WE HAVE moved a step closer to finding cosmic monopoles - magnetic poles without their opposite. Two experiments using strange stuff called spin ice have provided the best evidence yet that monopoles really are out there.
Nearly 80 years ago, physicist Paul Dirac said it must be possible for magnetic north and south poles to exist separately. But despite decades of searching, not one has been found. Last year, researchers demonstrated that certain states of the crystalline material spin ice would create monopoles that rove about the crystal (New Scientist, 9 May, p 28). They would be seen as disturbances moving through the spins of atoms within the crystal.
Now two separate groups claim to have spotted just that. Tom Fennell and his colleagues at the Laue-Langevin Institute in Grenoble, France, recorded the disturbances when they fired a beam of neutrons at a spin ice crystal to see ...
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