Shards of glass and dust from the World Trade Centre towers sit on Professor Steven Jones's desk at Brigham Young University in Utah. Evidence, he says, of the biggest cover-up in history - one too evil for most to believe, but one he has staked his academic career on exposing. Jones, a physics professor, is not alone. He is a member of 9/11 Scholars for Truth, a recently formed group of around 75 US professors determined to prove 9/11 was a hoax. In essays and journals, they are using their association with prominent universities to give a scholarly stamp to conspiracy theories long believed in parts of Europe and the Arab world, and gaining ground among Americans. It is impossible, says Jones, for the towers to have collapsed from the collision of two aeroplanes, as jet fuel doesn't burn at temperatures hot enough to melt steel beams. The horizontal puffs of smoke - squibs - emitted during the collapse of the towers are indicative of controlled implosions on lower floors. The scholars have collected eyewitness accounts of flashes and loud explosions immediately before the fall. What's more, the nearby World Trade Centre 7 also collapsed later that afternoon. The building had not been hit by a plane, only damaged by fire.

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