Magnetism

In physics, magnetism is one of the phenomena by which materials exert an attractive or repulsive force on other materials. Some well known materials that exhibit easily detectable magnetic properties are iron, some steels, and the mineral lodestone; however, all materials are influenced to one degree or another by the presence of a magnetic field, although in most cases the influence is too small to detect without special equipment.

Magnetic monopoles

Contrary to normal experience, some theoretical physics models predict the existence of magnetic monopoles. Paul Dirac observed in 1931 that, because electricity and magnetism show a certain symmetry, just as quantum theory predicts that individual positive or negative electric charges can be observed without the opposing charge, isolated South or North magnetic poles should be observable. In practice, however, although charged particles like protons and electrons can be easily isolated as individual electrical charges, magnetic south and north poles do not appear in isolation. Using quantum theory Dirac showed that if magnetic monopoles exist, then one could explain why the observed elementary particles carry charges that are multiples of the charge of the electron.

Related Topics:
Magnetic monopoles - Paul Dirac - Electricity - Symmetry - Quantum theory - Positive - Elementary particles

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In modern elementary particle theory, the quantization of charge is realized in a spontaneous breakdown of a non-abelian gauge symmetry. It should be noted that the monopoles predicted in certain grand unified theories are different from the one originally thought of by Dirac. These monopoles, unlike that of elementary particles are solitons, namely localised energy packets. These monopoles, if they exist at all, contradict cosmological observations. A solution to this monopole problem in cosmology gave rise to the currently interesting idea of inflation.

Related Topics:
Abelian - Grand unified theories - Solitons - Cosmology - Inflation

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