A long-hypothesized particle, stuff of tantalizing detection attempts and thrilling sci-fi novels, may have finally been sighted.

A magnet has a north and a south pole. If you cut that magnet in two, you get two magnets, each with its own north and south poles. No matter how far you subdivide a magnetic material, this is what happens. Both north end and south end. Theory and indirect measurements support the existence of matter with just one pole: a monopole. Scientists have searched in all kinds of materials — in particle colliders, in moon dust, in cosmic radiation — to no avail.

But now, a pair of papers in Science and another pair available on demonstrate convincing evidence of a substance that has monopoles: spin ice crystals (such as Dy2Ti2O7, in case you want to get your hands on some). The crystals seem to have tiny north points and separate tiny south points — less than a nanometer apart, but still separate.

[Via Nature News]