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Fri January 31, 2014
Scientists Come Close To Finding True Magnetic Monopole
Originally published on Mon June 30, 2014 8:55 am
DAVID GREENE, HOST:
Scientists may have filled in a gap in one the fundamental theories of physics. We've always been told that magnets have two poles, north and south. But theory suggests there should be something called a magnetic monopole, a magnet that has either a north pole or a south pole but not both of them. So far no one has found this elusive magnetic monopole.
As part of his project, Joe's Big Idea, NPR's Joe Palca brings us the story of scientists at Amherst College in Massachusetts. They have created a synthetic magnetic monopole. Not the real thing, but close.
JOE PALCA, BYLINE: The search for the true magnetic monopole has been remarkably unsuccessful. David Hall is a physicist at Amherst College. He says certainly the straightforward searches haven't worked. For example, let's say you have a magnet in the shape of a needle.
DAVID HALL: It has a north pole and a south pole. And if it's a compass needle, the north pole points to the north pole of the planet, and the south pole points towards the south pole of the planet. Hence they get their names.
PALCA: So logic might suggest that if you chop the needle in half, there'd be just one pole in each piece. But no.
HALL: Once again you have a north pole and a south pole. These things appear to come in pairs all the time.
PALCA: Hall says you can keep chopping the remainder in smaller and smaller pieces all the way down to a single atom.
HALL: There's still a north pole and a south pole associated with this atom.
PALCA: In a single atom.
HALL: In a single atom.
PALCA: Now, there's a reason this is puzzling and that's because of something called the electromagnetic theory. That theory shows how electricity and magnetism are inextricably linked. Electricity has positive charge and negative charge just like magnetism has a north pole and south pole. But if you look at single atoms, they're made up of two distinct entities - protons that hold the positive charge and electrons that hold the negative charge.
So why, when you get down to the atomic level, why can't you find separate entities for magnetism?
HALL: Where are the north poles, where are the individual isolated north and south poles? You would think just by comparison to the electric charges, say, of the electron and the proton, that you ought to be able to do that.
PALCA: The theory suggests magnetic monopoles might be there; they even ought to be there. So physicists have kept looking.
HALL: And that may tell us more about humans than anything else, but it would be really nice if we could fill in that part of the theory with north and south individual isolated magnetic monopoles.
PALCA: Hall says he didn't have a brilliant idea about how to find a naturally-occurring magnetic monopole, but he read a theoretical paper by colleagues in Finland that suggested you could create a synthetic magnet monopole in the lab, so he thought, let's try that. What they did is extremely technical in nature.
Too technical for radio, you might say, but here goes: It involves cooling a collection of rubidium atoms down to a fraction of a degree above absolute zero, and then manipulating the resulting Bose-Einstein condensate in a way that allows the creation of a synthetic magnetic field into which the researchers introduce their synthetic magnetic monopole. Clear?
Well, if you really need more than that, I suggest you look up the paper in the current issue of the journal Nature. The point is, according to David Hall, they got their synthetic magnetic monopole to exhibit the main features that theory predicts for the real one - an experimental tour de force.
HALL: The insights that one might get from our experiment might tell us how that thing might behave, but it won't necessarily tell us where we're going to find it. It tells us to keep looking though.
PALCA: And if human nature is anything to go by, I'm guessing physicists will do just that. Joe Palca, NPR News. Transcript provided by NPR, Copyright NPR.