Magnetic field lines, as illustrated by a bar magnet: a magnetic dipole. There’s no such thing as a north or south magnetic pole — a monopole — by itself, though. Image credit: Newton Henry Black, Harvey N. Davis (1913) Practical Physics, The MacMillan Co., USA, p. 242, fig. 200.

Why doesn’t our Universe have magnetic monopoles?

We have electric charges and currents in electromagnetism, so why not magnetic ones, too?

“It is possible to commit no mistakes and still lose. That is not a weakness. That is life.” –Jean-Luc Picard

When you talk about the fundamental forces in the universe, there are only four different types: the gravitational force, the electromagnetic force and the strong and weak nuclear forces. What causes these forces to exist? In each case, there’s an underlying, fundamental property of matter that enables interactions to occur: a type of charge. For gravity, it’s mass; for electromagnetism, it’s electric charges; for the strong nuclear force, it’s color charges; and for the weak nuclear force, it’s weak hypercharge. But it didn’t have to be that way! There could have been not only electric charges at play in electromagnetism, but magnetic ones as well. For some reason, though, our universe doesn’t seem to have any, even though physics could completely allow it. Our universe is not symmetric.

Image credit: Murdoch University in Perth, Australia, via Jerri-Lee Matthews.

In gravitation, the force that any mass exerts on another is equal and opposite to the force exerted…