When a wave function is time-reversed, it means that the behavior of a physical system described by the wave function is reversed in time. In plain English, it suggests that if you were to observe the system's evolution backward in time, you would see a reversal of the processes and events that occurred.
In classical physics, time-reversal symmetry implies that the laws of physics remain the same if time runs backward. However, in quantum mechanics, time reversal is a bit more subtle. The time-reversed wave function is obtained by reversing the direction of time in the mathematical equation that describes the system's behavior. This reversal can lead to interesting phenomena and insights.
For example, consider a simple scenario where a particle is moving along a certain path. If you time-reverse this situation, it would imply that the particle retraces its path backward. Any interactions or forces acting on the particle would also be reversed. Essentially, it is as if you are playing a movie of the system's behavior in reverse.
Time-reversal symmetry is a fundamental concept in physics, and it has implications in various fields, including quantum mechanics, thermodynamics, and particle physics. By studying the behavior of systems under time reversal, scientists can gain insights into the underlying symmetries and fundamental laws of nature.