Educators in Einsteiniana's schizophrenic world often teach variable-
speed-of-light "heresies" that additionally confuse believers' minds
and make the true antithesis (the equation c'=c+v given by Newton's
emission theory of light) of Einstein's 1905 false constant-speed-of-
light postulate invisible:

http://edge.org/conversation/loop-qu...ity-lee-smolin
Lee Smolin: "Now, here is the really interesting part: Some of the
effects predicted by the theory appear to be in conflict with one of
the principles of Einstein's special theory of relativity, the theory
that says that the speed of light is a universal constant. It's the
same for all photons, and it is independent of the motion of the
sender or observer. How is this possible, if that theory is itself
based on the principles of relativity? The principle of the constancy
of the speed of light is part of special relativity, but we quantized
Einstein's general theory of relativity. Because Einstein's special
theory is only a kind of approximation to his general theory, we can
implement the principles of the latter but find modifications to the
former. And this is what seems to be happening! (...) We have since
written several papers together showing how Einstein's postulates may
be modified to give a new version of special relativity in which the
speed of light can depend on energy."

Pentcho Valev