The missing 'recipe': Thermal conduction 'revealed' starting from the foundations
It's a bit like the difference between preparing a dish following a recipe detailing ingredients and procedure, or trying to do it just by looking at photos of the dish: in many cases good results can also be obtained with the second method but, clearly, knowing the recipe not only guarantees a successful outcome but also allows us to devise variants of the dish, using different and perhaps even tastier ingredients. This also happens in the world of physics, where in some cases the "recipe" is completely lacking and one has to make do with approximate methods ("photos of the dish"). This is, or rather was, the case with thermal conduction, a very common phenomenon in materials. Although well known and extensively studied, so far it has never been given a theoretical description taking into account both the behaviour of atoms - regulated by the laws of classical mechanics -...