What Hannibal’s crossing cost

That thermodynamics has so very many applications is as fascinating as what it so often illuminates. Its tools and methods can be brought to bear on everything from celestial bodies and industrial machines to cellular biology and human endurance. The simple reason is that energy is the fundamental currency of the physical world: no physical process can occur without transferring or transforming it. Thus the laws of thermodynamics provide a near-universal framework to understand the limits and possibilities of any system in motion. In a study published in Proceedings of the National Academy of Sciences on July 6, researchers from Germany and the UK used the principles of thermodynamics to say which route the Carthaginian general Hannibal Barca might have taken through the Alps. Hannibal’s crossing, with an army of 46,000 men, 7,000 horses, and 37 North African elephants, during the Second Punic War is one of the great events of military history. However, the precise route he took has…