Are there any credible conspiracy theories?
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In the final report, NIST says this.
The approach taken by NIST is summarized in Section 3.6 of the final summary report, NCSTAR 1A (released Nov. 20, 2008; available at http://wtc.nist.gov/NCSTAR1/PDF/NCSTAR%201A.pdf) and detailed in Section 12.5.3 of NIST NCSTAR 1-9 (available at http://wtc.nist.gov/NCSTAR1/PDF/NCSTAR%201-9%20Vol%202.pdf).
The analyses of the video (both the estimation of the instant the roofline began to descend and the calculated velocity and acceleration of a point on the roofline) revealed three distinct stages characterizing the 5.4 seconds of collapse:
- Stage 1 (0 to 1.75 seconds): acceleration less than that of gravity (i.e., slower than free fall).
- Stage 2 (1.75 to 4.0 seconds): gravitational acceleration (free fall)
- Stage 3 (4.0 to 5.4 seconds): decreased acceleration, again less than that of gravity
https://www.nist.gov/pao/questions-and-answers-about-nist-wtc-7-investigation
This analysis showed that the 40 percent longer descent time—compared to the 3.9 second free fall time—was due primarily to Stage 1, which corresponded to the buckling of the exterior columns in the lower stories of the north face. During Stage 2, the north face descended essentially in free fall, indicating negligible support from the structure below. This is consistent with the structural analysis model which showed the exterior columns buckling and losing their capacity to support the loads from the structure above. In Stage 3, the acceleration decreased as the upper portion of the north face encountered increased resistance from the collapsed structure and the debris pile below.
You see the second building on the roof?
Take a look at what happens when that structure fails comes down watch the gif.
Here, the steel column core holding up the second structure gave way and the building falls rapidly.
Probably unable to see the problem taken years for you guys to notice anything unusual.
See all those broken windows running up the west wall opposite where the Penthouse collapsed?
Do you notice the building at stage of collapse before they appear?
The problem is that the building was rapidly falling here when windows broke on the west side, but NIST claims part of the building still provides resistance, slowing the fall (stage 1).
The reality is when that second structure went the building started to freefall. Apparently, NIST picked some artificial start time to slow that fall so they could claim fire caused it. The NIST screenshot matches the broken windows on the west side
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