I have not seen this discussed so this a question in the form of a statement for clarity. If light left a star 10 billion years ago and space has expanded for 10 billion years before the light is observed the light frequency would be stretched out or red shifted therefore some of the red shift observed would be due to distance over time. The velocity of light is constant but its speed is dependent on the gravitational field the light is in and; black holes can eject ultra high frequency gamma rays. Dark energy functions as antigravity so shifts light to lower frequency over time and space. This is only a logic question and logic creates consistency but not accuracy if the data is misinterpreted or just wrong. Considering the relatively new discovery of universal accelerating expansion of the cosmos, has the effects on red shift been questioned? If not then why not? This is just a question I asked myself and wanted some feedback. Thanks for any help.