Still another form of e.d.o. Quantum mechanics describes van der Waals forces via Casimir potentials, simple, non-relativistic equations which take their name from Hendrick B. G. Casimir. This equation is accurate over a wide range of scales, with corrections on the order of unity being found in most situations of interest. Polar-polar potentials thus tend to produce energies which are small compared to the total energy of a given system. This low-energy behavior suggests some resemblance to gravitation, which a sample calculation will make more evident.
Monoatomic hydrogen is just such a system.
Herein lies a surprise. Recall that Newton's constant has multiple definitions in dimensional analysis. It does, however, illustrate the utility of alternative conceptualization made feasible by the use of e.d.o.s and Casimir potentials. The value of this approach lies in its ability to reveal new phenomena and relationships between seemingly well-known processes. A similar treatment might have been performed on quark-gluon coupling, say, where longitudinal virtuals have been found to play an active role.