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