Entropy tends to increase because we move towards more likely states: all the atoms distributed at random throughout the box. Tracing the universe back in time to its beginning, you follow a path to a more and more implausible, low-entropy state. The remaining mystery, then, is why the universe began in such an improbable state.

 Entropy tends to increase because we move towards more likely states: all the atoms distributed at random throughout the box. Tracing the universe back in time to its beginning, you follow a path to a more and more implausible, low-entropy state. The remaining mystery, then, is why the universe began in such an improbable state.