I have to apologise for the delay - yesterday was a bit intense, as we were invited to a Korean dinner (the food was fantastic!). Last week was the final week for our summer school. We had our presentation on Thursday (about, of course, the Opera of Lyon ;) and the final exam on Friday, which was neither too easy nor too difficult. This weekend we're visiting Lyon during the Journées de la Patrimoine, and I'll be sure to write about that! Now, though, back to what you've apparently all been waiting for ...

Geneva day 2! 

... Just joking. This post is about CERN. At about 1pm, we went on a tour (everything is free there so you can spend your money on the shop - I got a really cool cup!), which we had to book 3 days before. Half of the 24 places go online 12 days at 8:30, and the other half 3 days before, so try and be early when you know you're going to Geneva! We got really cool visitor badges that you're allowed to keep as well. There are tours offered in English and French, and we went on an English one as it fit our timetable best. Originally my roommate had wanted to go on a French one, but after actually doing the tour we were quite glad to have not chosen the French one ... physics is difficult enough already. 

The tour itself was composed of two parts, one visiting an ongoing experiment (ATLAS, where they found the Higgs-Boson, see picture below) and an old particle accelerator, which is now safe for visiting. I'll start with that, as our subgroup went there first. The accelerator isn't actually a ring structure, back then they were "small" enough to be built in a rectangular form, enclosed by two giant magnets. The whole experiment was closed off by 5m-thick walls to keep the radiation from getting out. Before we went there, we watched a 20min-video on the history and ongoing research at CERN. What I found really cool was that our tour guide was an actual physicist working there! This way we could ask any kind of question and get a really informed answer. At the old accelerator, there was another video explaining the history of different particle accelerators at CERN and how their network expanded gradually. 

The latter part of the tour was to visit ATLAS, where we watched a 3D-movie about how ATLAS was built - this is one of the 4 particle detectors, the second main part of the CERN structures. Of course it would be quite useless to accelerate and crash all those protons without actually getting results! What I didn't know was that the particles are actually accelerated in two different "rings", and only brought together in those four experiments. After the video, we could see scientists monitoring the ATLAS screens, only closed off behind a glass wall. I, for my part, would feel a bit like a zoo animal, but maybe you get used to it. 

After the tour and many questions, we also visited the two permanent exhibitions, one in a wooden globe (originally for an EXPO) and the other one in the visitor center. Much of the information given there we had heard in the tour before, but since it was a lot of infos, I was glad to have a more detailed approach. Both exhibitions were very interactive, with short videos and a lot of touch screens to explore the CERN buildings. They need about 45min to get the particles to accelerate, and the collisions take place on a 23hour cycle, then they lose speed and new ones need to be accelerated again. On a side note, they also have an antimatter production facility! The accelerator itself is actually 100m underground to shield it from radiation (and to not pay any property tax / rent whatsoever), and nobody can enter. Next year they are apparently going to renovate / upgrade the accelerators, so this way one can go underground! 

We stayed there until 5pm, where it closed and I actually had to rush to the shop to buy that cup I mentioned before. Tired, but well informed, we made it back to town (CERN is about 20min away by tram). More to explore the second day ... and sorry for the long post!