What does the Expanding Universe Theory state?

• A. Edwin Hubble and fellow researchers studied and documented the movement of distant galaxies, which proved that the volume of the entire universe is expanding
• B. The universe is static
• C. The universe started at a later time
• D. The universe expands and contracts cyclically

Answer: (A)

The main idea being tested is that the universe is expanding over time, meaning space itself grows and distant galaxies move away from us. This concept comes from Edwin Hubble and his collaborators, who measured the redshift of light from distant galaxies and found that their speeds increase with distance—galaxies are receding. Those observations provide strong evidence that the cosmos is not static but expanding, which implies the observable volume of the universe has been increasing. The other ideas—that the universe is static, started later, or undergoes cycles of expansion and contraction—don’t match what Hubble’s measurements specifically show about the large-scale motion of galaxies.