What is a Magnetic Monopole?
A hypothetical elementary particle that is an isolated magnet with only one magnetic pole — a north pole without a south pole, or vice versa. First theorized by Paul Dirac in 1931.
fundamental conceptA curated encyclopedia of the impossible particle
A hypothetical elementary particle that is an isolated magnet with only one magnetic pole — a north pole without a south pole, or vice versa. First theorized by Paul Dirac in 1931.
fundamental conceptIf even a single monopole exists anywhere in the universe, all electric charges must be quantized. The condition: eg = nħc/2, elegantly explaining why charge comes in discrete units.
eg = nħc/2
Paul Dirac published "Quantised Singularities in the Electromagnetic Field" in the Proceedings of the Royal Society, introducing the monopole as a consequence of quantum mechanics.
historical milestoneOn February 14, 1982, Blas Cabrera's superconducting loop detector registered a single event consistent with a monopole passing through. The signal was never repeated.
unconfirmed detectionIn Grand Unified Theories, monopoles arise naturally as topological defects during symmetry breaking in the early universe. They would be supermassive — about 1016 GeV.
theoretical predictionStandard Big Bang cosmology predicts far more monopoles than observed. This "monopole problem" was a key motivation for Alan Guth's inflationary universe theory in 1981.
cosmic puzzleThe Monopole and Exotics Detector at the LHC uses nuclear track detectors and aluminum trapping bars to capture hypothetical highly-ionizing particles including monopoles.
active experimentMaxwell's equations possess a hidden symmetry: swap E and B fields, swap charges and monopoles. This duality is exact in vacuum and has profound implications for quantum field theory.
deep symmetryIn 2009, emergent magnetic monopoles were observed in spin ice crystals — not fundamental particles, but quasiparticle excitations that behave identically to Dirac monopoles within the material.
analog discovery