# How does QED explain friction between two bodies?

I was reading Brian Cox's "The Quantum Universe" and at one point he was taking the analogy of the ball resting at the bottom of a valley to explain the finite potential well or "electron in a box" situation.

He said how kicking the ball uphill but not with enough energy causes the friction between the ball and the surface of the hill to slow its motion, and he went on to say how this friction can be explained through Quantum Electrodynamics (QED). I'm curious as to how QED explains friction in such a situation.

• I think that's just a throwaway comment - QED explains everything in your everyday experience except for gravity (since you really don't encounter the strong or weak forces much at all). Aug 20, 2018 at 22:00
• Friction is derived from electromagnetic interactions, which are explained by QED. You'd have to put a huge amount of effort to actually use first-principles QED for this, though. Aug 21, 2018 at 0:23
• It's analagous to using statistical mechanics to explain the interactions of many molecules. Technically you just need the more "fundamental" Newton's laws (or Maxwell's equations, etc. as well) to describe the motion of each particle, but this would be tedious if not computationally impossible. The same thing is true here. We use simplified friction models since they do a fairly good job. Trying to actually use QED to describe friction, while technically more fundamental, would be tedious if not computationally impossible. Aug 21, 2018 at 1:14