Brian Cox explains why time travels in one direction – BBC [video]

Time is not a thing, is a mnemonic for counting movement.

There is no time, just movement. How do you measure time? You watch how something moves. If everything in the universe stopped moving, time wouldn't pass. No movement, no time. Want to go back in time? Simple. Move every piece of matter and energy in the universe back to where it was. Since we can't do that, time feels like it only moves in one direction.

The bigger question in my mind has always been Newton's first law. Why does everything move forever? From the smallest quark to the largest black holes... Nothing ever stops. That's weird.