Nor Cal Truth Jan 31, 2011
This video clip is another example of the sheer speed in which the structure of the buildings were demolished.
The roof section is maintaining the structure of itself until it disappears behind the smoke for a second: It then reappears just as the clip is ending. What reappears is the steel facade of WTC #2 without any of the connections to the roof, floors or trusses. All the concrete seems to be turning into dust, debris and cloud.
Without explosives or incendiary devices a building could not perform this kind of destruction on its own, there is simply not enough energy.