Many assume the Bible says that the universe is only six thousand years old. Others believe that the universe has always existed. This question is a fundamental problem of cosmogony — which is the study of the origin of the universe.
Now consider this fact.
Perhaps the clearest established fact about the universe is that it is running down. The Second Law of Thermodynamics states that physical processes tend toward disorganization. To put it simply — it is easier to scramble the egg than to unscramble it! Energy — light, heat, matter, etc. — in the universe at large is being continually dissipated. The physical universe will ultimately "die" when all energy is uniformly distributed. And this is exactly what the Bible says (Heb. 1:10-12).
Now consider the situation: Since the universe is running down — but has not yet run completely down — we can only conclude that the universe has not always existed. This is scientific proof that there had to be a BEGINNING! And the Bible says that there was a beginning (Gen. 1:1). However, the Bible does NOT say the beginning was only six thousand years ago. The age of the universe is not revealed in Scripture. It therefore is either knowledge man might discover for himself — and therefore did not have to be revealed — or it is knowledge unavailable to man and incomprehensible even if it had been revealed.
By studying the "life spans" of stars, scientists have estimated their ages to be about a few billion years (1 billion = 1,000,000,000). The decay rates of radioactive elements are assumed to make it possible to estimate the age of the solar system in which we live. Radioactive elements occurring naturally on earth and those contained in meteorites both show a possible age of from one to several billion years. So all of the radioactive elements prove that time since the beginning is greater than 6000 years.
The galaxies at the limits of the observable universe are believed to be moving away from us at tremendous speeds. Calculations based on these speeds lead to the likely conclusion that these galaxies could not have begun moving away more than a few billion years ago. So here is another proof of a universe that cannot always have existed.
Now it is not merely a coincidence that the calculations of the ages of galaxies, stars, meteorites, and the earth itself all give ages much longer than 6000 years. Yet some, assuming the Bible says the universe is six thousand years old, reject these undeniable scientific measurements. On the other hand, others reject the Bible because this scientific evidence contradicts certain doctrines which are supposed to come from the Bible but which in fact do not. These contradictions arise out of a lack of understanding of either the Bible or science or, more often, both. As we have shown here, what the Bible actually says and what man has discovered are in harmony.