The attacks of September 11, Jones asserts, were an "inside job", puppeteered by the neoconservatives in the White House to justify the occupation of oil-rich Arab countries, inflate military spending and expand Israel.

"We don't believe that 19 hijackers and a few others in a cave in Afghanistan pulled this off acting alone," says Jones. "We challenge this official conspiracy theory and, by God, we're going to get to the bottom of this."

While this sinister spin strikes most American academics as absurd, 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 due to frustration with the Iraq war and opposition to President Bush's heavily hyped "war on terror".

Their iconoclastic positions have drawn wrath from rightwing radio shows and caused upheaval on campuses, triggering letters to newspapers, phone calls from parents and TV cameras in lecture halls.

In the Midwest, 61 legislators signed a petition calling for the dismissal of a University of Wisconsin assistant professor, Kevin Barrett, after he joined the 9/11 Scholars for Truth. Citing academic freedom, the university provost defended Barrett, albeit reluctantly.

A Scripps Howard/Ohio University poll taken during the summer indicates that Americans are increasingly suspicious of the government's explanation of the events of 9/11: 36% said it was "very likely" or "somewhat likely" that federal officials either participated in the attacks on the World Trade Centre and the Pentagon, or took no action to stop them, "because they wanted the United States to go to war in the Middle East".

For most of the world, the story of 9/11 begins at 8.45am on September 11 2001, when American Airlines flight 11 smashed into the North tower of the World Trade Centre. But, tumble down the rabbit hole with Jones, and the plotline begins a year earlier, in September 2000. A neoconservative group called Project for a New American Century, which included the defence secretary, Donald Rumsfeld, and the vice-president, Dick Cheney, brought out a report arguing for a global expansion of American military and economic supremacy, and for the US to transform itself into a "one-world superpower". The report warned that "the process of transformation, even if it brings revolutionary change, is likely to be a long one, absent some catastrophic and catalysing event - like a new Pearl Harbor".

Excuse for aggression

The group, in concert with about 20 others, orchestrated the attacks of 9/11 as an excuse for pre-emptive global aggression against Afghanistan, then Iraq and soon Iran, the academics say. And they insist that they have amassed a wealth of scientific data to prove it.

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.

The twin towers must, they say, have been brought down by explosives - hence the container of dust on Jones's desk, sent to him unsolicited by a woman living in lower Manhattan. He is using X-ray fluorescents to test it for explosive materials.

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. WTC 7 housed a clandestine CIA station, which the scholars believe was the command centre for the planning of 9/11.

"The planes were just a distraction," says Professor James Fetzer, 65, a recently retired philosopher of science at the University of Minnesota. "The evidence is so overwhelming, but most Americans don't have time to take a look at this."

But Jonathan Barnett, professor of fire protection engineering at the Worcester Polytechnic Institute in Massachusetts, calls such claims "bad science". Barnett was a member of the World Trade Centre Building Performance Study, one of the government groups that investigated the towers' collapse.

Reluctantly, he has familiarised himself with the scholars' claims - many of them have emailed him. Yes, it is unusual for a steel structure to collapse from fire, Barnett agrees. However, his group and others argue that the planes' impact weakened the structures and stripped off the fireproofing materials. That caused the top floors of both towers to collapse on to the floors below. "A big chunk of building falling down made the next floor fall down, and then they all came down like a deck of cards," Barnett says.

The collapse of WTC 7 was also unusual, he admits. However, firefighters do not usually let a fire rage unabated for seven hours as they did on the morning of September 11, because they had prioritised the rescue of victims. "The fact that you don't have evidence to support your theory doesn't mean that the other theory is true," Barnett says. "They just made it up out of the blue."

Since the attacks, the US government has issued three reports into the events of the day, all of which involved hundreds of professors, scientists and government officials. The 9/11 Commission, a bipartisan group, issued a 500-page, moment-by-moment investigation into the hijackers' movements, concluding that they were connected to Osama bin Laden. The National Institute of Standards and Technology, a government agency, filed 10,000 pages of reports examining the towers' collapse. And the Federal Emergency Management Agency weighed in, examining the response to the attacks.

"To plant bombs in three buildings with enough bomb materials and wiring? It's too huge a project and would require far too many people to keep it a secret afterwards," says Christopher Pyle, professor of constitutional law at Mt Holyoke College. "After every major crisis, like the assassinations of JFK or Martin Luther King, we've had conspiracy theorists who come up with plausible scenarios for gullible people. It's a waste of time."

But Barrett says the experts have been fooled by an "act of psychological conversion" not unlike the tactics CIA interrogators use on their victims. "People will disregard evidence if it causes their faith to be shattered," he says. "I think we were all shocked. And then, when the voice of authority told us what happened, we just believed it."

Misleading the public

History has revealed that governments have a tradition of misleading the public into going to war, says Barrett, and the next generation of Americans will realise the truth. "Europe and Canada are way ahead of us on this."

The 9/11 scholars go to great lengths to portray themselves as rational thinkers, who have been slowly won over by a careful, academic analysis of the facts of the day.

However, a study of the full extent of their claims is a journey into the increasingly absurd: Flight 93 did not crash in Pennsylvania but landed safely in Cleveland; desperate phone calls received by relatives on the ground from passengers were actually computer-generated voices from a laboratory in California. The Pentagon was not hit by American Airlines Flight 77, but by a smaller, remote-controlled A-3 Sky Warrior, which shot a missile into the building before crashing into it.

Many of the 9/11 scholars have a history of defending conspiracy theories, including that the CIA plotted both the Lockerbie bombing and the plane crash of John F Kennedy Jr and his wife, and that "global secret societies" control the world.

Professor Robert Goldberg, of the University of Utah, wrote a book on conspiracy theories, Enemies Within: the Culture of Conspiracy in Modern America. He recounts a history of religious and political leaders using conspiracy theories for personal and political gain. The common enemy is usually Jews, big government or corporations. The public laps it up, either because these theories are more exciting than the truth, or out of emotional need.

"What the conspiracy theorists do is present their case with facts and figures: they have dates, meeting places and always name names," he says. "The case is always presented in a prosecutorial way, or the way an adventure writer presents a novel. It's a breathless account. They are willing to say hearsay is a fact, and rumour is true, and accidents are never what they seem.

"One of the stories is that a missile hit the Pentagon, and all the data is there. But what is missing is: what actually happened to the plane and the people on it? Conspiracy theorists avoid discussion of those facts that don't fit."

Perhaps it is no coincidence that the public's willingness to believe conspiracy theories parallels their dissatisfaction with the Bush administration. In recent years, the American public has felt misled over false claims that there were weapons of mass destruction in Iraq, and that Saddam Hussein was connected to 9/11.

Many fear infringements on their civil liberties now the National Security Agency has gained access to phone billing records from telecommunications companies, the Bush administration has engaged in wiretapping without court warrants and there are thousands of cases of indefinite detentions of American and foreign citizens without trial. Those who criticise the Bush administration's "war on terror" are accused of being unpatriotic.

By taking their criticisms to such extremes, though, the scholars risk caricaturing the opposition. None the less, they are pushing on, and imploring Congress to reopen the investigation.

"We're academics and we're rational, and we really believe Congress or someone should investigate this," says David Gabbard, an East Carolina education professor and 9/11 scholar. "But there are a lot of crazies out there who purport that UFOs were involved. We don't want to be lumped in with those folks."