Bethany and Joquin are discussing theories about the universe. Bethany believes that since the beginning of the universe, galaxies have been moving, and will continue to move, toward Earth. Joquin argues that galaxies have been moving away from Earth.

Redshift is the stretching of light toward longer, redder wavelengths when a galaxy moves away from an observer. Observations of redshift in distant galaxies support Joquin’s claim that galaxies are moving away from Earth. Nucleosynthesis, the cosmic microwave background, and the composition of stars are not measurements of galaxy motion.

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