9/11 Conspiracy Theories

9/11 conspiracy theories allege that the September 11 attacks in 2001 were either permitted to proceed even though known about in advance, or were a false flag operation orchestrated by an organization with elements inside the United States government.
In a 2008 poll of 17 countries, 15% of those surveyed believed the US government was responsible for the attacks, 7% believed Israel was and another 7% believed some other perpetrator, other than al Qaeda, was responsible. The poll found that respondents in the Middle East were more likely to name a perpetrator other than al Qaeda. The most prominent conspiracy theory is that the collapse of the World Trade Center and 7 World Trade Center were the result of a controlled demolition rather than structural weakening due to fire. Another prominent belief is that the Pentagon was hit by a missile launched by elements from inside the U.S. government or that a commercial airliner was allowed to do so via an effective standdown of the American military. Motives cited by conspiracy theorists include justifying the invasions of Afghanistan and Iraq, and geostrategic interests in the Mideast, including pipeline plans launched in the early 1990s by Unocal and other oil companies.
Published reports and articles by the U.S. National Institute of Standards and Technology (NIST), the magazine Popular Mechanics, and the mainstream media accept that the impacts of jet aircraft at high speeds in combination with subsequent fires, rather than controlled demolition, led to the collapse of the Twin Towers. Zdenek Bažant and Mathieu Verdure, writing in the Journal of Engineering Mechanics, propose that collapse can be triggered if the total internal energy loss during the crushing of one story exceeds the kinetic energy impacted to that story.
[Source: wikipedia.org]