Re: Nitpicking: gravity is not a force???

[William Beaty <billb@eskimo.com>]

On Sat, 8 Aug 1998, Jerome Epstein wrote:

> You cannot feel a (uniform) gravitational "force" (i.e. field). If a
> gravitational force is the only force acting on you, you feel
> weightless. This causes no end of confusion to students in elementary
> classes, and I have seen teachers with Ph.D's make a total shambles of
> this.
>
> The only exception would be an extremely non-uniform gravitional field
> as in falling towards the singularity of a black hole. In that case, the
> weaker field at your head as compared with your feet, causes you to be
> pulled apart by tidal forces. 

Another exception: when we take a large-scale viewpoint, Earth's radial
"field" is obvious.  For example, if my body was as large as the moon's
orbit, then Earth's field would be unmistakably radial, and I would find
it hard to remove the "field" by adopting a non-intertial reference
frame.

Another idea (don't know if it jibes exactly with GR): a positive atomic
nucleus in a parallel e-field would not experience the electrostatic
acceleration, and would feel "weightless", yet we still feel confident
in talking about electrostatic "fields".

Perhaps if our bodies were 10^8 times larger, or if micro-black-holes were
common in our environment, then the phrase "gravity field" wouldn't be
such a big source of discomfort. 


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