The magnetic monopole is one of the great absences in physics — a particle predicted by theory, demanded by mathematical elegance, yet never observed. Paul Dirac showed in 1931 that the existence of even a single magnetic monopole would explain one of the deepest mysteries of nature: why electric charge is quantized.
If monopoles exist, every fundamental charge in the universe — every electron, every quark — carries its particular value because somewhere, perhaps at the edge of the observable cosmos, a magnetic monopole anchors the quantization condition.
Grand unified theories predict that monopoles were produced copiously in the first moments after the Big Bang, when the unified force shattered into the separate forces we know today. Each symmetry-breaking phase transition could have spawned topological defects — knots in the fabric of the field — and monopoles are the most elegant of these defects.
They are heavy. Stupendously heavy. A single GUT monopole would mass 1016 GeV — a hundred trillion times the proton mass, packed into a volume smaller than a proton. A speck of matter carrying the magnetic charge of a universe.