🚀 go-pugleaf

Pentcho Valev wrote on Thu, 21 May 2009 22:01:51 -0700:

(...)

> The correct answer "redshift is due to change in the speed of light"
> will have to be officially adopted soon:

It depends of the theory used. In flat spacetime theories of gravity the
physical speed of light is not c but depends on gravitation.

> http://www.blazelabs.com/f-g-gcont.asp "So, faced with this evidence
> most readers must be wondering why we learn about the importance of the
> constancy of speed of light. Did Einstein miss this? Sometimes I find
> out that what's written in our textbooks is just a biased version taken
> from the original work, so after searching within the original text of
> the theory of GR by Einstein, I found this quote: "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 results hold only so long as we are able to disregard the
> influences of gravitational fields on the phenomena (e.g. of light)." -
> Albert Einstein (1879-1955) - The General Theory of Relativity: Chapter
> 22 - A Few Inferences from the General Principle of Relativity-.

There was recent threads both in sci.physics.foundations and in
sci.physics.research where this book from Einstein was discussed.
Basically, Einstein gave an unphysical (in GR sense) speed for light
signals from misconceptions based in his 1911 theory with variable light
over flat spacetime.

Moreover, that unphysical GR speed was defined by Einstein in the sense of
Euclidean geometry, even when he recognized that Euclidean geometry do not
hold even at first approximation in GR formalism for bending!

As illustrated in my blog, in GR light deflection is due to curvature of
spacetime:

http://3.bp.blogspot.com/_I-n4UWp0ZqM/RsmMDkc5CjI/AAAAAAAAAEU/EdXg-C5_-Fo/
s400/curvedspacetime.gif

As illustrated in my blog, in flat spacetime theories, light deflection is
due to gravitational changes in the speed of light (photons couple to
gravitational field via its EMT):

http://4.bp.blogspot.com/_I-n4UWp0ZqM/RsmMD0c5CkI/AAAAAAAAAEc/joqIPrW5O-k/
s400/flatspacetime.gif

He did other mistakes, for instance he computed light bending using that
unphysical GR speed and concluded that a half of bending was due to
Newtonian field and another half due to curved space. As explained in
cited groups this is not true, the entire 2phi (not phi) factor is related
to deviation from flatness.

Of course in flat spacetime theories the speed of ligh varies with
gravitation. E.g. at lowest order

v = c (1 + 2phi/c^2)

And this gives exactly light bending and other tested results.





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