Isn't the reason the sky isn't bright at night ,due to all the stars, because the fact the stars aren't bright enough to be seen by the naked eye after a certain distance? So it doesn't necessarily depend on the fact the universe doesn't have to be infinite or expanding? I know the intensity of light decreases due to the inverse square law and I know that there would be a minimum level of brightness, as light is quantised, that would never be lower but would happen less frequent as the photons would be less frequent. But our eyes aren't that sensitive so eventually we would not see anything in terms of visible light.
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