Units So in the notes I often end up using different unit systems (usually those of whichever source I was reading, or whichever class I was in when I was taking the notes). In the Quantum Mechanics notes, for instance, you might notice that h-bar has suddenly vanished, or that in the Stat Mech notes, the Boltzman constant has disappeared. And that's because we're implicitly switching to a different unit system. There's way too many files to actually use a consistent set of units in all of them. Not to mention cluttery. So it's good to know how to convert from one system to another. That's what this file is for.