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number of light sources in the universe increases as r3 (r is the distance from us) while their intensities decrease as r2 only.
Would light be deadly without gravity to change its wavelength?
Ah... so the question may have been asking about Olber's Paradox?In this case, it is the expansion of the universe which red-shifts the light from distant galaxies, and makes the Earth habitable.The Cosmological red-shift has a larger impact on light from distant galaxies than does the Einstein (gravitational) red-shift of those same galaxies (or their stars).
Quote from: jeffreyHWould light be deadly without gravity to change its wavelength?No. The change in wavelength is imperceptible. I.e. the change in energy is so small as to not be noticeable or to make a difference.