A jarful of antimatter has been stolen from Cern's Large Hadron Collider by a secretive brotherhood intent on blowing up the Vatican. The substance is so volatile that if it comes into contact with matter it will explode with phenomenal force.

But hold on a minute. The jar contains an eighth of a gram of the elusive antimatter - far more than Cern scientists could produce in a lifetime - and the small jar could never possess a vacuum perfect enough to prevent the volatile particles from exploding.

What is more, the sleuths on the gang's trail - a Harvard symbologist and a Cern physicist - look suspiciously like actors Tom Hanks and Ayelet Zurer.

Speaking at a special preview of the film adaptation of Dan Brown's thriller Angels and Demons, hosted by the Science and Technology Facilities Council, Cern physicists picked apart the myths and realities of the science depicted.

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David Wark, professor of physics at Imperial College London and a former member of the Cern Super Proton Synchrotron Committee, was generally positive about Hollywood's treatment of the atom-smashing experiment.

But he was quick to pick the film's producers up on the things they got wrong.

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"Half of our critics say our work has no practical value, the other half say we are about to blow up the world. I wish they would make up their minds," he said. "The truth is that there isn't enough antimatter to blow up a communion wafer, let alone the Vatican."

According to Professor Wark's calculations, the destruction of one eighth of a gram of antimatter would produce energy roughly equal to one third of the Hiroshima bomb's power. "So the film-makers got that bit right, but it would take billions of years to create that much."

Another gripe was that, even if it could be carried in a jar, imperfections in any realistic vacuum employed would result in the gradual annihilation of the antimatter, generating levels of radiation that would prove fatal to the person holding it within five seconds.

Despite these flaws, Tara Shears, a particle physicist at the University of Liverpool who works on anti-matter experiments at Cern, said that the film had got a lot right. "We might not wear white coats as the film suggests but it's great to see a glitzed-up version of what we do," she said.

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She argued that if the film inspired interest in science, its faults could be forgiven.

Professor Wark agreed, saying science fiction was almost always based more on fiction than science. "The science is wrong in most movies, but if you point out that you couldn't produce enough antimatter to blow your nose, the movie would be over in three minutes."

john.gill@tsleducation.com.