Via Poliglut come two separate theories about why the WTC Towers collapsed so quickly.
In this corner we have chemistry professor Art Robinson. Robinson told World Net Daily that he believes the towers came down quickly because of New York’s 1971 ban on asbestos.
When the towers were originally designed, the columns were to be coated in a foam spray made from asbestos. Before the towers were completed, however, New York banned asbestos and the upper floors used an alternative insulation. Robinson says that Herbert Levine, who invented the asbetos foam spray that was to be used, said that, “If a fire breaks out above the 64th floor, that building will fall down.”
I’m extremely skeptical of this particular theory. Robinson makes much of Levine’s comment without even bothering to note that it is incredibly self-serving. Also this particular explanation is too reminiscent of the myth that the Space Shuttle disaster was the result of an asbestos ban (asbestos should not have been banned, but lets not try to blame every disaster on the irrational fear of asbestos).
In the other corner is G. Charles Clifton of the New Zealand Heavy Engineering Research Assocation who argues that it was the force exerted by the impact of the planes which ultimately doomed the towers. Clifton argues that the plane that hit the North Tower almost certainly took out the core supporting structures of at least three floors, causing the floors above them to sag. As the fire weakened the supporting columns, this effect would have become more exaggerated until the floors collapsed on top of each other pancake-style.
Clifton’s hypothesis also would explain why the South tower collapsed so much more quickly than did the North tower. Based on the videotape of the collision, Clifton notes that the plane that hit the South tower probably took out all of the core supports for at least 4 and probably 6 floors, as well as severely weakening the southeast corner of the building.
In both cases, Clifton argues that any resulting fire was not, in and of itself, enough to bring down the towers. In fact, he notes that the available evidence is inconsistent with a raging 700 degree fire that has been frequently hypothesized as the cause of the collapse (Clifton argues that if that scenario occurred, the towers wouldn’t have lasted nearly as long as they did).