Physicists define time as the progression of events from the past to the present into the future. Basically, if a system is unchanging, it is timeless. Time can be considered to be the fourth dimension of reality, used to describe events in three-dimensional space. It is not something we can see, touch, or taste, but we can measure its passage. Physics equations work equally well whether time is moving forward into the future (positive time) or backward into the past (negative time). However, time in the natural world has one direction, called the arrow of time.
The question of why time is irreversible is one of the biggest unresolved questions in science. One explanation is that the natural world follows the laws of thermodynamics. The second law of thermodynamics states that within a closed system, the entropy of the system remains constant or increases. If the universe is considered to be a closed system, its entropy (degree of disorder) can never decrease. In other words, the universe cannot return to exactly the same state in which it was at an earlier point.
Time cannot move backward
The second law of thermodynamics is a fundamental law present since the Big Bang and one which seems to simply be an initial condition of the universe, continuing its course ever since that iconic explosion 13.8 billion years ago. But there are experiments that dispute the idea that entropy is the reason time flows forward. The idea of a universe in which all events exist simultaneously is both a grim and a comforting one: things and people which we’ve lost aren’t gone, merely a little out of our reach at the moment. But it also means we might not have as much say in the future as we hope. Of the many things we can do with time, it seems there is one which we haven’t yet managed to understand it…
This says that if at all time has to travel backwards then u must travel faster than speed of light which is impossible till date. That is the reason why speed of light is special.
