2 October 2015
The last two days have seen the realisation of a pilgrimage for my physics-teacher husband, Dave. We’ve been to CERN. Twice.
And it’s all thanks to the money he won in a teaching award given by his school last year. The award was for excellence in improving student achievement. It’s voted on by the students and then endorsed by the board and has a value of NZ$6000. It must be used to enhance the winner’s professional knowledge. Given that said husband has been on and on and ON for years about how cool it would be to visit the global home of particle physics, there really wasn’t any other option for how the money would be spent.
So we’re here (via Singapore, to avoid the 35-hour travel marathon required to get to Europe in one hit).
Visit number one occurred on 30 September.
We’re staying in central Geneva, in a privately owned apartment on Rue Jean Charles Amat. It’s tiny (49 square metres) but lovely, and very close to the central train station, Gare Cornavin. It’s not cheap (but nothing is in Geneva — EVERYTHING is about twice the price we would pay at home), but happily, it also comes with a free public transport card that allows us to travel within Geneva for free, anywhere, by any form of public transport. And so it was that we hopped on the number 18 tram to CERN and travelled the 20-odd minutes to probably the densest concentration of brain power and physics PhDs anywhere in the world.
Just past a field of nearly-ready-to-harvest sunflowers, the tram stopped and everyone disembarked: the brilliant scientists alongside the gormless tourists. We arrived about an hour before our booked tour and took the time to view the newly opened Microcosm exhibition. It’s very much a work in progress, but gives the physics geeks amongst us something to fizz over while waiting for the guided tour. When it’s fully installed, it looks like it will be quite impressive.
If you want to know more about the ATLAS experiment at CERN, have a look here.
Just after 11.00 our tour guide, Christiano, appeared. Young, strikingly handsome and personable (with a wonderful, hard-to-identify European accent), Christiano completed his PhD in particle physics about 18 months ago in London. He spent two of his three years of PhD study at CERN, and now works there on the ATLAS experiment. He’s looking for ‘long-lived’ particles that result from particle collisions. In other words, particles that survive long enough to travel 5 m at the speed of light before decaying to nothingness. Yes, apparently that is a long time for one of these particles to live. Nobody’s found any yet, but theory suggests they exist.
Our fellow English-language tour participants ranged in age from teenagers to retirees. (I couldn’t help wondering how many brilliant physics brains might be standing alongside me. I just kept my mouth shut to avoid confirming my extreme ignorance.)
We started with an introductory video then moved a short distance and into a building with the synchrocyclotron. (I’m just pleased that I a) remembered its name and b) spelled it right on the first attempt…)
This contraption was built in 1957 and was CERN’s first particle accelerator. It’s a wee baby, only 157cm (I think that’s what Christiano said) in radius. The whole ‘loop’ fits in one room. But it revolutionised particle physics, being kept in operation for 33 years in total.
Mothballed now, it forms part of the public tour, and serves as a screen for part of the AV show. Kinda cool (see below).
Somewhere along the line Christiano was explaining that CERN started off accelerating electrons but moved on to accelerating protons, and there are pluses and minuses to each approach. For particle collisions, the more energy the better. To increase the energy of particles, you speed them up. The heavier the fast-going particle, the more energy it has. So fast protons are better (in energy-carrying terms) than fast-going electrons because they are more massive. The downside is that they make ‘messy’ collisions: because there’s more ‘stuff’ in a proton, when they crash into other protons the by-products include a lot of sub-atomic ‘rubbish’ (Christiano’s word), which makes the process of filtering out interesting data from not-interesting data more complex.
Electrons, on the other hand, create a much ‘cleaner’ collision, so hunting for the scientifically interesting particles is easier. The downside is that you can’t get as much energy into an electron collision because they’re lightweights. So, to carry as much energy as a proton an electron has to be going faster. The downside of the higher speed scenario is cyclotronic radiation. Now, cyclotronic radiation is radiation that happens as a result of acceleration (don’t even think of asking me how/why), and it increases in a manner that is inversely proportional to the radius of the particle accelerator (the smaller the racetrack the greater the amount of radiation leaking off it). That has something to do with things turning a corner not being in equilibrium and always accelerating towards the centre of the turn. I think. So, the only way around this particular problem is to build a much bigger accelerator. The problem with this logical solution is that big accelerators tend to be prohibitively expensive. So CERN uses protons (and also, I believe, lead ions). Got it? Good, because that’s the best you’re going to get from an arts graduate who never did physics at all in high school!
From the synchrocyclotron we moved to the control room for the ATLAS experiment. Just outside the office there is a large mural of the ATLAS detector. (There are lots of these detector-themed decorative elements all over CERN, we learned later.) Also, sitting innocuously beside the building, several huge cylinders of liquid nitrogen with ice forming on the pipes. The LHC needs mind-boggling quantities of this stuff to keep things cool enough (remember that 1.9 degrees Kelvin?).
In the ATLAS offices there is a glass wall separating the workers from the onlookers–creating a fishbowl/zoo effect. The scientists are clearly used to being the subject of tourists’ curiosity: we got an enthusiastic and geeky ‘monkey in a cage’ wave from one of them.
So there we were, watching a short presentation about ATLAS while the real physics happened on the other side of the glass. Presumably the scientists were ready for it. (See the last item on the Daily Plan for Wednesday below.)
From here we made our way back to reception, and our tour was over.
Dave spent up large in the gift shop (and I walked away with a book on Particle Physics–one of Oxford University’s short introduction series; and a book all about the birth of the Internet, which happened at CERN). And then it was back on the number 18 tram home… to find, later that evening, a text inviting us back to CERN the next day!
A physics-teacher friend of Dave’s has a friend from Melbourne University (Sean Crosby) who is currently working at CERN, and Dave had been fervently hoping that Sean might be able to spend a small amount of time with us while we were in Geneva. So he was pretty excited to get the text for a 2pm rendezvous the next day.
Sean, a computer genius, is currently on a three-month secondment to CERN (which ends in a week and a bit, so our timing was excellent!) His mission is to improve the efficiency of the cloud computing system used by ATLAS and other experiments (which was 20% less efficient than using a physical-hardware-based approach). The amount of data processed by these experiments is up there in peta-byte territory; and the speed at which it has to be processed is down in the nanoseconds. Completely beyond my comprehension. Anyhow, Sean and his team of two or three others have improved the efficiency of that system by 15.5%. So, let’s just say he’s quite clever…
Sean was exceedingly generous with his time, giving us two and a half hours. We had a chat and a coffee in one of the staff cafeterias, and then ventured into CERN’s ‘inner sanctum’. The scientists’ shared office building is modelled on a detector (cylindrically shaped), and decorated appropriately.
And I can’t forget this, just hanging on the wall in one of the corridors in another building…
And then, on the walk back, a decided oddity.
Unbeknownst to me until the previous day, CERN has a religious statue — a dancing Shiva. (Apparently, it is the bane of the receptionists’ lives — with so many tourists asking either if they can see it or demanding to know why a religious item is in a science establishment.) According to Wikipedia, “Nataraja, The Lord (or King) of Dance), is a depiction of the Hindu God Shiva as the cosmic dancer who performs his divine dance to destroy a weary universe and make preparations for the god Brahma to start the process of creation.” So, while a Hindu religious symbol at an experimental physics mecca (yes, that is an intentional mixed metaphor) doesn’t seem to make any sense, perhaps it is a fitting choice of religious symbol. And, it was a gift after all.
Anyhow, it’s tucked away between two buildings. Here it is.
So that was our time at CERN.
Next was the United Nations.