First, let me apologize to Joel, Jim and Leigh if at times I was overly
contentious on this subject. I am not usually this way except with family.
Now, let me give my thoughts.
First, I refer to Leigh's reference to "A Textbook of the Principles of
Physics" by Alfred Daniell, Macmillan & Co, New York and London, 1894, but
only as it pertains to weight.
"The weight of a certain quantity of matter depends upon the presence and
nearness of other matter, which attracts it according to the well-known law
of Gravitation. This may, and even within our terrestrial observation, does
vary; the effect of gravity on a given mass - that is to say, its Weight - is
greater as we near the poles than it is at the equator; and the weight of a
substance varies, therefore, according to local causes, while the quantity of
matter in it remains the same."
This 1894 definition is clear to me. Weight is the force of gravity and not
limited to Earth and objects on the Earth. It is consistent, as Leigh says,
with most physics text books that I have read. I do not see any reason to
alter this definition.
Here is a quotation from "Physics" by Resnick, Halliday & Krane, 4th Ed.,
John Wiley & Sons INC., 1992, pertaining to Cavendish's experiment.
"For this reason Cavendish is said to have been the first person to "weigh"
the Earth. (In fact, the title of the paper written by Cavendish describing
his experiments referred not to measuring G but instead to determining the
density of Earth from its weight and volume.)"
Hence, weight, which I am interpreting as meaning the force of gravity by
Cavendish, has been used for at least two hundred years. Am I incorrect in
this interpretation? I read through the accounts of Cavendish's experiment
in "Great Experiments in Physics" by Shamos. However, while this text gave
the experimental data and the concluding density of the earth, it did not
show Cavendish's calculations.
Some have advocated not using weight at all, but instead, advocate saying the
force of gravity. I say weight is the force of gravity. Would those
advocating not using weight also advocate not using acceleration, but instead
always say the time rate of change in velocity?
Others have advocated redefining weight as the force a scale reads. I see
nothing in the definition, weight is the force of gravity, regarding scales.
While scales may be properly used to measure weight, they are not necessary
(and not included) in its definition.