eliminating geometrical and physical optics you wrote above when describing redshift mechanisms we need to eliminate geometrical and physical optics i note that you've included the wolf effect which is consistent with your statement the article on the wolf effect includes reliable sources stating that the wolf effect is a redshift mechanism can you provide a source that indciates that the wolf effect should be excluded as you stated i understand that many books might not include it for whatever reason but this is not the same as excluding it or how about a source excluding physical optics from redshift mechanism