The UW 9/11 Research Group, which previously sponsored two presentations by truthers, has finally gotten around to hearing the other side.
Ron Craig, a professor at Ryerson University with extensive training and experience in explosives, gave a talk Friday night in the Arts Lecture Hall at the University of Waterloo. Here's a brief summary:
He started by asking, "How many people here believe the WTC buildings were brought down by explosives?" Sadly, about half the people in the audience of approximately 100 raised their hands.
He then showed clips of the WTC buildings collapsing, some eyewitness testimony, and excerpts of last year's appalling presentations by
A. K. Dewdney and
Graeme MacQueen. He then asked rhetorically, "After seeing all this, how could you not believe the towers were brought down by explosives?"
Briefly, his answer was "expectation bias": investigators reach a premature conclusion without examining all the relevant data.
9/11 "Truthers" start with a presupposition, then look for data to support it. By contrast, real fire investigators start with documents such as
NFPA 921, which outlines a scientific basis for investigating these incidents.
Craig pointed out that the WTC buildings used an innovative design for lightweight construction. They were the first super-high buildings to use this kind of construction, without heavy girders. The buildings weighed only 1/2 of what a conventional building would have weighed.
When demolition experts want to bring down a building, he said, they drill into columns and place the explosives. But no cement columns were used in the WTC. Furthermore, maintenance at the buildings reports that core beams above the 84th floor were inaccessible.
He then examined one claimed scenario for controlled demolition: in this scenario, explosives were placed on every floor. He then estimated how much explosive would be needed in this scenario, and came up with 1300 pounds of TNT-equivalent per floor, for a total of 143,000 pounds. Clearly this would be infeasible to set up without someone noticing.
Furthermore, such a large amount of explosive would have blown out windows in other buildings for blocks around. But this did not occur. In an explosive detonation, the typical inury is from flying glass, but there is no evidence that this occurred, nor evidence of other kinds of projectile injuries.
Explosives create heat of as much as 7000 degrees. Thermal injuries will be accompanied by primary blast injuries caused by pressure when the shockwave progesses through the body (e.g., middle ear injuries). "Blast lung" can occur at 50 to 150 psi. But not a single person in NY exhibited any symptoms of PBI.
Claims that thermite was used is undermined by the fact that no barium nitrate was found in the debris. He estimated that 61,000 pounds of thermite would have been needed. Again, it would have been impossible to set this up without someone noticing. Claims that sulfur was a signature of thermite/thermate are silly, because both the elevator shafts and stairwells were constructed with drywall, which is gypsum (calcium sulfate with 18% sulfur content).
Claims that molten steel was still flowing 21 days after the attacks are implausible. He showed one slide that supposedly depicted white-hot metal being observed by workers; it was actually just a worklight, as a video showed.
There is no good evidence that there were pools of molten steel. Many metals were at WTC, and low-temperature alloys could easily have formed. NFPA 921 says "if this occurs it is not an indication that accelerants were used or were present in the fire."
He then addressed the claim that "no other steel frame building has ever collapsed because of fire". He addressed other fires, such as
this one at Delft. During the fire there was a
partial collapse with "squibs" visible just as in the WTC.
He compared the WTC fire to other fires, such as the one in Madrid and
One Meridian Plaza in Philadelphia. Both of these buildings had designs quite different from WTC.
Overall, I'd rate this part of the presentation as an A-. I think his points were very effective, although he could have also referenced the 1967 McCormick Center fire in Chicago, and he could have pointed to the lack of seismic evidence for explosions.
After the talk, there were some questions from the audience. One questioner asked him if he considered the "geo-political context" for 9/11. To his credit, Craig said that this was not his area of expertise; he is a fire and explosives expert, and his job is to look at the hard evidence, not speculations about motives.
Another questioner suggested that the Towers were brought down by some high-tech explosive invented by the government but unknown to everyone else. Craig found this suggestion (and a similar suggestion that "lasers" were used) ridiculous, saying that he regularly attends explosives conferences and such a thing could not be kept secret from experts.
Another questioner brought up the collapse of WTC 7. Craig said that he did not know for sure the cause of the collapse of that building, because not enough evidence was gathered yet. He said that he expects we will eventually know, because there is a strong motivation by architects, engineers, and insurance companies to understand the reasons behind the collapse, and many people are working on it.
I'd rate the question-answering portion as B+. Sometimes he simply reiterated previous points, instead of attempting to address the question from another angle, but overall he was generally effective.
Overall, I thought Ron Craig did a good job of demolishing the bizarre and unsupported claims by truthers that explosives brought down the World Trade Center buildings. Regrettably, it is unlikely to have much impact on truthers, who typically hold their beliefs with a religious fervor.
