"Pentcho Valev" wrote in message
...
An excerpt from COSMIC HORIZONS: ASTRONOMY AT THE CUTTING EDGE, edited
by Steven Soter and Neil deGrasse Tyson, a publication of the New
Press. © 2000 American Museum of Natural History. To order the book,
call 1-800-233-4830, or go to
http://www.amnh.org/education/resour...l/web/buybook/

http://www.amnh.org/education/resour...s_michell.html
"Michell accepted Newton's theory that light consists of small
material particles. He reasoned that such particles, emerging from the
surface of a star, would have their speed reduced by the star's
gravitational pull, just like projectiles fired upward from the Earth.
(...) Michell got the right answer, although he was wrong about one
point. We now know, from Einstein's relativity theory of 1905, that
light moves through space at a constant speed, regardless of the local
strength of gravity."

Needless to say, in 1905 Einstein did not say anything like "light
moves through space at a constant speed, regardless of the local
strength of gravity".

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So far that is correct, as far as I know.


Rather, from 1907 on, he claimed that, in a
gravitational field, the speed of light is VARIABLE, not constant.

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I actually doubt that Einstein would have said that, as it is so simplictic
as to be false.

Specifically, an observer can be in as strong a gravitational field as you
like, but as long as the observer is in an intertial reference frame (eg in
orbit), they will always measure the local speed of light as c.

Have you a cite to Einstein's exact words?