Originally Posted by wphamilton

But it does bring up something interesting about the mechanism of friction: that it works on the molecular level. Interlocking shapes of the molecules themselves as they are pushed into each other, plus potentially the effects of electrical charges. Of course on the much larger scale there are also peaks and valleys in the material itself (and the surface) and that also is part of it, but the interesting thing is that you're actually getting molecular interactions. The harder you push them together, the closer those molecules are and that increases the friction!