Polar anisotropy of CMB

gvgomez

This discussion highlights an important issue. But the contradiction does not concern the
cosmological principle, as profgemelli still believes, but the anisotropy of light. The dipole anisotropy is interpreted in a natural way in terms of Doppler effect due to a source in motion relative to us, which is really a version of the Michelson experiment. It 'true that so far noone could ever deniedy the results of Michelson, but the CMB is an experiment as big as the universe and that has lasted billion years, it is obvious that it can show effects that our interferometers cannot see. I'm sorry for Einstein, but the ether, unfortunately, seems to exist.

cepheid

You seem to be confusing two different effects. There is the Doppler effect (relative motion between source and observer changes the observed frequency of light), and then there is the effect that Michelson was hoping to see in his interferometer, which is that relative motion between source and observer would change the observed speed of light (which would in turn change the optical path difference between two arms of an interferometer). These are two different effects. What Einstein was saying was that the speed of light observed would be independent of relative motion between source and observer. He was not denying that Doppler shifts occur. The latter is a consequence of the wave nature of light of which he was well aware.

EDIT: Another way of putting it: the motion of Earth relative to the CMB rest frame is NOT a version of the Michelson experiment, unlike what you have claimed above.

Imax

It’s unlikely under special or general relativity.
Agree :)

profgemelli

Thank you, to everybody. Your answers were useful and sometimes enlightening to me, and always were conforting to me (but that of gvgomez). I must confess I still have some residual suspicion about dipole anosptropy, which maybe I will try to better focus, but I now certainly feel more confortable with it. Thank you.