A young woman wearing blue jeans, a hard hat and a big smile stands against a blank wall to get her photo taken. It's one of those intriguing images that make you wonder what it's all about.
"When people ask, I'll explain that we were deep underground," says Sharon Toogood, physics teacher at St Andrew's Secondary in Glasgow.
"And behind that wall was the Large Hadron Collider."
The party of 12 senior pupils and two teachers are taking a break in a packed schedule to chat about the highlights of their trip to CERN, organised by Glasgow University-based Science Connects and particle physicist Aidan Robson.
"I've been walking around these three days, looking at things, listening to people and thinking, `I can't believe I'm here.'" says Daniel Hannaway, from Our Lady and St Patrick's High in Dumbarton.
"So many people and different cultures work here," says Christine Nicol, from Bannerman High. "Some of their countries don't have peace between them, but the physics brings them together. That is cool."
With its young researchers of all nationalities, strolling in shirts and shorts among grass, trees, bicycle sheds and clean white buildings, the European laboratory for particle physics, near Geneva, has the look and feel of a campus university. Down under, where the Large Hadron Collider (LHC) resides, it's like nowhere else on earth.
Colder, in places, than outer space, hotter, at times, than the centre of the sun, the LHC is a hollow ring, 27 kilometres around, that accelerates particles to phenomenal speeds, then smashes them together and studies the debris, using intricate instruments and some of the best scientists in the world.
This is the experiment that announced the discovery in July of a new particle that could be the long-sought Higgs boson.
"It will take a lot of work to confirm that," says Dr Robson. "Most physicists would be happy if it weren't, because that would be pointing us to new science."
Besides probing the structure of the universe, CERN is keen to communicate its methods and human face to the public - especially teachers and pupils.
"We have visitors from all over the world, up to half of whom are school groups," Mick Storr, CERN head of teacher programmes and public visits, had told the students on their first day.
"Schools and teachers are our target audience. Schools, because they are the future. Teachers, because they hold the future in their hands.
"We hope that bringing you here will inspire you to study science, and perhaps come back to work here one day. There are many opportunities at CERN for young scientists and students."
School visits to CERN were praised in the recent curriculum impact report on the sciences from Education Scotland (TESS, 21 September). They provide a wonderful educational opportunity, says development manager Rebecca Crawford. "We are funded by the government to be an educational dating agency. We connect teachers and pupils with individuals and organisations who want to communicate their passion for science."
Planning this trip meant bringing several of these together, she says. "There is CERN itself, which runs guided tours for groups and programmes for teachers. Then there is Glasgow University's experimental particle physics group, which has a substantial presence at CERN. Dr Aidan Robson belongs to that group and runs hugely popular masterclasses in particle physics, for pupils and teachers from all over Scotland."
Last year, for the first time 10 secondary pupils were sent to CERN, says Dr Crawford. "We got funding from the Ogden Trust and the Scottish Universities Environmental Research Centre. CERN provided meals and accommodation. So the pupils paid nothing. We invited physics teachers to ask fifth-year students to write a short essay on what they'd gain from coming to CERN, and chose those we thought would benefit most.
"We did the same again this year, and Aidan and I came too, looking for ideas to get more young people involved in future. I'm not sure how achievable it is. But wouldn't it be wonderful if we could deliver this programme to every fifth-year physics student in Scotland who wants to come?"
It is quite a programme, says Miss Toogood - and not for the faint- hearted: "I've accompanied pupils on many educational trips," she says. "This is the most intense and the hardest work for the kids. They're getting new stuff thrown at them all the time - and they're loving it."
Activities start gently on the first day, with a visit to the Universe of Particles exhibition, a blend of science artefacts and audio-visuals inside a pinewood globe with the scent of a sauna in the hot Swiss sun. "The universe is a puzzling place," says the narrator. "It is very big, quite old and rather empty."
The pace picks up with the introductory talk from Dr Storr, followed by a visit to Atlas, the largest of the locations around the LHC, where particle collisions are studied with sophisticated instruments.
"We are one of two big multi-purpose detectors on the Large Hadron Collider," explains Glasgow University PhD student Genevieve Steele, directing the students' attention to a roomful of computers, attended by alert researchers.
