Something to wonder about…(although this is not rigorous enough to be considered a proof)
The result of the Second Law of Thermodynamics is that systems tend to “run down”, “wear out”, “decompose”, and so on. Consider a ball rolling on a level floor. As it rolls, friction with the floor stirs up motion in the molecules of the ball and the floor (i.e., the ball and floor get slightly warmer – just as when you rub your hands together the friction makes them warmer).
This is a universal phenomenon. It is why physicists regard “perpetual motion machines” as impossible. And here is the relevance to the question of whether the universe had a beginning.
If universe did not have a beginning, then it has been around for an infinite time. In a sense, the universe is then itself a “perpetual motion machine”, a system that never “runs down” or “wears out”
Source: Spitzer, Robert PhD New Proofs for the Existence of God: Contributions from contemporary Physics and Philosophy 2010 Eerdmans Publishing