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 ...

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.

One of the enormous conceptual ideas that came along with Einstein's theory of relativity was the surprise that time itself, long considered fundamental and universal, is actually relative. Different ...

Imagine you’re standing in front of a closed door. Behind it is a teenager’s bedroom, and your task is to rate how messy it is on a scale of 1 to 10. But here’s the twist: you can’t open the door – ...