Paul Dirac's 1931 prediction launched a quest that has spanned nearly a century. A single magnetic charge -- north without south -- would complete the symmetry of electromagnetism and explain the quantization of all electric charge in the universe.
Maxwell's equations contain a hidden message: if magnetic charges exist, electricity and magnetism become perfect mirrors of each other. The monopole is the missing piece that would make the theory whole.
Every grand unified theory predicts magnetic monopoles as relics of the Big Bang -- impossibly massive particles formed when the forces of nature first separated from their primordial unity.
On February 14, 1982, a single detector at Stanford recorded what appeared to be a monopole passing through a superconducting loop. The signal was perfect. It was never repeated.
In 2009, physicists found emergent monopoles in crystalline spin ices. These quasiparticles behave exactly as Dirac predicted, carrying magnetic charge through crystal lattices like electrons carry electric charge through wires.
IceCube, buried beneath a cubic kilometer of Antarctic ice, searches for monopoles arriving from deep space. MACRO, deep under the Italian Gran Sasso mountain, ran for years. The cosmos remains silent.
The predicted overproduction of monopoles in the early universe was one motivation for cosmic inflation -- a period of exponential expansion that diluted their density to near-zero. The monopole problem helped birth modern cosmology.
QUEST CONTINUES