Globe Theatrics

Herbi Dreiner and his students have taken their award-winning particle physics show to Cern, where it went down a storm

I'm sitting in the back of the Globe at CERN, Geneva, while the last of our three performances is on: of course it's in French, oh la la.

These have been harrowing but also very rewarding days. The long drive, and rehearsal all day on Tuesday. Since we bring so much equipment on and off stage during the show every stage and locality are a new challenge. Through all this the students have put on three fantastic performances and all in a foreign language. It is something we will all remember for a while and hopefully the audience took something home as well.

The CERN organisers received us kindly and were very helpful with all the technical issues of getting the show going. They have also filmed the last two shows and hopefully we'll get some good clips out of that.

The show is split into four parts: Atoms & Nuclei, Elementary Particles, Forces & Symmetries, and Cosmology. In each section we explain the basic underlying concepts with many live experiments. Two MCs present the show (Rebecca and Jessica: absolutely great job. Thanks for accepting the French challenge) and the other students perform the experiments (experience, in French), run the cameras, as well as the sound and lighting. It is intended to be fun, but hopefully the audience learned something as well. (I have mainly learned French here!)

The heart of the show are the experiments; some examples: we demonstrate radioactivity with weak alpha, beta and gamma emitters, detected by a Geiger counter connected to a loudspeaker. One can show their difference by their absorptive properties. The alpha rays are effectively stopped by a 10 Swiss Franc bill (indeed, a hard currency). The beta rays are stopped by a thin piece of aluminium, whereas the gamma rays are not even stopped by several plates of lead.

We also show some more exotic particles, such as the muon. It was first discovered in 1937 but is produced in abundance everyday in today's LHC experiments. The muon has similar interactions to an electron, but is about 200 times heavier. However, it also only lives about two millionths of a second, decaying to an electron and two neutrinos. Muons are for example produced when energetic protons from outer space strike our atmosphere. Despite their short lifetime they reach the Earth's surface in great numbers since they fly close to the speed of light. Their apparent lifetime is also extended exactly because they fly so close to the speed of light. This is the theory of special relativity in action.

We have constructed a muon detector using a standard thermos, based on an idea from Mainz University. The thermos is filled with water. On the top opening of the thermos we have screwed a photomultiplier tube. This is a sensitive detector which converts weak light pulses into an electronic signal. When the very fast muons from the cosmic rays traverse the water in the thermos (they easily go through the thermos wall) they produce a distinctive bluish light, called Cerenkov radiation. The light reflects off the internal walls of the thermos to the photomultiplier tube. The resulting electronic signal is connected to a strobe light which records each muon with a flash, visible in the dark auditorium. This is accompanied by some cool electronic music.

We also demonstrate antimatter on stage. But my favorite is our home made accelerator which shoots a wooden projectile at a quark target. Quark is a German type of fresh cheese, it comes in six flavours, some of which taste pretty strange. This is a truly bang and splash type of experiment, which the kids always love. The collision is recorded by a detector and we have a culinary read-out of the data.

The two morning shows were attended by French and Swiss school kids. Yesterday's evening show was open for the general public and was packed. We were very honoured that Rolf Heuer, the director of CERN, and his wife showed up and both seemed to enjoy it a lot. If you think you might like it, you should invite us to Britain. We would love to come!


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