Physicsy

A bit of physicsy-math about group velocity, if anyone's bored and willing to help

It is now time for us to delve into the world of atoms. Things will get physicsy here for a few pages, but bear with me. We'll get back to comic books soon enough, ...

This is rather a physicsy example, but it is of some importance in chemical systems, for example a charged polyelectrolyte (polymer) is modelled like this.