Stuf4 wrote:
From Mike Hanson:

(Stuf4) wrote


snip

- Gravity is *distinctly different* from acceleration.

While gravity has a property of acceleration, it is *not*
acceleration. A 'g' is a unit of acceleration standardized upon a
particular case of acceleration due to gravity (the gravitational
acceleration at the surface of the Earth).

snip

I haven't posted here for a while. Decided to take a look, saw an
interesting-looking thread title, and came across the above statement.
You appear to have mangled your terms somewhat:

*Gravitation* is distinctly different from acceleration.

Gravity, however, is locally *indistinguishable* from acceleration.
That this is so led Einstein to apply Occam's razor and postulate that
they are one and the same phenomenon, leading to general relativity.
And since GR has yet to be falsified, one can say that, to the best of
our knowledge, gravity and acceleration are indeed the same thing (and
hence that NASA is correct in its use of the letter g).


This point regarding the equivalence theory has been addressed more
than once on this thread...

One easy way to determine whether you are accelerating due to gravity
or not is to look out the window of your spacecraft to see if there
are any stars or planets nearby.

(I've suggested elsewhere that the root of this confusion in
terminology is a misunderstanding of the equivalence principle.)


~ CT

Note...I recently posted a reply pointing out that the Principle of
Equivalence is *not* rooted in an equivalence between inertial and
gravitational mass. Rather, it comes from the equivalence of inertial
reference frames...those that are accelerating or equivalent to those in
a gravitational field. Also, the nature of inertial mass is not fully
understood and it is only postulated that inertial and gravitational
mass are the same. Experiments carried out show this to be so to within
great precision, but not infinite precision.