Three pieces of evidence of universe expansion support the Big Bang Theory. The first piece of evidence, which Edwin Hubble discovered, is that Response area. The second piece of evidence is the change in universal temperature. The temperature Response area . The third piece of evidence is that Cosmic Microwave Background radiation is found Response area.

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The first piece of evidence, which Edwin Hubble discovered, is that galaxies are moving away from each other at a speed proportional to their distance. This observation, known as Hubble's Law, implies that the universe is expanding.

The second piece of evidence is the change in universal temperature. In the 1960s, two physicists named Arno Penzias and Robert Wilson discovered a faint background radiation pervading the entire universe. This radiation, known as the Cosmic Microwave Background (CMB) radiation, is not associated with any specific source and is consistent with the predictions of a hot Big Bang origin.

The third piece of evidence is that the CMB radiation is found uniformly in all directions of the sky. This isotropy of the CMB supports the idea that the early universe was in a highly dense and uniform state, which is a key prediction of the Big Bang Theory.