Science can be fun – really!
Why write this piece?
Early January 2011 the BBC science show Horizon presented a show led by the comedian Ben Miller who also it transpires studied for a PhD in Physics in Cambridge at the Cavendish! As he was so kind as to spend several minutes talking in front of yours truly (and zooming into my livery i.e. the phrase Reality Checkpoint carved into my paint) I was inspired to add my minor reflections on thermodynamics to his thoughts.
What is Thermodynamics
If you look at the wiki article you can summarise thermodynamics as the physics of heat and energy. An amazing aspect to me is how philosophical it all is and how it tells us fundamental things about reality (my favourite subject). It also speaks to the bridge between classical physics and the more modern understanding of things (in the sense of twentieth century).
We all work with the ideas of classical thermodynamics; we pump gas into a car tyre to increase the pressure, we blow up a balloon to increase its volume, we know that hot air rises as air expands when heated. Classical physics treats these outward properties of a system as being all encompassing link Pressure, Volume and Temperature in a holy Trinity and viewing matter as a continuous fluid entity.
Needless to say this is all false!
Here we need to understand the importance of scale; consider a room, it is a lot bigger than a molecule of gas. To help really understand that statement, consider that a typical room probably contains a vast number of molecules around 10 to the power of 27. This is a number so large then even written as one thousand trillion trillion it makes no sense. In perspective, there are only several 100 billion stars in the Milky Way, another incomprehensible number.
Consider one molecule it has a volume, but it doesn’t have a temperature or pressure! In fact all it has is speed (kinetic energy). The speed of each molecule is random as they ‘collide’ with walls and each other, but across such a vast number we get a perfect curve of energies and therefore behaviours that equate to pressure (as the molecules hit objects) and temperature (again from the energy transfer to cooler objects or from hotter objects!
Well, the part that always astounds me is that the simple model of gas as a continuous fluid or a room full of vast numbers of molecules all whizzing around produces the same equations!
This is why we simplify our description of a gas and talk about it in ways the standard mind can follow!