One of the first viral hits of the still-young internet, it encouraged millions to question what they were told. He had hoped the film would prompt a sober reassessment of the attacks. One hoax after another has emerged, each more bizarre than the last: birtherism. People can also very quickly find like-minded others, join groups, and share their opinions.
Conspiracy theories about the attack and its aftermath also gave early exposure to some of the same people pushing hoaxes and unfounded claims about COVID, vaccines and the election, including Alex Jones, the Trump-supporting publisher of Infowars, who has accused the United States of plotting the attacks and has said the Sandy Hook shooting was a hoax. Repeated surveys show a small percentage of Americans continue to harbor doubts about the official explanation of the attacks. Shocking, sudden events often spawn conspiracy theories as people collectively grapple with understanding them, says Mark Fenster, a University of Florida law school professor who has studied the history of conspiracy theories in America.
That runs into the Pentagon? Before the internet, conspiracy theorists relied on books, pamphlets and the occasional late night television show to espouse their beliefs. But according to an official report, the crashed planes considerably damaged support columns of both the towers and dislodged fire-proofing. Additionally, the fires reached up to 1,C in some areas, causing the steel beams to warp and the eventual collapse of the buildings. This building - containing offices of the CIA, the Department of Defense, and the Office of Emergency Management - collapsed hours after the Twin Towers without being hit by a plane or directly targeted.
But in , a three-year investigation by the National Institute of Standards and Technology concluded it had collapsed because of intense and uncontrolled fires - lasting for nearly seven hours - started by debris from the fall of the nearby North Tower.
But in , the Plasco tower in the Iranian capital, Tehran, became the second. The fact the collapse of 7 World Trade Center was announced in a live report by BBC News correspondent Jane Stanley - while it was still visibly standing behind her - has been cited by conspiracy theorists as evidence major media organisations were part of the inside-job plot. The Reuters news agency had mistakenly reported the collapse of the building, which was also picked up by CNN, just before the live report.
Some online conspiracy theories suggest US missiles were fired at the Pentagon, as part of a government plot, and the hole left in the building was too small to have been caused by a passenger plane.
But a member of the American Society of Civil Engineers told Popular Mechanics magazine the size and shape of the hole was due to one wing of the Boeing hitting the ground and the other being severed on impact with the building. Meanwhile, United Airlines Flight 93 crashed near Shanksville, Pennsylvania, after passengers tried to take control of the plane from the hijackers.
Online theories claim it was shot down by a white business jet flying into a nearby airport. But aviation officials had requested the jet inspect the area, which it did, reporting back evidence of a big hole in the ground with smoke coming out of it. When a few columns become damaged, the load they carry is transferred to other columns. These theories have developed from video footage showing the towers rapidly collapsing downwards some time after impact, similar to a controlled demolition.
But it is possible for them to have collapsed this way without explosives. It was fire that caused this. And the fire is believed to have come from the burning of remaining aircraft fuel. According to the FEMA report, fire within the buildings caused thermal expansion of the floors in a horizontal and outwards direction, pushing against the rigid steel columns — which deflected to an extent but resisted further movement. With the columns resisting movement, there was nowhere else for the concrete floors to expand to.
This led to an increased buildup of stress in the sagging floors, until the floor framing and connections gave in. The collapsing floors then fell on more floors below, leading to a progressive collapse. It is understood the South Tower collapsed sooner because it suffered more damage from the initial aircraft impact, which also dislodged more fireproofing material.
While there are different theories regarding how the progressive collapse of Building 7 was initiated, there is consensus among investigators fire was the primary cause of failure.
Both official reports made a range of fire safety recommendations for other high-rise buildings, including to improve evacuation and emergency response.
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