How does the redshift of galaxies provide evidence that the universe is expanding?

The redshift of galaxies refers to the phenomenon where the light from distant galaxies shifts toward the red end of the spectrum, indicating that they are moving away from us. This observation, first noted by Edwin Hubble, suggests that the universe is expanding, as galaxies are not just receding from Earth but from each other. The greater the redshift, the faster a galaxy is moving away, supporting the idea that space itself is stretching. This relationship is encapsulated in Hubble's Law, which quantifies the expansion rate of the universe.