1. I can't find a source that says less than a few nanometers.
2. 300 picometers is roughly the diameter of a helium diatom. The head cannot possibly float through hydrodynamic means if an air molecule can barely even fit under it.
> The head cannot possibly float through hydrodynamic means if an air molecule can barely even fit under it.
It can. Since siblings liked airplane analogies, here is another one: Consider the head to be an airplane. It has somewhat wing-similar features which provide a lifting force, but the actual read/write head sits below those features (like, say, a landing gear is below wings).
You can at least fit several layers of iron atoms into that gap, assuming they're part of the crystal lattice. So the surface does not have to be perfectly smooth.
1. I can't find a source that says less than a few nanometers.
2. 300 picometers is roughly the diameter of a helium diatom. The head cannot possibly float through hydrodynamic means if an air molecule can barely even fit under it.