As you can tell by the length of this chapter, I find it hard to stop talking about this wonderful subject. Thermal Physics is like an old but vibrantly modern city with a long, fabulous and meticulously preserved history: around every corner there is a host of fascinating shops, theatres, galleries and restaurants offering the latest goodies from a cosmopolitan state of the art, intermixed with libraries and museums that tell stories of heroic acts and world-changing events. "Shop till you drop!" Still, I have to stop somewhere.
The foregoing has been a rather unusual introduction to Thermal Physics. I have completely left out THE LAWS OF THERMODYNAMICS - the traditional starting point for the subject - in favour of a strictly conceptual (though often painfully formal, I know) explanation of the meaning of entropy and temperature, in the conviction that these notions can be generalized to provide tools for quantitative analysis of random statistical processes in realms where no one ever dreamed of applying the paradigms of Physics. In my zeal to convey this conviction, I have also omitted any discussion of the profound practical applications of Thermodynamics, like ENGINES and REFRIGERATORS. Worst of all, I have not told any stories of the bizarre spontaneous behaviour of large numbers of similar atoms under different conditions of temperature and pressure - the so-called EQUATIONS OF STATE and PHASE DIAGRAMS of gases, liquids and solids, from FERMI GASES to SUPERFLUIDS and SUPERCONDUCTORS. Part of the reason for this is that you need a bit more introduction to the phenomenology of Physics - QUANTUM MECHANICS in particular - before you can fully appreciate (or even, in some cases, describe) much of the above-mentioned behaviour. All I can hope to have done in this HyperReference is to have unlocked the door (and perhaps opened it a crack) to a world of wonder and magic where analytical thinking and mathematics play the role of spells and incantations. I urge you to continue this adventure beyond the limits (and end) of this HyperReference!