At one point in my life, I spent several years trying to understand surfaces. It had come as a shock to me to learn that surfaces rule the world. It came as even more of a shock to discover how difficult it was to understand or even measure what is happening at a surface. That makes a light switch made from a single hydrogen molecule sitting on a surface very interesting for what it can tell us about surfaces.
Before we get to the good stuff, we need to take a trip down (my) memory lane. What makes surfaces so important? What makes them so hard to understand?
An inscrutable dictator
To begin with, we're not talking about surfaces like the one your kitchen table provides for your dinner plates. Instead, the surfaces we're talking about are the ones you'd see if you could zoom in on your kitchen table to the point where individual atoms were visible, and some of the molecules from the air in the room would be bouncing off or occasionally stopping to sit on the surface until vibrations knocked them back off.