Re: Aberation and the Speed of Gravity

On Sep 14, 6:26 pm, bz <bz+...@xxxxxxxxxxxxxxxxxxxx> wrote:
"JM Albuquerque" <jmDO...@xxxxxxx> wrote innews:5l0jd8F5rl1aU1@xxxxxxxxxxxxxxxxxx:
"bz" <bz+...@xxxxxxxxxxxxxxxxxxxx> escreveu na mensagem
news:Xns99AB6666466E0WQAHBGMXSZHVspammote@xxxxxxxxxxxxxxxxx

[big snip]

However Newton's reasoning DID require 'gravity' to propagate
'instantly', because if the effects of gravity were limited in speed in
any way, stable orbits could not exist.

Yes.

Basically Ken S. Tucker described Newton's reasoning.

Newton did not propose that the force of gravity could point anywhere
other than the center of the circular orbit.

Nor did Ken s. Tucker.
Ken's point is about the speed of gravity and the results of a
finite speed.

He drew the force on a slant in relation to the tangent to the orbit. The
force can't be slanted.
bz

We're dragging "bz" into the wonderful world
of relativity, me too!
I'll try another ascii comic.

Two ships "R" and "L" are going in opposite
directions (Right & Left by coincidence :-),
pass each other at point "p" that is
perpendicular to the Newtonian position of
the Sun (S).
Now R measures the aberrated location of
the Sun at s{R} and L measures it at s{L},

------R-->p<--L-------
........../|\............
........./.|.\...........
......../..|..\..........
.......s..(S)..s.........
......{L}.....{R}.......

R and L are moving in opposite directions
in circular orbits around the Sun.
Evidently they will disagree about the
direction of Sun when each is a "p".

((I suppose we could lift the requirement
of R and L being in circular orbits, and
instead calculate for a fast hyperbolic
fly-by, but that's a complication)).

My understanding is that GR allows each
FoR (R and L in this case) to use their
own measurements to determine the Laws of
Physics as they apply to their individual
CS's. (FoR is Frame of Reference).
That also means "p" is NOT a prefered FoR.

So when "bz" says "force can't be slanted"
it's rather like denying the fact of the
aberration of the Sun's position.

I see (demo'd mathematically) the geodesic
to be versatile enough to accommodate the
differences in the measurement of the Sun's
location, relative to R and L at the same
point "p" using the Sun's apparent location.
It follows, the "Velocity of Gravity" and
the "Velocity of Light" are equal in GR.

Does that sound ok?
Regards
Ken S. Tucker

.

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