Explosive Events in the Twin Towers
While the explosive nature of the events that destroyed the Twin Towers is evident in their gross features such as the mushrooming of the tops and the huge clouds of concrete dust produced in the air, there are many specific observations that point to the detonations of explosions within the towers.
Energetic Ejections of Dust and Objects
Explosive ejection of dust early in the collapse of the South Tower is clearly visible in the NBC video taken from far to the east, and in still frames from that video, portions of five of which are shown on the right. In addition to the large ejections of white dust from the left wall, the video shows a small high-speed ejection toward the back of the right wall, visible as a small white fleck in the first frame to the right.
Many of the photographs of the tower collapses show solid objects, such as sections of steel columns and aluminum cladding of the outer walls, being thrown ahead of the expanding dust cloud. This pattern is characteristic of explosive demolitions. According to Chapter 1 of FEMA's own report pieces of the steel columns and plates of the perimeter walls were thrown over 500 feet from the towers. The distribution pattern they diagram suggests that, with both towers, perimeter wall pieces were thrown an average of about 150 to 200 feet outward. This is corroborated by the shape of the vertical holes in WTC 6.
South Tower Demolition Wave
A three-second movie shows about 2.5 seconds of the South Tower collapse starting at about three seconds into the plunge of the tower's top. The short movie shows the roughly spherical debris cloud nearly double in size, even accounting for the perspective. The leading edge of the wave is about to reach the 44th-floor sky lobby when the camera operator turns to run. The movie (mpeg) was found on plaguepuppy's cafe with the following description.
Though the view of the building is brief, looking at it in slow motion reveals some peculiar features. At the very start of the clip we can see how perfectly even the collapse is, advancing with what looks for all the world like rows of explosions progressing in a perfectly straight line around the building, and advancing down in an extremely uniform way. As the demolition wave advances there is only dust and smoke where the top of the building used to be, and a great quantity of dust mixed with small pieces of structural steel is ejected out horizontally at high speed. To account for this very rapid ejection of debris without the use of high explosives, especially in the early stages of the collapse, seems quite impossible.
If you look closely as the wave travels down it seems to spare the corners, perhaps letting them lag behind to help keep the implosion aligned. The demolition wave is clearly advancing ahead of the actual collapse of the structure, and speeds up as it travels down. The delays between demolition charges would have to be very precisely controlled to create this effect, suggesting to me that each floor was wired to a separate detonator, with control of the sequencing most likely done remotely. This would also allow the collapse to be triggered from the point of impact of the plane to make it look more realistic. Such sequencing could easily be done from a laptop connected wirelessly to the towers, as long as each floor could be detonated separately.1