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Re: g

(Fun thought experiment: what would happen if you release a -1kg ball? Both the
gravitational mass and inertial mass are negative. Your immediate response
probably isn't correct.)

John E. Gastineau

Not necessarily. Gravitational and inertial mass have logically
independent definitions -- inertial in terms of the inertial response
of an object subject to any force (how much acceleration do you get?)
and gravitational in terms of the gravitational force that an object
experiences. These are OBSERVED to be the same ( which is a version
of the Equivalence Principle) but there is no theoretical principle
REQUIRING them to be the same. It is perfectly plausible, and
probably preferable, to imagine a universe in which gravity behaves
differently but inertia is what it always has been (whatever that
is). Reversing the gravitational mass does not necessarily imply
reversing the inertial mass as well -- those are separate postulates.
Which makes it an even better thought experiment. Cool.

Paul J. Camp "The Beauty of the Universe
Assistant Professor of Physics consists not only of unity
Coastal Carolina University in variety but also of
Conway, SC 29526 variety in unity. --Umberto Eco
(803)349-2227 The Name of the Rose
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