Friction is at play wherever surfaces meet, and it always begins with atoms. Atomic theories of the phenomenon usually focus on interatomic bonds, shared vibrations, and other surface-to-surface interactions as friction's ultimate source.
Now, two Texas-based physicists have modeled surface slippage–friction's retreat–as bands of atoms in the top surface momentarily leaping up from the underlying surface. Millions of such ripples propagate simultaneously along the interface when, for instance, a book slides on a table, they say.
Scientists have long known that friction on the scale of books and tables obeys simple laws. As French physicists Guillaume Amontons and Charles-Augustin de Coulomb established