1 – The collapses of the towers defied the entire history of engineering

Fires lasting up to eighteen hours have never caused skyscrapers to collapse before or since 9/11, and the twin towers themselves had already suffered several other fires, including a very serious three-hour fire which ‘burned like a blowtorch’ and gutted 65% of floor 11 of the north tower in 1975, with no structural damage. Yet on 9/11, the north tower, WTC 1, collapsed 1 hour and 42 minutes after fires began inside and WTC 2, the south tower, lasted just 56 minutes.

The twin towers were designed to withstand several Boeing 707 impacts, with calculations showing that “all the columns on one side of a tower could be cut, as well as the two corners and some of the columns on each adjacent side, and the building would still be strong enough to withstand a 100-mile-per-hour wind” (Glanz and Lipton, City in the Sky: The Rise and Fall of the World Trade Center, p133) and that “Live loads on these columns can be increased more than 2,000% before failure occurs” (p365). Indeed, the official report by NIST (National Institute of Standards and Technology) found that the impacts of the planes did not contribute to the collapse of the towers except by removing thermal insulation, and that when the planes hit them the towers swayed only around 24 inches – two-thirds of their maximum in high winds (NIST NCSTAR1-5A, appendix K).

The steel used to build the towers was rated to withstand 2000˚F (1093˚C) for several hours. Hydrocarbon fuels such as jet fuel burn at a maximum temperature of around 1500˚F (825˚C) under ideal conditions, but the dull orange flames and dark smoke seen on the day, with few emergent flames, signify fires which are starving of oxygen and burning inefficiently at much lower temperatures, and NIST reported that the jet fuel would have burned off in “at most a few minutes” (NIST NCSTAR – 1, p183) leaving the fires to burn the building contents, just like ordinary office fires. Furthermore, the fires in the WTC towers got less severe over time – WTC 2’s fires appeared to have burned out before collapse – and never involved entire floors at any point. But fires would have to be extremely severe and widespread to heat steel columns to the temperatures of the fire, considering steel’s terrific capacity to conduct heat; a hotspot at any one point would be dispersed throughout the steel member, and ‘wicked away’.

Finally, although the official assertion is that collapse was caused by sagging floors breaking their bonds with vertical supporting columns and falling one on top of the other, video footage of the north tower, which shows the mast atop the tower sinking 10ft before the outer walls of the building start to move, indicates that collapse began in the centre of the building, where its vertical super-structure was strongest of all and the fires would have been most starved of air. This is not explained by official accounts.

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