## Monday, December 07, 2009

### The Large Hadron Collider Pop-up book

Those worried about falling education standards, diminishing attention spans, and the debauched culture of modern liberal capitalist democracies, can rest easy in their beds tonight. Two physics books published this year eschew the modern habit of teaching science with the aid of visual gimmicks, and revert to old school methods, gripping the attention of the reader with the clarity of the prose and the innate fascination of the subject matter.

First up is Voyage to the Heart of Matter, which sounds like some dreadful confessional book by Joan Bakewell, but is otherwise known as the Large Hadron Collider Pop-up book.

Actually, this does look like a clever and original piece of work from 'paper engineer' Anton Radevsky. However, whether it is "Perfect for: teenagers who have studied the LHC at school or been lucky enough to visit CERN," is debatable.

Consider the following question: Why does the Large Hadron Collider accelerate two counter-rotating beams around a circle before colliding them into each other? Why not simply accelerate one beam, and smash it into a target which is at rest in the laboratory frame of reference? If the single beam is accelerated to twice the energy of each beam in the double-collider, then surely the energy of the collision will be the same?

If students of physics cannot answer this question, then they haven't grasped the most fundamental and important concept about particle accelerators. The answer to the question above depends upon the fact that the energy for creating new particles comes from the energy of the colliding particles in the centre of mass reference frame.

If one particle is at rest, and another particle is accelerated towards it, then the centre of mass of the joint system moves in the laboratory reference frame. (If the two particles have the same mass, the centre of mass will be the point equidistant between the moving particle and the target particle). Some of the energy of the accelerated particle goes into moving the centre of mass of the joint system, and it is only the remaining energy in the centre of mass reference frame which is available for creating reaction products. In this case, one needs to quadruple the energy of the accelerated particle to double the energy in the centre of mass reference frame.

However, in the case of two counter-rotating particles, the centre of mass remains fixed in the laboratory reference frame, so the laboratory reference frame coincides with the centre of mass reference frame, and the energy in the centre of mass reference frame is simply twice the energy of each particle.

A pop-up book clearly isn't going to communicate this type of crucial understanding, and that's obviously not the intention. It would be nice, however, if this type of book could ultimately inspire some students to develop a more sophisticated understanding in later years.

Next up is The Manga Guide to Physics, in which doe-eyed female teenagers learn about physics via the medium of tennis:

Megumi is an all-star athlete, but she's a failure when it comes to physics class. And she can't concentrate on her tennis matches when she's worried about the questions she missed on the big test! Luckily for her, she befriends Ryota, a patient physics geek who uses real-world examples to help her understand classical mechanics-and improve her tennis game in the process!

Perfect, then, for uncles as well as teenagers.