  The rest mass of the neutron is exactly equal to the rest mass of a proton
plus that of an electron plus the mass equivalent of the kinetic energy of
those two particles after they have electrostatically accelerated from very far
apart toward each other to a separation distance of one proton diameter. That
fact is either a remarkable coincidence or evidence that the neutron is a
combination of a proton and an electron. The calculation of this sheds new
light on the nature and significance of the Lamb Shift.
