Entropy is one of the most fascinating concepts introduced in physics in the last two centuries. Keeping track of its value enables one to discriminate past events from future ones or, in other words, to keep an eye on the so-called “arrow of time”. This unique feature comes at the cost of the notorious difficulty to grasp what entropy is all about or what it actually measures.
In the meantime, entropy has been given the sulphurous interpretation of ‘disorder’ and seems to be accountable for any observable disorder around us. In this lecture, we will try to put on the suit of the devil’s advocate and investigate whether entropy can really be identified to our common idea of disorder. To this end, we will progressively lift the veil of mystery surrounding entropy as we explore various proposals that have been made about its fundamental nature and decide whether the idea that entropy measures disorder is tenable upon close inspection.