Electric charges come in two types, positive and negative. Magnetic poles also come in two types, North and South. In both cases, like charges/poles repel, and opposites attract. The big difference? Electric charges can exist in isolation; you can have just a positive or negative charge by itself. Whereas in a magnet, you always need both a North pole and a South pole; you can’t have a magnetic monopole.
Magnetic monopoles have always been a curiosity for physicists, and many of us think that they ought to exist. In the 1970s, there were searches going on for them, and the most famous one was led by a physicist named Blas Cabrera. He took a long wire and made eight loops out of it, designed to measure magnetic flux through it. If a monopole passed through it, he would get a signal of exactly eight magnetons. But if a standard dipole magnet passed through it, he’d get a signal of +8 followed immediately by one of -8, so he could tell these apart.
So he built this device and waited. Occasionally he’d get one or two magnetons, but the fact that it wasn’t eight was hardcore evidence that something funny was going on with just one or two loops. (Three or more was never seen.) In February of 1982, he didn’t come in on Valentine’s day. When he came back to the office, he surprisingly found that the computer and the device had recorded exactly eight magnetons on February 14th, 1982. Huge devices with larger surface areas and more loops were built, but despite extensive searching, another monopole was never seen. Stephen Weinberg even wrote Blas Cabrera a poem on February 14th, 1983:
Roses are red,
Violets are blue,
It’s time for monopole
And, as of today, no one has seen good evidence for a second magnetic monopole, leading us to believe that the first one was spurious.
And then I saw this headline over at ScienceDaily:
Damn. And I just tried defending science journalists to a clearly unhappy Sheril Kirshenbaum, and then someone goes and reports, “Magnetic Monopoles Detected…”
You can stop there. They haven’t been. In fact, if you go to the actual paper in science, they say so right in the abstract (bold emphasis is mine, as always):
While sources of magnetic fields–magnetic monopoles–have so far proven elusive as elementary particles, several scenarios have been proposed recently in condensed matter physics of emergent quasiparticles resembling monopoles.
What they did was create magnetic “strings”, or very long, thin magnets on a lattice, where North and South poles are separated by great distances. If you only look at one side of this string, you only see one pole. But the other pole is still there, and so this isn’t a monopole. If you tried to snap the string, you still wouldn’t isolate one magnetic charge; it would work just like this:
Now, this isn’t to belittle the research done here. The creation and isolation of these magnetic strings, and the separation of the poles over long distances is wonderful! As the researchers themselves say, “Above all, it signifies the first time fractionalisation in three dimensions is observed.” So instead of a network of magnetic strings like this:
They’ve managed to separate and isolate a single string! The technique was pretty amazing too, getting down to 0.6 Kelvin to do this experiment. But magnetic monopoles? Please! The science is sensational enough without the addition of outright lying.