Time is one of the most mysterious aspects of our universe. At first glance, it seems simple: seconds, minutes, and hours pass, and we move from the past to the future. But when scientists try to define time, things become far more complex. Time is not just a measure of change; it is deeply connected to the structure of reality itself.

From a scientific perspective, time is often considered a dimension, similar to the three dimensions of space. Together, space and time form what is called space-time, which is the framework in which the universe exists. Unlike space, however, time seems to have a direction—it flows from past to future. This one-way movement is often called the arrow of time.

Why does time only move forward? One explanation comes from the concept of entropy. Entropy is a measure of disorder in a system, and according to the second law of thermodynamics, the total entropy of the universe always increases. This increase gives time a direction: the past is more ordered, and the future is more disordered. That is why we remember the past but not the future, and why causes precede effects.

Even though some theories in physics, like those of Albert Einstein, suggest that time could theoretically flow in different ways under extreme conditions, our everyday experience is dominated by this forward progression. It is not just a human perception—it is a fundamental feature of the universe.

In short, time is both a measure of change and a dimension that moves inexorably forward. Its one-way flow is linked to the natural increase of entropy, giving structure and order to the events of our lives. Understanding time helps us grasp the deeper workings of the cosmos, even if its full nature remains one of science’s greatest mysteries.