Gage likes to brag about how many people he's suckered into signing his petition with that "logic" after showing a video of WTC 7 falling (with the sound off, of course). The invalid inference is obvious enough to most people, but a bigger problem is that the premise is just bullshit: WTC 7 does not really look like a CD, much less sound like one.
The NIST WTC 7 FEA modeled the major structural members and connections, but some simplifications needed to be made to get the number of elements down to 3 million. One simplification was to omit the curtain wall which formed the exterior shell of the building, because it did not contribute to the gravity load-bearing capacity. However, it was quite strong and rigid because it was designed to resist wind loads. The NIST model approximates what was happening to the interior columns and beams of the building, but without modeling that rigid curtain wall, there's no reason to expect the model to look like the videos of WTC 7 in which all we can see is the curtain wall.
Furthermore, the NIST hypothesis does indeed explain the 2.25 seconds of freefall: about 8 floors above the 7th floor suffered a horizontal progressive collapse, so the freefall simply implies that by that point the columns were providing zero resistance because they were broken at their splices. But the NIST hypothesis also explains the 1.25 seconds of less-than-freefall before that as being the time when the columns were providing resistance but were buckling, allowing the building shell to descend about 7 feet. The NIST hypothesis also explains the 7 seconds or so before that, from the time that the east penthouse fell, as the time during which the interior structure collapsed progressively.
Since silent explosives do not exist, there is no reason for a rational person to seriously consider the CD hypothesis, but in fact there isn't any CD hypothesis that actually explains what was happening before the 2.25 seconds of freefall.
At some point, perhaps even you will start to consider the possibility that Richard Gage has led the "truth movement" down a blind alley with the WTC 7 nonsense. If he ever gets that independent investigation and the best he can do is call "experts" like Dusterwald to say "I don't understand this," then they're going to get clobbered by actual experts who not only understand it pretty well but can explain it.
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