by Jeremy R. Hammond
February 15, 2011
The Foreign Policy Journal

According to the National Institute of Standards and Technology (NIST), videos of the collapse of the 47-story World Trade Center 7 on September 11, 2001 show the building succumbing to a fire-induced progressive collapse. Many independent researchers and scientists, however, including over 1,400 professional architects and engineers who have signed a petition calling for a new investigation, disagree, pointing to evidence that it was deliberately brought down in a controlled demolition.

Despite the dramatically different conclusions drawn, there does exist widespread agreement on both sides on a number of important questions. Proponents of both hypotheses agree that the damage to WTC 7 sustained from the impact of debris from the collapse of the north tower (WTC 1) was not an initiating or determinative factor in the collapse. Both sides also agree that the system of transfer trusses and girders in the building that allowed it to be constructed above the Consolidated Edison New York electric power substation played no role in the collapse, that hypothetical fuel oil fires from tanks stored in the building for emergency generators was not a causal factor, and that the office fires did not result in any significant loss of strength of the building’s load-bearing steel columns.

While NIST initially denied that the building achieved gravitational acceleration during its collapse in its draft report for public comment, it was forced to acknowledge that this was indeed the case in its final report after high school physics teacher David Chandler submitted his own analysis showing that the building collapsed at free-fall for approximately 2.5 seconds, and that there was a sudden onset of free-fall. According to NIST, the period of free-fall was 2.25 seconds.

Link to the rest of the article The Mysterious Collapse of World Trade Center 7: Case Far From Closed