Re: Bending of light not well authenticated

Hi Gene et al...

Gene McGraw wrote:
> On 22 May 2005 "Ken S. Tucker" wrote:
> >> At the perihelion r = R we have dr/dt = 0. Insert this into the
> >> equation of motion
> >> (dr/dt)^2 / c^2 = (1 - 2 U)^2 (1 - (1 - 2 U) b^2 / r^2)
> >Does that come from Schwarz...? If so give a hint how.
>
> The complete derivation of the equations of motion can be found at
> www.mathpages.com/rr/s6-03/6-03.htm

Yeah Yeah Yeah

> >Consider when M=0 then the spacetime field is Cartesian and the
> >Cartesian Radius R^2 = X^2 + Y^2 + Z^2 holds, and there is a
> >*direction* where dR/dt=0 at the closest approach to the M=0 point.
> >That direction from "M" could be aligned with a distant star.
> >When M>0 the deflection in that aligned *direction* is now
> >dr/dt= -2M/R...
>
> No, dr/dt is not a direction,

You evidently did not understand what I wrote,
please re-read.

>it is the derivative of the radial
> coordinate with respect to the time coordinate along the path, and it
> is zero at the point of closest approach to the origin. This is true
> regardless of whether there is mass at the origin. This is simple
> grade-school geometry.

Anyone who tries to claim light deflection in GR
is mere "grade-school" is likely over-simplfying.

> In the presence of a gravitating mass M, the paths of light have a
> certain (hyperbolic) shape, and the curvature of this hyperbola
> depends on the mass M and on how close the path comes to the
> mass, i.e., on the distance of closest approach, which is R. The
> shapes of the paths are found by determining the light-like geodesics
> through spacetime. The equations of motion define these shapes.
> Once you have determined these equations, you simply need
> to plug in the mass M of the gravitating body, and the perihelion
> distance R of the path you are interested in, and the equations of
> motion give you the amount of deflection.

bla bla, ok we agreed to that....

> >where "r" is in terms of a new CS that *contracts* the Cartesian
> >"R", thus defining the meaning of dr/dt.
>
> No, that does NOT define the meaning of dt/dt. The meaning of dr/dt
> is the derivative of r with respect to t along the subject path. The
> "meaning" that you are trying to assign to "dr/dt" is simply childish
> nonsense. You seem to be fantasizing that dr signifies a change in
> the distance of closest approach of a particular ray of light to the
> origin when a mass M is suddenly placed at the origin. That is NOT
> what dr/dt represents.
>
> The rest of your post is just more gibberish. For example, you say
>
> >and of course dR/dt = 1,
>
> Utterly non-sensical.

> >That's a fast and cheap way to go from the Schwarz...to
> >deflection 2M/R and integrated contraction r=R-2M.
>
> No, that's a monkey trying to mimic the activities of a human, but
> with no conception that words and symbols have meanings.

Gene gets - spit balls aside - Newtons prediction,
i.e. 1/2 the result AE get's as I (Ken) demo'd.
I think this is a good lesson on why we should take
care not to rush into conclusion with half the facts.
Gene's approach look's good superficially, however
his underestimation of the problem yields results
different from reality.
I suspect he'll argue forever he's right and we're
all wrong...too bad, looked like he was above idiot.
Ken

.

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