nHolds atom
together, also molecules.
nBoth
repulsive & attractive, due to existence of positive & negative charges.
n+ and
– charges must be almost exactly equal in number, to better than one part in 1040.
nYet protons
(+) and electrons (-) drastically different in mass, and froze out at quite different times in the early
universe.
nIf not for
this equality, e-m would dominate gravity, so no galaxies, no stars, no planets.
nE-m is
tuned to one part in 1040.