Re: The antics of thermodynamics, the depravity of relativity, the bunkum of quantum

On Tue, 11 Mar 2025 11:47:06 +0000, Snidely wrote:

Peter Moylan blurted out:

On 11/03/25 15:05, Snidely wrote:

Thus spake Peter Moylan:
>

At the centre of the earth, you also have to taken into account the
radially directed non-gravitational  force that comes from the
weight of all the rocks (and so on) above your head.

>
Say what?  "non-graviational" from "weight"?

>
Perhaps I should have phrased that better. Consider a hypothetical cave
explorer at a distance r from the centre of the earth. The gravitational
force experienced by that person, i.e. that person's weight, is that due
to the sphere of radius r below him. The gravitational attraction
between the person and the earth is not affected by that part of the
earth at greater radii.

>
No, because the gravitational attraction between the person and the
earth is the /vector/ sum of the attraction between each part of the
person and each part of the earth, and some of those parts of the earth
are in the opposite direction of the ones below the person (and many of
in oblique direction).

..
Peter's right.  What cancels are the forces on the
person from all parts of the Earth at greater radii
than the person.  The weight of the person is due
only to the part of the Earth whose distance from
the center is less than the person's.
This is much more easily proved by Gauss's Law
(which applies to gravitation as well as to
electrostatids) than by integrating those force
vectors.
--
Jerry Friedman
--