There is a great experiment that one can do either for real or in the mind. Imagine holding an ordinary bar magnet. Such magnets are easily obtainable and usually have a little “N” and a “S” marked on the North and South poles, respectively. Now imagine breaking this “two-poles” or “bi-polar” magnet in half. What will happen?
If you guessed that the two resulting half-sized magnets each would have their own north and south poles, then that would be correct. If you repeated the experiment, this would result in four small magnets also each with a north and south pole. And as you cut the magnets into still smaller pieces, this bi-polar behavior would continue. Why it is not possible to cut up a magnet in such a way as to get a “mono-pole” magnet, or one with no distinct north and south pole?
After all, in electricity there are currents, where electrons move along field lines from negative to positive direction analogous to the magnetic dipole field lines. And there are also electric charges, which are characterized by having only a single negative charge for an electron and positive charge for, say, a positron. Why is there no monopole equivalent for magnets?
Is it possible that we do not understand some very basic aspect of electricity and magnetism, or is it just that we simply have not yet found any magnetic monopoles out there in nature? If such an object does exist it will have to be small, and it will also have to have a very strong charge of 4700 times as strong as the repulsion experienced by two repelling electrons.
New experiments are now underway at the Large Hadron Collider (LHC) to find them, called the Monopole and Exotics Detector at the LHC (MoEDAL) to detect them. In time, perhaps we will know what may be missing from our standard model and will be able to explore new physics. What’s your vote?