How convincing are alternate explanations of galactic red shift such as the Shapiro effect?

Question

How unified are cosmolgists in accepting an expanding universe? I have also read that gravitational effects in the centre of certain galaxies might account for red shift.

Answer 1

No very.

The Shapiro delay has shown that an intense gravational field can "Slow down" light, however, the effect is very small, not great enough to affect red shift data.

Notice, I had slow down in quotes, becuase it does not actually slow the speed of light, however, an intense gravational field will affect time (as predicted by Einstein) and it will take longer for a radar wave (or light wave) to go to Venus and back (as demonstaed in the 1960s). However the delay does not affect red shift.

"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. Now we might think that as a consequence of this, the special theory of relativity and with it the whole theory of relativity would be laid in the dust. But in reality this is not the case. We can only conclude that the special theory of relativity cannot claim an unlimited domain of validity ; its results hold only so long as we are able to disregard the influences of gravitational fields on the phenomena (e.g. of light)." - Albert Einstein (The General Theory of Relativity: Chapter 22 - A Few Inferences from the General Principle of Relativity)

As you can see, even Einstein allowed for a change in the speed of light in a gravational field.

Answer 2

Halton Arp's ideas about anomolous and quantised red shifts have never been widely accepted, and the evidence increasingly shows that he was wrong. Scientists will always try and find alternate explanations for everything, but there's very strong agreement on the idea of an expanding universe.

Answer 3

There is mounting evidence that the conventional explanation of red shift being a 'doppler' effect is not correct.
Galaxies have been found with very different red shifts but with evidence that they are physically connected.
Halton Arp has published on the matter.
See also http://www.googlesyndicatedsearch.com/u/creationontheweb?hl=en&ie=UTF-8&sa=X&oi=spell&resnum=0&ct=result&cd=1&q=redshift&spell=1