Thermodynamics of Time Travel
Many people like to imagine that it would be possible to go back in time. Maybe they want to change something that happened in the past. They don’t understand that forward motion in time as we perceive it is essentially a thermodynamic phenomenon and going backward in time is just an extremely improbable occurrence. Let me explain by considering two different scenarios. Scenario 1: Imagine a cylinder of compressed air in a sealed room that has had all of the air removed so it is a vacuum. A valve on the tank is opened and the gas flows out of the cylinder until the pressure in the tank matches the pressure in the room. The flow of gas represents the forward motion of time. The gas particles are moving randomly, bouncing around the room, off of surfaces and each other. Scenario 2: Next, imagine the opposite. You are sitting in a room with a compressed gas cylinder with an open valve on it. Suddenly all of the air in the room moves into the gas cylinder forming a vacuum in the room. In b