Monopoly

The rule applies in physics: A magnet always consists of a north and a south pole. Two opposite charges form a so-called dipole moment. Theoretically, a single pole (without the corresponding opposite pole) would be called a “magnetic monopoly”. In the imagination it looks like this:

  • There is a pole at the end of a bar magnet.
  • This pole is extremely far from its opposite pole at the other end.
  • Therefore, the poles have no effect on each other.

If there were monopoles as single particles, they would be carriers of a magnetic charge corresponding to the electrical charge. As a result, magnetic charges would form the sources and sinks of the magnetic field. There are various hypotheses in physics as to the existence of such phenomena. In nature, however, researchers have so far only been able to observe magnetic fields with closed field lines (i.e. without sources and sinks).

Possible evidence of magnetic monopoles

Some solids contain electronic structures (so-called quasiparticles) that resemble a mixture of exactly the same number of individual north and south poles. These are sometimes referred to as magnetic monopoles, but can actually only occur in pairs (and not as free particles). Nevertheless, scientists are constantly working on further researching quasiparticles and their magnetic properties. Such experiments have been the focus of spin ice solids since 2009. These are monopole-like quasiparticles in the form of electron spins, which have the following features:

  • You can move freely through the solid (comparable to gas molecules).
  • They only exist in pairs as the north and south poles.
  • At the local level, they behave like sources of magnetization; globally, the magnetic field remains source-free.

In addition to quasiparticles, there are other phenomena that researchers are considering as evidence of magnetic monopoles. British physicist Paul Dirac hypothesized that magnetic monopoles in the form of elementary particles could be the counterpart to electrons. There are two arguments for this:

  • The remarkable asymmetry between magnetism and electricity, which is shown for example in the Maxwell equations, would be eliminated.
  • It could be explained why electrical charges only occur "quantized" (ie in integer multiples of the elementary charge).

Despite intensive research, Dirac and his successors have so far not been able to prove these assumptions. The rule of thumb remains the same: magnets always appear as dipoles.


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