[originally published in September 2009]
At 5:21 in the afternoon of 9/11, almost seven hours after the Twin Towers had come down, Building 7 of the World Trade Center also came down. The collapse of this building was from the beginning considered a mystery. 
The same should have been true, to be sure, of the collapse of the Twin Towers. But they had been hit by planes, which had ignited big fires in them, and many people assumed this combination of causes to be sufficient to explain why they came down.
But WTC 7 had not been hit by a plane, so it was apparently the first steel-framed high-rise building in the known universe to have collapsed because of fire alone. New York Times writer James Glanz quoted a structural engineer as saying: “[W]ithin the structural engineering community, [WTC 7] is considered to be much more important to understand [than the Twin Towers],” because engineers had no answer to the question, “why did 7 come down?” 
From a purely scientific perspective, of course, there would have been an obvious answer. Scientists, presupposing the regularity of nature, operate on the principle that like effects generally imply like causes. Scientists are, therefore, loathe to posit unprecedented causes for common phenomena. By 9/11, the collapse of steel-framed high-rises had become a rather common phenomenon, which most Americans had seen on television. And in every one of these cases, the building had been brought down by explosives in the process known as controlled demolition. From a scientific perspective, therefore, the obvious assumption would have been that WTC 7 came down because explosives had been used to remove its steel supports.
However, the public discussion of the destruction of the World Trade Center did not occur in a scientific context, but in a highly charged political context. America had just been attacked, it was almost universally believed, by foreign terrorists who had flown hijacked planes into the Twin Towers, and in response the Bush administration had launched a “war on terror.” The idea that even one of the buildings had been brought down by explosives would have implied that the attacks had not been a surprise, so this idea could not be entertained by many minds in private, let alone in public.
This meant that people had to believe, or at least pretend to believe, that Building 7 had been brought down by fire, even though, as Glanz wrote: “[E]xperts said no building like it, a modern, steel-reinforced high-rise, had ever collapsed because of an uncontrolled fire.”  And so, this building’s collapse had to be considered a mystery – insofar as it was considered at all.
But this was not much. Although WTC 7 was a 47-story building, which in most places would have been the tallest building in the city, if not the state, it was dwarfed by the 110-story Twin Towers. It was also dwarfed by them in the ensuing media coverage. And so, Glanz wrote, the collapse of Building 7 was “a mystery that . . . would probably have captured the attention of the city and the world,” if the Twin Towers had not also come down.  As it was, however, the mystery of Building 7’s collapse was seldom discussed.
For those few people who were paying attention, the mysteriousness of this collapse was not lessened by the first official report about it, which was issued by FEMA in 2002. This report put forward what it called its “best hypothesis” as to why the building collapsed, but then added that this hypothesis had “only a low probability of occurrence.” 
This FEMA report, in fact, increased the mystery, thanks to an appendix written by three professors at Worcester Polytechnic Institute. This appendix reported that a piece of steel from WTC 7 had melted so severely that it had gaping holes in it, making it look like a piece of Swiss cheese.  James Glanz, pointing out that the fires in the building could not have been hot enough to melt steel, referred to this discovery as “the deepest mystery uncovered in the investigation.”
The task of providing the definitive explanation of the collapse of WTC 7 was given to NIST, the National Institute of Standards and Technology. Although NIST had been expected to issue its report on this building along with its report on the Twin Towers, which came out in 2005, it did not. NIST then continued to delay this report until August of 2008, at which time it issued a Draft for Public Comment.
1. NIST’s Denial of Evidence for Explosives - READ MORE: http://www.globalres...wtc-seven/15201
Edited by macaense, 11 September 2015 - 07:49 PM.