DOPPLER EFFECT (MOVING OBSERVER): VARYING OR CONSTANT WAVELENGTH?

On Monday, October 1, 2012, Tom Roberts wrote in sci.physics.relativity:
Wavelength is not an intrinsic property of light, so it cannot be

discussed independent of how it is measured. But it is clear that in vacuum the

light ray itself is unchanged as it propagates.



Differently moving observers will measure different wavelengths for a given

light ray, because their MEASURING INSTRUMENTS are oriented differently in

spacetime, and such a measurement inherently PROJECTS the light ray onto the

measuring instrument.

Honest Roberts,

Do you mean that the orientation of the MEASURING INSTRUMENT varies with the speed of the observer? This orientation remains unchanged so long as the speed of the observer remains constant?

Yes or no, Honest Roberts?

Pentcho Valev

Stephen Hawking contradicts Tom Roberts: Wavelength is an INTRINSIC property - it can already be changed before the interaction with the observer:

http://www.amazon.com/Brief-History-.../dp/0553380168
Stephen Hawking, "A Brief History of Time", Chapter 3: "...we must first understand the Doppler effect. As we have seen, visible light consists of fluctuations, or waves, in the electromagnetic field. The wavelength (or distance from one wave crest to the next) of light is extremely small, ranging from four to seven ten-millionths of a meter. The different wavelengths of light are what the human eye sees as different colors, with the longest wavelengths appearing at the red end of the spectrum and the shortest wavelengths at the blue end. Now imagine a source of light at a constant distance from us, such as a star, emitting waves of light at a constant wavelength. Obviously the wavelength of the waves we receive will be the same as the wavelength at which they are emitted (the gravitational field of the galaxy will not be large enough to have a significant effect). Suppose now that the source starts moving toward us. When the source emits the next wave crest it will be nearer to us, so the distance between wave crests will be smaller than when the star was stationary. This means that the wavelength of the waves we receive is shorter than when the star was stationary. Correspondingly, if the source is moving away from us, the wavelength of the waves we receive will be longer. In the case of light, therefore, means that stars moving away from us will have their spectra shifted toward the red end of the spectrum (red-shifted) and those moving toward us will have their spectra blue-shifted."

Pentcho Valev

On Oct 4, 1:15*pm, Pentcho Valev wrote:
Stephen Hawking contradicts Tom Roberts: Wavelength is an INTRINSIC property - it can already be changed before the interaction with the observer:

http://www.amazon.com/Brief-History-.../dp/0553380168
Stephen Hawking, "A Brief History of Time", Chapter 3: "...we must first understand the Doppler effect. As we have seen, visible light consists of fluctuations, or waves, in the electromagnetic field. The wavelength (or distance from one wave crest to the next) of light is extremely small, ranging from four to seven ten-millionths of a meter. The different wavelengths of light are what the human eye sees as different colors, with the longest wavelengths appearing at the red end of the spectrum and the shortest wavelengths at the blue end. Now imagine a source of light at a constant distance from us, such as a star, emitting waves of light at a constant wavelength. Obviously the wavelength of the waves we receive will be the same as the wavelength at which they are emitted (the gravitational field of the galaxy will not be large enough to have a significant effect). Suppose now that the source starts moving toward us. When the source emits the next wave crest it will be nearer to us, so the distance between wave crests will be smaller than when the star was stationary. This means that the wavelength of the waves we receive is shorter than when the star was stationary. Correspondingly, if the source is moving away from us, the wavelength of the waves we receive will be longer. In the case of light, therefore, means that stars moving away from us will have their spectra shifted toward the red end of the spectrum (red-shifted) and those moving toward us will have their spectra blue-shifted."

Pentcho Valev

Do we have any objective proof that individual photons actually travel?