According to the Bible, the universe had a beginning, so it is not eternal. Scientific and philosophical arguments confirm that the universe had a beginning.
Genesis 1:1 tells us that God created the heavens and the earth. This marked the beginning of space, time, and matter as we know it. Nothing, aside from God the eternal creator, existed “before” creation. Since it had a beginning, the universe cannot be eternal. Revelation 21:1 says that one day God will create a new heaven and new earth (a new universe), thus ending this age. Several independent lines of scientific evidence confirm that the universe had a beginning. However, scientists do not know for certain when or how the universe began or will end. Various theories and scenarios have been proposed, but none have been proven. All evidence points to a created universe. Biblically, scientifically, and philosophically speaking, we have confidence that the universe is not eternal. It had a beginning and will also have an end.
The concept of an eternal (always having existed and always will exist) universe is attributed to Greek philosophers such as Aristotle, who believed the universe was beginning-less and unchanging. On the other hand, St. Augustine argued that God created the universe "ex nihilo" (from nothing), meaning time and the universe itself had a beginning, so the universe could not be eternal. The dominant non-Christian view was that of an eternal universe, until the development of the Big Bang theory in the 20th century. Because the Big Bang Theory explicitly implied a “beginning,” it was strongly opposed by atheists on religious grounds. Though the Big Bang model is still being revised, its successes prove that the universe had a beginning, in agreement with the Bible.
Observational evidence for the validity of the Big Bang includes the expansion of the universe according to Hubble's law (as indicated by the redshifts of galaxies), discovery and measurement of the cosmic microwave background, the relative abundances of light elements such as hydrogen and helium, and the different appearance of distant (early) galaxies.
The Big Bang is a physical theory describing how the universe expanded from an initial state of high density and temperature. It is not a theory of the ultimate creation of reality. The Big Bang theory is based on Einstein’s theory of gravitation (General Relativity). In 1927, Catholic Priest and cosmologist Georges Lemaitre first presented the concept that an expanding universe, looking backwards in time, implied a single point of origin. There was significant resistance to the idea that the universe had a beginning because of the religious implications. Today, based on the evidence, most cosmologists accept the idea that the universe had a beginning. Of course, opinions vary widely on the initial cause. While we don’t know what happened in the first moments of the universe, all that we do know clearly points to an actual beginning.