Government apologists have argued that WTC 7 took 13 or more seconds to collapse, thus disproving the “virtual free fall” argument. However, this argument entirely misses the point.
Because the videos show that the penthouse collapsed long before the main building. In fact, everyone admits that there was a delay of several seconds between the collapse of the penthouse and the collapse of the rest of the building.
“An object at rest tends to stay at rest“. So once the movement stopped, it should have stayed stopped.
Therefore, the collapse of the main portion of building 7 - several seconds after the collapse of the penthouse stopped - should be treated as a discrete and new event (see discussion below).
Since the main building collapsed in approximately 7 seconds - the same time as a controlled demolition takes - that is strong evidence that WTC 7 was in fact demolished.
The important comparison is the collapse time for the main portion of a building. In videos of controlled demolitions, demolition charges are often visible long before the building starts to collapse, but these should not be included in the collapse time. If there are things going on inside the building after the charges go off but before the main building visibly starts collapsing, then that should not be included in the timing calculations.
In other words, government apologists will argue that alot was going on inside WTC 7 between the end of the collapse of the penthouse and the beginning of the collapse of the main building. They have provided no evidence for that argument. Indeed, if there had been significant movement inside the building after the collapse of the penthouse, this should have resulted in some movement or deformation of the building visible from outside.
More importantly, alot might also be going on inside other buildings between the start of demolition charges and the start of the visible collapse of the main building. There is simply no way to know (there are usually not cameras inside buildings being demolished, and there were no cameras inside WTC7 to capture what was happening; so this cannot objectively be measured).
The comparison should be in the time that the main buildings take to collapse. This is an objective measurement (unlike guessing about what is going on inside of a building when no movement is observable from outside), and readily observable from video.
Note: For any previous instances of controlled demolition when a penthouse, antenna or other roof structure was demolished before the main building, then - for the sake of consistency - that must be excluded from the collapse time when comparisons are made to WTC 7.
Update: Mechanical engineer Tony Szamboti agrees with this analysis, and adds:
“The WTC 7 East penthouse had columns on its perimeter and none in its interior. On three sides these columns mounted near the edge of the roof of WTC 7. It is unlikely that a collapse of any core columns of the main building could have pulled them completely down without the roof beams breaking completely loose from the exterior columns and moving down completely also.
It is unlikely that the roof beams were severed from the exterior columns, which is what would be necessary for a core collapse to cause the penthouse to collapse.”