solar French physicist Nicolas Carnot proposed the ‘second law’ of thermodynamics in around 1840.

The entropy of an isolated system not in equilibrium will tend to increase over time, approaching a maximum value at equilibrium.

In a simple manner, the second law states “energy systems have a tendency to increase their entropy rather than decrease it.”

A way of thinking about the second law for non-scientists is to consider entropy as a measure of disorder.

So, for example, a broken cup has less order (more entropy) than an intact one, and it is more difficult to repair a broken cup (reducing its entropy) than to break an intact one (increasing its entropy). Likewise, solid crystals, the most organized form of matter, have very low entropy values; and gasses, which are very disorganized, have high entropy values.