The second law of thermodynamics says, in simple terms, entropy always increases. This principle explains, for example, why you can't unscramble an egg.

Running in reverse They found that the change in entropy was negative over time intervals of a few tenths of a second, revealing nature running in reverse.

Entropy is surely one of the most intriguing and misunderstood concepts in all of physics. The entropy of the universe must always increase – so says the second law of thermodynamics.

Nonequilibrium Thermodynamics: The study of systems that are not in thermodynamic equilibrium, focusing on the flows of energy and matter and the production of entropy.

One thing to keep in mind through all this is that the concept of entropy was introduced by mathematician who was trying to express the second law of thermodynamics in an equation.

As physicists extend the 19th-century laws of thermodynamics to the quantum realm, they’re rewriting the relationships among energy, entropy and information.

Entropy production lies at the heart of non-equilibrium thermodynamics, a field that examines systems away from equilibrium where continuous energy flows and irreversible processes dominate.