fast in air, eleven
hundred years before Galileo. As we shall see, the problem is more subtle than
meets the eye -- even in a frictionless medium. Philoponus and Galileo are
right part of the time, and Aristotle is partly right some of the time. In fact
they are all wrong the rest of the time, with the lightest body falling fastest
when two bodies fall toward the earth. In principle the results of a free fall
experiment depend on whether falling masses originate on earth, are
extraterrestrial, are sequential or concurrent, or are simultaneous for
coincident or separated bodies, etc. When single falling bodies originate from
the earth, all bodies (light and heavy) fall at the same rate relative to the
earth in agreement with Galileo's view. Einstein's General Relativity (EGR), in
which gravity is due to space-time curvature, was motivated by the Galilean
notion that free-fall is independent of the mass and properties of a falling
body, and is just due to the properties of the milieu it finds itself in.
Quantum mechanics is found to violate the Equivalence Principle of EGR.
