Exactly 200 years ago, a French engineer introduced an idea that would quantify the universe’s inexorable slide into decay. But entropy, as it’s currently understood, is less a fact about the world ...

If you start with a very specific state, for example a box full of balls that are sorted exactly by colour, then if you shake the box a little, a higher entropy mixed state will develop over time.

Irreversible changes in physical systems — such as the breaking of a glass on hitting the floor or the formation of a crystal from its melt — only occur because of an increase in entropy (Box 1). Yet ...

According to the second law of thermodynamics, the entropy of an isolated system tends to increase over time. Everything ...