The Top September 11 Conspiracy Theories:
"Numerous unfounded conspiracy theories about the September 11 attacks continue to circulate, especially on the Internet. Some of the most prevalent myths are:
1) The World Trade Center (WTC) twin towers were destroyed by controlled demolitions.
This is how the collapses may have appeared to non-experts, but demolition experts point out many differences:
* Demolition professionals always blow the bottom floors of a structure first, but the WTC tower collapses began at the upper levels, where the planes hit the buildings.
* Non-experts claim that debris seen blowing out of windows was evidence of explosive charges, but experts identify this as air and light office contents (paper, pulverized concrete, etc.) being forced out of windows as floors collapsed on each other.
* Demolition firms had very sensitive seismographs operating at other sites in Manhattan on September 11. None recorded any explosions during the tower collapses.
* Clean-up crews found none of the telltale signs of controlled demolitions that would have existed if explosive charges had been used.
* Cutting away walls, insulation, plumbing, and electrical conduits to place numerous charges on the towers’ structural columns in advance would not have gone unnoticed.
* For more information, see ImplosionWorld’s article on the WTC collapses, the National Institute of Science and Technology's 'Answers to Frequently Asked Questions,' and Popular Mechanics, parts 4 and 5."
State Department webpage debunking and refuting 9-11 conspiracy theories.