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But what if single north and south poles exist, just like positive and negative electric charges? These hypothetical beasts, known as "magnetic monopoles," are an important prediction in several theories.

Like an electron, a magnetic monopole would be a fundamental particle. Nobody has seen one yet, but many—maybe even most—physicists would say monopoles probably exist.

"The electric and magnetic forces are exactly the same force," says Wendy Taylor of Canada's York University. "Everything would be totally symmetric if there existed a magnetic monopole. There is a strong motivation by the beauty of the symmetry to

If you chop a magnet in half, you end up with two smaller magnets. Both the original and the new magnets have “north” and “south” poles.

But what if single north and south poles exist, just like positive and negative electric charges? These hypothetical beasts, known as “magnetic monopoles,” are an important prediction in several theories.

But what if single north and south poles exist, just like positive and negative electric charges? These hypothetical beasts, known as "magnetic monopoles," are an important prediction in several theories.

Like an electron, a magnetic monopole would be a fundamental particle. Nobody has seen one yet, but many—maybe even most—physicists would say monopoles probably exist.

"The electric and magnetic forces are exactly the same force," says Wendy Taylor of Canada's York University. "Everything would be totally symmetric if there existed a magnetic monopole. There is a strong motivation by the beauty of the symmetry to

But what if single north and south poles exist, just like positive and negative electric charges? These hypothetical beasts, known as "magnetic monopoles," are an important prediction in several theories.

Like an electron, a magnetic monopole would be a fundamental particle. Nobody has seen one yet, but many—maybe even most—physicists would say monopoles probably exist.

"The electric and magnetic forces are exactly the same force," says Wendy Taylor of Canada's York University. "Everything would be totally symmetric if there existed a magnetic monopole. There is a strong motivation by the beauty of the symmetry to

But what if single north and south poles exist, just like positive and negative electric charges? These hypothetical beasts, known as "magnetic monopoles," are an important prediction in several theories.

Like an electron, a magnetic monopole would be a fundamental particle. Nobody has seen one yet, but many—maybe even most—physicists would say monopoles probably exist.

"The electric and magnetic forces are exactly the same force," says Wendy Taylor of Canada's York University. "Everything would be totally symmetric if there existed a magnetic monopole. There is a strong motivation by the beauty of the symmetry to

Dirac to the future

Combining the work of many others, nineteenth-century physicist James Clerk Maxwell showed that electricity and magnetism were two aspects of a single thing: the electromagnetic interaction. 

But in Maxwell’s equations, the electric and magnetic forces weren’t quite the same. The electrical force had individual positive and negative charges. The magnetic force didn’t. Without single poles—monopoles—Maxwell’s theory looked asymmetrical, which bugged him. Maxwell thought and wrote a lot about the problem of the missing magnetic charge, but he left it out of the final version of his equations.

Quantum pioneer Paul Dirac picked up the monopole mantle in the early 20th century. By Dirac’s time, physicists had discovered electrons and determined they were indivisible particles, carrying a fundamental unit of electric charge. 

Dirac calculated the behavior of an electron in the magnetic field of a monopole. He used the rules of quantum physics, which say an electron or any particle also behaves like a wave. For an electron sitting near another particle—including a monopole—those rules say the electron’s wave must go through one or more full cycles wrapping around the other particle. In other words, the wave must have at least one crest and one trough: no half crests or quarter-troughs.

Interestingly, the logic runs the other way too. Dirac’s result says if a single type of monopole exists, even if that type is very rare, it explains a very important property of matter: why electrically charged particles carry multiples of the fundamental electric charge. (Quarks carry a fraction—one-third or two-thirds—of the fundamental charge, but they always combine to make whole-number multiples of the same charge.) And if more than one type of monopole exists, it must carry a whole-number multiple of the fundamental magnetic charge.

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