Daily Archives: September 4, 2009

One is the Loneliest Number

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Magnetic Monopoles Detected In A Real Magnet For The First Time

Magnetic monopoles are hypothetical particles proposed by physicists that carry a single magnetic pole, either a magnetic north pole or south pole. In the material world this is quite exceptional because magnetic particles are usually observed as dipoles, north and south combined. However there are several theories that predict the existence of monopoles. Among others, in 1931 the physicist Paul Dirac was led by his calculations to the conclusion that magnetic monopoles can exist at the end of tubes – called Dirac strings – that carry magnetic field. Until now they have remained undetected.

I’m guessing (from the Dirac string reference) that these aren’t the monopoles of standard electrodynamics, forbidden by Maxwell’s equations, but another weird result from condensed matter physics, to go along with fractional charge and spin-charge separation. This subtlety is probably going to be lost on the scientific fringe, though.

Update: Yeah, as I suspected. Via Starts With a Bang, the abstract says these are “emergent quasiparticles resembling monopoles.”

Doing it Right

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Illuminating physics for students by David Griffiths

Physics teachers are fortunate (I am among friends, so I can speak frankly): ours is a subject the relevance and importance of which are beyond question, and which is intrinsically fascinating to anyone whose mind has not been corrupted by bad teaching or poisoned by dogma and superstition. I have never felt the need to “sell” physics, and efforts to do so under the banner “physics is fun” seem to me demeaning. Lay out our wares attractively in the marketplace of ideas and eager buyers will flock to us.

What we have on offer is nothing less than an explanation of how matter behaves on the most fundamental level. It is a story that is magnificent (by good fortune or divine benevolence), coherent (at least that is the goal), plausible (though far from obvious) and true (that is the most remarkable thing about it). It is imperfect and unfinished (of course), but always improving. It is, moreover, amazingly powerful and extraordinarily useful. Our job is to tell this story – even, if we are lucky, to add a sentence or a paragraph to it. And why not tell it with style and grace?

Griffiths came down to Corvallis and gave a talk when I was in grad school. It was pretty good — I felt like I almost understood Berry’s phase when he was done. (OSU had its own David Griffiths; fortunately they did not annihilate upon meeting)

I found a particular resonance with this comment

I have known people who are in some sense too smart to be clear; they cannot remember what it was like not to understand something, because, I suppose, they never had this experience. They may be outstanding physicists, but they do not belong in the classroom.

When I was teaching, and later when merely explaining, I’ve tried to understand the misconceptions people have, and the barrier that the misconceptions create. It’s not enough to tell someone that their answer is wrong — they need to understand why it’s wrong, too. Remembering what it was like to not understand something is really useful.