The TimeLord wrote:

Pentcho Valev wrote in "sci.physics.relativity":

Androcles wrote:

"Pentcho Valev" <pvalev@yahoo.com> wrote in message
news:1179471503.611164.124340@o5g2000hsb.googlegroups.com...

[...]

The question:

"Does the speed of light vary in a gravitational field in accordance
with Einstein's 1911 equation c'=c(1+V/c^2) which, in the absence of a

What's the reference for this formula? As far as I know Einstein never
said this nonsense.

He did say it and it is not nonsense. Einstein's 1911 equation
c'=c(1+V/c^2) describing the variability of the speed of light is
consistent with and explains the gravitational redshift factor:

http://www.physlink.com/Education/AskExperts/ae13.cfm "So, IT IS
ABSOLUTELY TRUE THAT THE SPEED OF LIGHT IS NOT CONSTANT in a
gravitational field [which, by the equivalence principle, applies as
well to accelerating (non-inertial) frames of reference]. If this were
not so, there would be no bending of light by the gravitational field
of stars....Indeed, this is exactly how Einstein did the calculation
in: "On the Influence of Gravitation on the Propagation of Light,"
Annalen der Physik, 35, 1911. which predated the full formal
development of general relativity by about four years. This paper is
widely available in English. You can find a copy beginning on page 99
of the Dover book "The Principle of Relativity." You will find in
section 3 of that paper, Einstein's derivation of the (variable) speed
of light in a gravitational potential, eqn (3). The result is, c' = c0
( 1 + V / c^2 ) where V is the gravitational potential relative to the
point where the speed of light c0 is measured."

http://www.blazelabs.com/f-g-gcont.asp "The first confirmation of a
long range variation in the speed of light travelling in space came in
1964. Irwin Shapiro, it seems, was the first to make use of a
previously forgotten facet of general relativity theory -- that the
speed of light is reduced when it passes through a gravitational
field....Faced with this evidence, Einstein stated:"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."......Today we find that since the Special
Theory of Relativity unfortunately became part of the so called
mainstream science, it is considered a sacrilege to even suggest that
the speed of light be anything other than a constant. This is somewhat
surprising since even Einstein himself suggested in a paper "On the
Influence of Gravitation on the Propagation of Light," Annalen der
Physik, 35, 1911, that the speed of light might vary with the
gravitational potential. Indeed, the variation of the speed of light
in a vacuum or space is explicitly shown in Einstein's calculation for
the angle at which light should bend upon the influence of gravity.
One can find his calculation in his paper. The result is c'=c(1+V/c^2)
where V is the gravitational potential relative to the point where the
measurement is taken. 1+V/c^2 is also known as the GRAVITATIONAL
REDSHIFT FACTOR."