Why does time only move forward? Or rather, if time is flowing, why does it only flow in one direction? What stops time from moving backwards? Well if time could move in both directions that would cause chaos in the universe, and, ironically, it is chaos itself that prevents that backwards flow of time from taking place.
The movement of time is the latest topic tackled by one of our absolute favorite YouTube science channels, MinutePhysics. It turns out that the reason for the one-way flow of time can be explained by the Second Law of Thermodynamics, which says that any isolated system will move towards entropy until it reaches equilibrium (a.k.a. its fully disordered/chaotic state). As it moves towards that state, time is moving forward, only ceasing to flow in any direction at all when full equilibrium is reached.
We can then apply that understanding to our own existence. Since we experience time right now we know we are not in equilibrium, so we must be in a lower state of entropy moving forward. That’s because the universe started in an even lower state, which we know as the Big Bang. The universe continues to move forward towards more chaos, and with it time only moves forward.
Of course, all of this means that someday time will stop flowing entirely, when the universe reaches full equilibrium. However, by then no one will be around to notice time isn’t moving at all anymore, since in that final state there will only be empty space in every direction. Total chaos will mean the universe will be totally quiet.
What other big questions about our universe would you like to see MinutePhysics tackle next? Take a minute of your time and let us know in the comments below.