Which of the following statements about the universe is true based on current scientific theories?

The statement that the universe is expanding is supported by a significant body of observational evidence and is a key aspect of modern cosmology. This conclusion stems from various observations, such as the redshift of distant galaxies, which indicates that they are moving away from us. This phenomenon was first observed by Edwin Hubble and led to the formulation of Hubble's Law, which quantifies the relationship between the distance of galaxies and their recessional velocity.

Additionally, the expansion of the universe is consistent with the Big Bang theory, which describes the universe's origin and subsequent expansion from an incredibly hot, dense point. Current measurements also indicate that this expansion is accelerating due to the influence of dark energy, a mysterious force that constitutes a significant portion of the universe's energy density.

The other statements do not align with current scientific understanding; for instance, the universe is not only 1 billion years old, nor is it getting denser overall, as the expansion leads to a decrease in density, and the concept of a finite and unchanging universe contradicts the observational evidence of expansion.