The redshift of galaxies in the Universe is correctly interpreted as:
A: A Doppler shift due to the motions of galaxies through space.
B: An "aging" of the light.
C: Space itself expanding with time; the photon wavelengths are stretched as they they travel through space.
D: The difference in temperature of distant and nearby galaxies.
E: Extinction due to the effects of dust in galaxies.
Ans: C: Space itself expanding with time; the photon wavelengths are stretched as they they travel through space.
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