Modern Physics
The Search for Magnetic Monopoles
After studying both electricity and magnetism, a natural question to ask is why the two things are so different. Charge comes in nice little discrete packets (protons and electrons), and everything builds up nicely from there like a good Lego set. But magnets just...are. There's no way to separate the north and south poles of a magnet in order to get a north magnetic "charge" and a south magnetic "charge."
However, just because there's no way for scientists to do it doesn't necessarily mean nature can't. The jury's still out on magnetic monopoles, as they're called, but there's at least one general consensus: if they do exist, they're elusive little buggers—even the American Physical Society calls monopoles the "Yeti of the subatomic world."9 And, like actual, funded, we-wish-we-were-kidding-but-we're-not scientific expeditions to find the Yeti, no one's quite given up on magnetic monopoles just yet. Only time will tell if monopoles actually exist, or if they're just a Tibeten hermit in a white monkey suit.
The search for magnetic monopoles is—or, at least, at some point was—undertaken with Ahabian devotion by some scientists. It is accomplished via a variety of devices called particle detectors. One of the most common and basic versions of detector used is a superconducting quantum interference device, or SQUID.10 SQUIDs are made of a loop of wire kept at a temperature so cold it is superconductive—that is, it has a resistance of zero ohms. A small current is fed through the loop, which splits evenly through each branch, and then it's left alone. Sometimes for months.
The wires are so sensitive that any slight change to the magnetic field in the loop will change the current flow. If a magnetic monopole were to wander through the room and happen to float through the SQUID's loop, the current would change—alerting the scientists to the presence of a monopole.
This has happened exactly once.11
Nevertheless, the search goes on, just in case. When asked about the monopole hunt these days, a SQUID-building physicist will thrust out his peg leg, fling out both his arms and shout, "Aye, aye! and I'll chase him round Good Hope, and round the Horn, and round the Norway Maelstrom, and round perdition's flames before I give him up."