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Do we know if light is red-shifted by traveling through space? If it isn't, how do we know? I guess my pondering has lead me to wonder if the observed accelerating space-expansion is a misinterpretation. If light is red-shifted by traveling through space, we may be able to re-interpret Hubble's equation (I know, that might be heresy) as
$redshift = SomeConstant*d$ which would imply that distant objects aren't necessarily accelerating, the light we view is increasingly redshifted for more distance objects, independent of them moving away from us. Then, maybe we don't need dark energy anymore.?.