On 9/11/2001, the World Trade Center towers collapsed at near free-fall speed. In other words, the tops of the buildings crashed through the rest of the buildings in about one second more than they would have taken to crash through thin air. Even the 9/11 Commission acknowledged that this was the case.
As the towers fell, the concrete in the structures, along with all of the office contents (e.g., carpets, desks, ball point pens, computers) were pulverized into a fine powder, and this powder, along with steel beams from the structures, was powerfully ejected outward from the collapsing towers. These facts are also undisputed.
The official explanation that has been offered for the fast rate of fall is that the undamaged floors below the impact zones provided essentially no resistance as the great weight of the damaged floors pancaked down onto them. However, if the undamaged floors provided essentially no resistance in the fall (or if the floors weren't "pancaking", which is what the National Institute of Standards and Technology -- NIST -- now says) then what would be the source of the energy to pulverize concrete and building contents and to eject steel beams and other debris hundreds of feet outward?
Or, to put it the other way around, if the collisions of the floors released enough energy to pulverize concrete and other materials and contents into dust and to forcefully eject steel beams, wouldn't these collisions have slowed the collapses of the towers to speeds far slower than free-fall speed? Is the pulverization and powerful ejection of material (absent the use of explosives) evidence of very strong resistance from the undamaged floors, and isn't such resistanceincompatible with the near free-fall speed of the collapses that was observed? Some researchers have referred to this problem as the "resistance paradox".
One explanation for the pulverization and ejection of material is explosives used in a controlled demolition. This is compatible with the near free-fall speed of the collapses and also compatible with the other ten characteristics of the collapses that, according to many, were observed: sudden onset, completely vertical fall, total collapse, sliced steel, pulverization of concrete and other materials, dust clouds, horizontal ejections, observed series of demolitions circling the structure – “demolition rings”, sounds of explosions, molten steel.
A good review (10/07): http://www.youtube.com/watch?v=wDKa1Q1GwTQ
To watch an M.I.T.-trained engineer explain the collapses, see:http://video.google.com/videoplay?docid=1822764959599063248
Here is a letter from a physicist suggesting that the official explanation of the collapses is absurd:
http://www.rense.com/general73/phy.htm
http://www.rense.com/general73/phy.htm
A basic discussion of the physics involved:
http://www.911blimp.net/prf_FreeFallPhysics.shtml
http://www.911blimp.net/prf_FreeFallPhysics.shtml
For a detailed analysis of the collapses by a Physics Professor, see: "Why Indeed Did the WTC Buildings Completely Collapse?" Steven E. Jones, Ph.D, at http://www.physics911.net/stevenjones.htm
An analysis of the NIST report on the collapses: http://rense.com/general74/nist.htm
A review of the testimony of firefighters relating to explosions:
http://journalof911studies.com/articles/Article_5_118Witnesses_WorldTradeCenter.pdf
http://journalof911studies.com/articles/Article_5_118Witnesses_WorldTradeCenter.pdf
An analysis of the inadequate momentum transfer to collapse the building by pancaking
A critique of the previous paper, and a response to that critique
An analysis of the initial movements of WTC1 -- explainable only by controlled demolition
If you are assuming that the suggestion of government complicity in any aspect of 9/11 implies an impossibly large government conspiracy, consider these points.