Magnetic detection of magnetic monopoles

The idea of magnetic monopoles has a long history, but it wasn´t until Dirac´s demonstration that monopoles could explain charge quantization that the modern era began. Unfortunately, experiment did not oblige by finding any monopoles so for the next fifty years monopoles were only an interesting curiosity. When ´t Hooft and Polyakov demonstrated that monopoles are an inevitable consequence of gauge theories currently being used to unify the electroweak (photon-lepton) and nuclear (quark) interactions, interest was quickened. Then a solitary, uncorroborated candidate event was found last spring at Stanford which indicated that magnetic monopoles might exist. However, the monopole abundance implied by the Stanford event is in clear contradiction to bounds on their number from astronomical data. Chief among the arsenal of detection techniques have been those that are uniquely magnetic. Here we review the monopole idea with emphasis on its magnetic detection.