We're used to magnets coming in two side-by-side flavors; north is always paired with south. If you take a magnet and chop it in half, you don't get an isolated north or south pole. Instead, you get two mini-magnets, each sporting its own pair of poles.
There's no superfundamental reason that single, lonesome north or south poles, called magnetic monopoles, should be forbidden in our universe. It just appears to be so. In the 1800s, scientist James Clerk Maxwell was putting the pieces together of our modern theory of electromagnetism, thus uniting magnetism, electricity and light under a single roof. When he looked around, though, he failed to see any monopoles, and wrote that into the equations: no monopoles, not here. [8 Baffling Astronomy Mysteries]
But Maxwell's electromagnetism is a classical theory and has been subject to enhancements and upgrades of the quantum variety in the past hundred years, and those upgrades allow for some pretty interesting creatures to roam our cosmos — among them, magnetic monopoles.
To hunt for monopoles, we have to go back to (nearly) the beginning: the earliest moments of the Big Bang itself. In those hot, crazy, frenetic days, the physics of the cosmos were radically different from what they are today. Indeed, the density and temperature of the entire universe was so high that some, if not all, of the fundamental forces of nature were melded together into a unified whole.
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