The Doppler Effect

What does the fact that most galaxies are seen with a red shift mean to astronomers?

The fact that astronomers observe most of the galaxies in the universe as having a red shift means that overall, galaxies are moving away from our galaxy, the Milky Way. This can only be happening if the universe as a whole is expanding. The expansion of the universe led to the development of the big bang theory of the universe’s creation.


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