"We examine everything, but our main interest is the Higgs boson. Atlas is 100 metres under our feet and operating right now. It's like a huge onion with layers for detecting different particles and events."
Even over dinner the main fare is still physics, as the students are joined on the pine-treed patio of the onsite restaurant, looking east towards the Alps, by PhD students from the University of Glasgow who chat about their lives and work.
"I really enjoyed that," says Andrew Barnshaw from St Thomas Aquinas Secondary. "They weren't what I was expecting. I learned that you don't have to be isolated to do science."
"They are normal people, just like us but a bit older," says Sarah Francis from Greenwood Academy. "So that makes what they do seem more achievable for us."
Two visits on the following day, to different sites around the LHC, sandwich a session with Dr Storr, in which he shows how fish tanks can be made into cloud chambers, in which the students see - when the lights are turned off - the fleeting white tracks of particles produced by cosmic rays.
"I enjoyed that session," says Sean Jones from Springburn Academy. "It was hands-on and the cloud chamber our group built worked well. We saw lots of tracks."
A high point of the morning visit, guided by Hungarian physicists Zoltan Szillasi and Noemi Beni, comes when the students see where the particles come from - a small red bottle containing enough hydrogen to supply the LHC with the protons it smashes for 50 years.
Scientists at CERN are encouraged to take their turn in guiding visitors from their home country, but doing so in a foreign language is beyond the call of duty.
"Noemi and I are teachers as well as physicists," explains Dr Szillasi. "Once you've learned how good it is to transfer knowledge and see in their eyes that they understand, you don't want to stop."
At CERN, the sociology is almost as interesting as the physics. Science is a cooperative endeavour, but professional progress comes through beating competitors. That tension is most evident between the teams at the two largest detectors, Atlas and CMS. At one point, Dr Szillasi, who works at the latter, refers to Dr Robson laughingly as "the enemy". The announcement of a discovery, such as the possible Higgs, is made only if these two teams, using different methods, come to the same conclusion.
"So we must not discuss our work because that could damage the science," says Dr Robson. "But there are a few husband-and-wife teams on the different detectors."
Even between the two teams from the University of Glasgow - one at Atlas, the other at a smaller detector called LHCb - there is professional rivalry.
"What we do here is more subtle and beautiful physics than at the general- purpose detectors," Patrick Spradlin tells the students, as he shows them around the site that searches for small differences between matter and antimatter.
The first highlight of the final day is a review of current understanding of what the world is made of - the Standard Model of particle physics - and how it can be tested and extended at the LHC. Delivered by Tony Doyle, head of the experimental particle physics group at the University of Glasgow, it's a fascinating hour for the students, who pose deep questions at the end, revealing how much they have absorbed during their short stay.
"Does the Higgs not couple to the photon then, since that has no mass?" asks Scott Clarkson, from Calderglen Secondary.
"Great question," says Professor Doyle. "It doesn't, but our best evidence for the Higgs came through detecting two photons created from a virtual loop of fermions that came into existence because of Heisenberg's Uncertainty Principle."
The final visit of the students' trip is a journey down below the sunlit fields of maize to where the action happens. Here, among the giant cooling systems and constant hum of stacked racks of electronics, Miss Toogood gets her photograph and the students come as near as they safely can to the science they've been hearing about for the past three days.
"Being that close to the Large Hadron Collider is something I will remember forever," says Eastbank Academy's Jamie Bell.
Interested schools should contact firstname.lastname@example.org l www.scienceconnects.org.uk l CERN education: https:education.web.cern.cheducationWelcome.html l CERN Courier, with latest news on the Higgs: http:cerncourier.comcwslatestcern
- CERN employs 2,300 people and hosts 10,000 visiting scientists from 608 research institutions and 113 nationalities.
- At 26.7 metres in circumference, the Large Hadron Collider is the world's biggest particle accelerator.
- It accelerates protons to 99.9999991 per cent of the speed of light.
- The data recorded by each of the big experiments at LHC will fill 100,000 DVDs every year.
Full details of design and construction of LHC and detectors available at: www.symmetrymagazine.orgbreaking20080825free-online-full- documentation-for-the-large-hadron-collider.