🚀 go-pugleaf

On Mar 24, 3:12 am, xxein <xx...@comcast.net> wrote:
> On Mar 23, 10:23 am, Pentcho Valev <pva...@yahoo.com> wrote:
>
> > http://www.bartleby.com/173/22.html
> > Albert Einstein: "In the second place our result shows that, 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. A curvature of rays of light can only take place when the
> > velocity of propagation of light varies with position. Now we might
> > think that as a consequence of this, the special theory of relativity
> > and with it the whole theory of relativity would be laid in the dust.
> > But in reality this is not the case. We can only conclude that the
> > special theory of relativity cannot claim an unlimited domain of
> > validity; its result hold only so long as we are able to disregard the
> > influences of gravitational fields on the phenomena (e.g. of light)."
>
> > There is a trivial truth Einstein uses in this case: the speed of
> > light "varies with position" in a gravitational field but, in the
> > absence of a gravitational field or in a free-falling laboratory, it
> > does not vary with position and IN THIS SENSE is constant. However
> > Einstein knows that in Einstein zombie world constancy in any sense
> > could easily become constancy in the sense of Einstein's 1905 false
> > light postulate:
>
> > http://www.fourmilab.ch/etexts/einstein/specrel/www/
> > "....light is always propagated in empty space with a definite
> > velocity c which is independent of the state of motion of the emitting
> > body."
>
> > So Einstein zombie world will never realize that the fact that the
> > speed of light "varies with position" in a gravitational field implies
> > that, in the absence of a gravitational field, it does depend on "the
> > state of motion of the emitting body" and so the 1905 light postulate
> > is violated. The intimate relationship between Einstein and Einstein
> > zombie world is nicely expressed by the Cambridge Professor John
> > Barrow:
>
> > http://www.aapps.org/archive/bulletin/vol15/15-5/15_5_p2p3%7F.pdf
> > John Barrow: "Einstein restored faith in the unintelligibility of
> > science. Everyone knew that Einstein had done something important in
> > 1905 (and again in 1915) but almost nobody could tell you exactly what
> > it was. When Einstein was interviewed for a Dutch newspaper in 1921,
> > he attributed his mass appeal to the mystery of his work for the
> > ordinary person: "Does it make a silly impression on me, here and
> > yonder, about my theories of which they cannot understand a word? I
> > think it is funny and also interesting to observe. I am sure that it
> > is the mystery of non-understanding that appeals to them...it impresses
> > them, it has the colour and the appeal of the mysterious."
>
> > Pentcho Valev
> > pva...@yahoo.com
>
> xxein: "So Einstein zombie world will never realize that the fact that
> the
> speed of light "varies with position" in a gravitational field
> implies
> that, in the absence of a gravitational field, it does depend on "the
> state of motion of the emitting body".
>
> It does not imply that at all.

A light source at the top of a tower of height h emits photons with
speed c (relative to the source). The photons accelerate so that, when
they reach a receiver on the ground, their speed (relative to the
receiver) is

c' = c(1 + gh/c^2)               /1/

which is Einstein's 1911 equation. Now a rocket with length h
accelerates with acceleration g. A light source at the front end emits
photons with speed c (relative to the source). When the photons reach
the receiver at the back end, this receiver has a speed v relative to
the light source at the moment of emission. What is the speed of the
photons, c', relative to the receiver, at the moment of reception?

You should only apply Einstein's equivalence principle and see that

gh = cv               /2/

Substitute this into /1/ and you obtain

c' = c + v                     /3/

Pentcho Valev
pvalev@yahoo.com