The Impossibility of Past Time Travel: A Scientific Explanation

In a recent online discussion, Professor Ivica Puljak, a renowned scientist, delved into the intriguing question of time travel, offering a scientific perspective on its feasibility. While acknowledging the theoretical possibility of journeying into the future under specific, extreme conditions, Professor Puljak unequivocally stated that traveling to the past remains practically impossible. Professor Puljak elaborated on this concept by explaining that all objects around us are composed of an immense number of particles, such as atoms and molecules. He used a thought experiment involving a box of air molecules to illustrate his point. If one were to divide a box of air into two sections, removing all molecules from one side to create a vacuum, and then remove the partition, the molecules would randomly redistribute themselves throughout the entire box. The probability of all molecules spontaneously returning to their original half, creating a vacuum in the other half again, is astronomically small, effectively impossible. Applying this principle to time travel, Professor Puljak explained that reversing time would require every atom and molecule in the universe to return to a precise past configuration. Given the random movement of these particles, the probability of such a spontaneous reversal is so infinitesimally small that it can be considered impossible. He humorously cited Stephen Hawking's "time traveler party" experiment, where no one from the future attended, as an anecdotal reinforcement of this scientific impossibility. Professor Puljak emphasized that while something might not be strictly "impossible" in a theoretical sense, its probability can be so low that it becomes "unbelievable" or practically impossible.