🚀 go-pugleaf

"Pentcho Valev" <pvalev@yahoo.com> wrote in message 
news:e2a48506-5a3f-4077-901b-f87542dd785e@j8g2000yql.googlegroups.com...
On Apr 9, 10:33 pm, Tom Roberts <tjroberts...@sbcglobal.net> wrote in
sci.physics.relativity:
> bill wrote:
> > A person is located on a mountain top and is looking at a (very large)
> > clock (B) at sea-level.
> > He notices that clock B is ticking over at a slower rate than his own
> > clock (A) as theorized by Einstein in general theory and as ratified
> > by the Wallops Island experiment where a clock at sea-level, being
> > located in a strong gravitational tidal area, will tick over at a
> > slower rate than an identical clock on top of a mountain that is in a
> > weaker gravitational tidal area.
>
> Note that what you call "gravitational tidal area" is really called
> "Newtonian gravitational potential", valid in the Newtonian
> approximation to GR. Indeed, tidal forces/effects are not involved
> (tidal forces are second derivatives of the Newtonian potential).
>
> Note that while A _SEES_ B tick at a slower rate, this does not imply
> that clock B actually ticks at a slower rate than clock A. Indeed, in GR
> this is modeled as an artifact of the COMPARISON [#], not as an effect
> or modification of the clocks themselves: both clocks tick at their
> usual (proper) rates, but their tick rates appear different when
> situated and compared as you describe.
>
> [#] This comparison is via EM signals in curved spacetime.
>
> > Is he entitled to be of the opinion that if he were to move to sea-
> > level his clock would be subjected to the same 'law' of physics thus
> > it will then be ticking over at a slower rate than it is before he
> > starts his descent?
>
> No. See above -- this is not an effect ON THE CLOCKS, but rather OF THE
> COMPARISON. Note that he is entitled to expect that if he carries his
> clock down and puts it right next to B that the two clocks will tick at
> the same rate.
>
> Your statements are expressed with the implicit assumption there there
> is some "global", "universal", or "absolute" way to determine a clock's
> tick rate. In GR there is no such thing -- all you can do is compare
> clocks to other clocks; the method of comparison can, and usually does,
> affect the result.
>
> Tom Roberts

: Honest Roberts, your cleverer brothers Einsteinians expose the
: "artifact of the COMPARISON" in a somewhat clearer way:

: http://www.people.fas.harvard.edu/~djmorin/book.html
: Chapter 14: "The equivalence principle has a striking consequence
: concerning the behavior of clocks in a gravitational field. It implies
: that higher clocks run faster than lower clocks. If you put a watch on
: top of a tower, and then stand on the ground, you will see the watch
: on the tower tick faster than an identical watch on your wrist. When
: you take the watch down and compare it to the one on your wrist, it
: will show more time elapsed."

: However, Honest Roberts, even your cleverer brothers Einsteinians
: would never answer the following question:

: Is the "artifact of the COMPARISON" (that is, gravitational time
: dilation) consistent with Einsteiniana's dicovery that the speed of
: light is CONSTANT in a gravitational field,

Both are nonsense. Einstein's discovery was just the contrary in both cases:

1. "Thus the clock goes more slowly if set up in the neighbourhood of 
ponderable masses. From this it follows that the spectral lines of light 
reaching us from the surface of large stars must appear displaced towards 
the red end of the spectrum."
- http://www.alberteinstein.info/gallery/pdf/CP6Doc30_English_pp146-200.pdf 
(p.198)

2. "according to the general theory of relativity, the law of the constancy 
of the velocity of light in vacuo, which constitutes one of the two 
fundamental assumptions in the special theory of relativity and to which we 
have already frequently referred, cannot claim any unlimited validity"
- http://www.bartleby.com/173/22.html
- see also the same p.198 of the first ref. for details.

: or is it consistent with
: Einsteiniana's discovery that the speed of light is VARIABLE in a
: gravitational field and obeys e.g. Einstein's 1911 equation c'=c(1+gh/
: c^2) given by Newton's emission theory of light?

You should instead refer to his corrected equations of 1916 - which are NOT 
given by Newton's theory.

Good luck.
Harald