September 29, 2023
CERN
Today was all about particle physics and our visit to CERN, the largest lab of its kind in the world. We took tram 18 from the downtown train/tram station all the way to its endpoint in Meyrin, the village on the outskirts of Geneva that hosts CERN.
The train station was about 100m from our hotel, can't be any easier! The tram 18 comes every 10 minutes or so. Modern, quiet, electric.
Inside the main exhibit building we read lots of wall signs - this is one of my favourites. The whole dark energy/matter thing was not even discussed back when I was at U of Toronto. Now we realize it comprises 96% of the mass in the universe - inferred because we cannot see it, cannot measure it. A mystery for the next generation.
The equation below is the current state of the art in describing matter/energy iteractions. Its a bit unwieldy because we still can't account for how gravity fits into the other forces in a single model. This conundrum was pursued unsolved by Einstein until his death. It remains unsolved.
The current accelerator is 27 km around - with two streams of particles going in opposite directions going about 0.999997 c, almost the speed of light.
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The ATLAS detector is 93m below us, and is one of the four main detector complexes on that big circle. I was wondering how they stop the interference of the muon stream from the sun's rays hitting the atmosphere (and cascading down through us), but they add a detector on TOP of ATLAS to detect those muons, then toss away any interactions that are generated for those few nanoseconds. Amazing technology.
Although the beams are not currently in operation (another nearly constant upgrade ongoing), historical record of the number of events is kept up in this counter. They generate something like 50 petabytes of data every day, and beam this to computers around the world for computation because that is just too much for one computer complex to handle.
Tomorrow its back on the bikes as we start our big turn towards the Med, and will end up tomorrow at Seyssel. It is still quite warm (high of 27 today) so we will try to get out a lot earlier tomorrow.
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