It’s *Physics World* time again, folks!

This month’s (July 2008) issue has a cover headline “On reflection: Symmetry and the Standard Model”, and a diagram of the 8-dimensional E8 group squashed flat like a beached jellyfish on the 2-dimensional page. The article itself (by Stephen Maxfield of Liverpool University) is as good a summary of the development the Standard Model as I’ve come across, and does serve to persuade me that those guys, by and large, really do know what they’re talking about. But what are they talking about? As in Wikipedia when they say such things as “Rotating a spin-1/2 particle by 360° does not bring it back to the same quantum state, but to the state with the opposite quantum phase; this is detectable, in principle, with interference experiments. To return the particle to its exact original state, one needs a 720° rotation!” How is one to enter such a world? Let us take the first step.

John Stillwell, in the preface to his book “Mathematics and its History”, tells us that one of the commonest complaints of undergraduate mathematician is that they never get a course in mathematics. They have courses in algebra, number theory, you-name-it, but important bits which connect these modules are left out.

But what about physics, where it seems one has Newtonian Mechanics until along-came-Einstein and next came Quantum Mechanics. Is there any cartilage around to join these dry bones? Yes, there is, if you look in the 19th Century. I have recently been reading “Icons and Symmetries” by Simon L. Altmann, Oxford University Press (1992), ISBN: 0198555997. Alas, this book is not only OUP, but OOP (out of print). Nevertheless, it is well worth getting hold of, and you can find a Product Description here.

The first chapter deals with one of those “moments in physics” which open a completely new perspective. Hans Christian Ørsted (Denmark, 1777–1851) had tried to show from 1812 that an electrical current could make a magnetic needle move. He thought of the current as a billiard cue that, in order to displace the compass needle, would have to be perpendicular to it. Early in 1820, during a lecture, he saw the needle turn when, astonishingly, the current was parallel to the needle. This was not only the beginning of modern electrical science, but the first time ever that a force was found not acting on the line of action of its vector, and moreover it broke the rules of symmetry as then understood. Such *tensorial* forces later became essential in the understanding of physics.

He has written a poem about this occasion:

Villanelle for Hans Christian Ørstedby Simon L. Altmann

The Dane saw the needle move,

the current and the compass parallel.

The world was amazed, was it a fluke?Not casual work, eight years it took,

eight hard years for the stubborn Dane.

The Dane saw the needle move.Until then, always running in a groove,

now at last the triumph of the great.

The world was amazed, was it a fluke?No one could begin to prove

how a force could act that insane.

The Dane saw the needle move.Newton would have thought it rude

to posit a force so new and strange.

The world was amazed, was it a fluke?Yet in this manner somewhat crude

a millennial question was then tamed.

The Dane saw the needle move,

the world was amazed, was it a fluke?

Some students might take “move” to mean a translation rather than rotation. However, one cannot substitute the word “turn”, since the rhyming rules for Villanelles are very strict indeed.

He is very keen on the use of poetry to inspire the teaching of physics, so if you have strong opinions on this his email is: simon.altmann AT bnc.ox.ac.uk

Next blog, *Deo volente*, we shall go Mathematical Tomb Raiding.

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