Two years after the introduction of his famous principle of constancy
of the speed of light ("...light is always propagated in empty space
with a definite velocity c which is independent of the state of motion
of the emitting body") Einstein realized that, =A0in the presence of a
gravitational field, the speed of light VARIES and can become GREATER
THAN c=3D300000km/s. It was not difficult for Einstein to see that, once
the constancy of the speed of light is broken in the presence of a
gravitational field, it is ABSOLUTELY broken, that is, it cannot be
"independent of the state of motion of the emitting body". The
subsequent development of the theory of relativity can be
characterized as a mixture of camouflage, lies, red herrings, hints,
semi-confessions, full confessions:

http://www.pitt.edu/~jdnorton/papers/OntologyOUP_TimesNR.pdf"What Can
We Learn about the Ontology of Space and Time from the Theory of
Relativity?", John D. Norton: "In general relativity there is no
comparable sense of the constancy of the speed of light. The constancy
of the speed of light is a consequence of the perfect homogeneity of
spacetime presumed in special relativity. There is a special velocity
at each event; homogeneity forces it to be the same velocity
everywhere. We lose that homogeneity in the transition to general
relativity and with it we lose the constancy of the speed of light.
Such was Einstein's conclusion at the earliest moments of his
preparation for general relativity. ALREADY IN 1907, A MERE TWO YEARS
AFTER THE COMPLETION OF THE SPECIAL THEORY, HE HAD CONCLUDED THAT THE
SPEED OF LIGHT IS VARIABLE IN THE PRESENCE OF A GRAVITATIONAL FIELD;
indeed, he concluded, the variable speed of light can be used as a
gravitational potential."

http://www.logosjournal.com/issue_4.3/smolin.htmLee Smolin: "Quantum
theory was not the only theory that bothered Einstein. Few people have
appreciated how dissatisfied he was with his own theories of
relativity. Special relativity grew out of Einstein's insight that the
laws of electromagnetism cannot depend on relative motion and that the
speed of light therefore must be always the same, no matter how the
source or the observer moves. Among the consequences of that theory
are that energy and mass are equivalent (the now-legendary
relationship E =3D mc2) and that time and distance are relative, not
absolute. SPECIAL RELATIVITY WAS THE RESULT OF 10 YEARS OF
INTELLECTUAL STRUGGLE, YET EINSTEIN HAD CONVINCED HIMSELF IT WAS WRONG
WITHIN TWO YEARS OF PUBLISHING IT."

Albert Einstein, "Relativity", Chapter 22: "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."

http://www.hawking.org.uk/lectures/dice.htmlStephen Hawking: "Both
Mitchell and Laplace thought of light as consisting of particles,
rather like cannon balls, that could be slowed down by gravity, and
made to fall back on the star. But A FAMOUS EXPERIMENT, carried out by
two Americans, MICHELSON AND MORLEY in 1887, SHOWED THAT LIGHT ALWAYS
TRAVELLED AT A SPEED OF ONE HUNDRED AND EIGHTY SIX THOUSAND MILES A
SECOND, NO MATTER WHERE IT CAME FROM."

http://philsci-archive.pitt.edu/archive/00001743/02/Norton.pdfJohn
Norton: "Einstein regarded the Michelson-Morley experiment as evidence
for the principle of relativity, whereas later writers almost
universally use it as support for the light postulate of special
relativity......THE MICHELSON-MORLEY EXPERIMENT IS FULLY COMPATIBLE
WITH AN EMISSION THEORY OF LIGHT THAT CONTRADICTS THE LIGHT
POSTULATE."

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' =3D c0
( 1 + V / c2 ) where V is the gravitational potential relative to the
point where the speed of light c0 is measured."

Einstein (letter to a friend): "If the speed of light is the least bit
affected by the speed of the light source, then my whole theory of
relativity and theory of gravity is false."

Einstein (at the end of his life): "I consider it quite possible that
physics cannot be based on the field concept, i.e., on continuous
structures. In that case, nothing remains of my entire castle in the
air, gravitation theory included, [and of] the rest of modern
physics."

Pentcho Valev