A machine that probes the heart of matter and depths of time needs to be used with great care and precision. "When the Moon is overhead, the length of the tunnel expands by just one millimetre," says Bruce Dunlop, physics teacher at Stewart's Melville College in Edinburgh.
"But the scientists will take account of that small expansion in analysing their experiments, even though the whole tunnel is enormous - 27km in circumference."
One of a party of Scottish science teachers who returned at the end of February from a sponsored trip to CERN in Geneva - where scientists explore the particles and forces from which the world is constructed - Mr Dunlop will remember the visit for the rest of his life.
"The care, the intricacy and the scale of the Large Hadron Collider is mind-blowing," he says.
The most ambitious experiment at the European laboratory for particle physics, the Large Hadron Collider is designed to answer fundamental questions about the physical world. It opens for business in May. So the 16-teacher expedition from Scotland is one of the last that will be allowed to step into the tunnel, which will soon be bathed in lethal radiation.
By smashing high-energy particles together, the LHC will recreate, at very small scales, conditions that existed just billionths of a second after the hot, dense fireball in which the universe began. As-yet-undetected elementary particles should be discovered.
The Higgs boson, an elusive entity named after Edinburgh University physicist Peter Higgs, is one of the most eagerly anticipated.
"But I think the CERN scientists will be just as happy if they don't find the Higgs," says Mr Duncan.
"That will mean there is something wrong with their existing theory and they will have to develop new ones."
Besides the 17-mile-long, particle-smashing tunnel situated 100 metres below the French-Swiss border, the experiment has two other major components. These are the particle detectors and the Grid, a worldwide network of computers set up to analyse the rivers of data that will soon start flowing.
"The Atlas detector is as big as our school," says Mr Duncan. "It will have to capture more data in a day than the world's telephone network carries in a year."
But while the scale and ambition of the LHC in particular, and CERN in general, are impressive, they are not the most abiding memories of the trip, says Mr Duncan.
"We attended lectures by scientists each day. Rolf Landua who runs the anti-matter factory, was particularly inspiring.
"Teaching school science tends to be about following processes to pass exams. But Dr Landua was talking about people who had a problem-solving, open-minded approach. He was talking about the wonders and mysteries of the universe."
As an experienced teacher, Mr Duncan has learnt how to get people through exams, he says. "And I will still have to. But that's not the same as being a creative scientist. I'm going to try to share some of that enthusiasm and inspiration."
Perhaps the single most important aspect of what he saw at CERN is that it is a truly international, collaborative effort, says Mr Duncan. "Scientists from all over the world are in harmony there, searching for knowledge."
The teachers' trip was funded by the Institute of Physics and the Science and Technologies Facilities Council, www.iop.orgactivityeducationTeacher_SupportGrantspage_4712.html
More about CERN and the Large Hadron Collider, with lots of teaching and learning resources, at http:public.web.cern.chPublicWelcome.html and www.lhc.ac.ukfor-teachersteacher-s-resources.html
Extracts by Mae Thomson, Bearsden Academy.
"After installing ourselves in our rooms at CERN, some of us were given a short tour of the attractions:
The library. `Hi Jack,' says Mick Storr, CERN's educational officer and our host - then sotto voce to us, `That's Jack Steinberger, Nobel Prize winner'.
The office where Tim Berners-Lee invented the world wide web. Mick was working in the same office at the time. His contribution apparently was that, when Tim said, `Hey Mick, what do you think of the name world wide web?', Mick replied, `Yeah, it's OK'.
The main auditorium, where breakthroughs have been announced, and the famous have spoken."