““The innards of that proton are far more messy and inelegant than we might have expected. Although this composite object is experienced by the outside world as if it simply contains two up quarks and one down quark, that is only part of the story. Look closer and we find that the structure of this composite particle is a stew of gluons and virtual quark and anti-quark pairs-popping in and out of existence within the allowances of the uncertainty principle. Energy and time are borrowed and balanced; stuff appears and disappears before the universal bookkeepers can get angry.””
