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Commonplace experience: If the observer were to hurry towards the
source of WATER WAVES, the observer would now pass wavecrests more
frequently than the resting observer. That is, moving observer finds
both the frequency and the speed of the wave to have increased (while
the WAVELENGTH - THE DISTANCE BETWEEN CRESTS - HAS REMAINED CONSTANT).

Three possible statements about LIGHT:

(A) (Einstein should not rule): "If the observer were to hurry towards
the source of the light, the observer would now pass wavecrests more
frequently than the resting observer. That means that, in analogy with
the water wave case, moving observer finds both the frequency and the
speed of light to have increased (while the WAVELENGTH - THE DISTANCE
BETWEEN CRESTS - HAS REMAINED CONSTANT)."

(B) (Einstein still rules but things get dangerous since an analogy
frequently used in textbooks - between water waves and light waves -
is explicitly rejected): "If the observer were to hurry towards the
source of the light, the observer would now pass wavecrests more
frequently than the resting observer. That would mean that moving
observer would find the frequency of light to have increased (but, in
contrast with the water wave case, he would find the speed of light to
have remained constant and the WAVELENGTH - THE DISTANCE BETWEEN
CRESTS - TO HAVE DECREASED)."

http://www.pitt.edu/~jdnorton/teaching/HPS_0410/chapters/big_bang/index.html
(C) (Einstein is to rule forever; the analogy between water waves and
light waves is only implicitly rejected): John Norton: "Here's a light
wave and an observer. If the observer were to hurry towards the source
of the light, the observer would now pass wavecrests more frequently
than the resting observer. That would mean that moving observer would
find the frequency of the light to have increased (AND CORRESPONDINGLY
FOR THE WAVELENGTH - THE DISTANCE BETWEEN CRESTS - TO HAVE
DECREASED)."

Pentcho Valev
pvalev@yahoo.com