Watch Out for Undocumented Assumptions
One trick that the 9-11 Deniers use a lot of is undocumented assumptions. Here's a classic example from a post over at Democratic Underground:
In discussions about physical evidence, specifically about the way the towers fell, the underlying question is whether it's possible for a steel-frame structure to fall in this way -- that is, at nearly free-fall speed -- under any circumstances other than controlled demolition. It seems the structure would have too much strength to collapse so quickly into so many pieces while so much of the energy that would be needed to make that happen was dissipated in other ways.
The usual answer is "Of course it's possible."
So my question to you is this: Can you document any other case of a steel-frame high-rise structure collapsing at nearly free-fall speed, that is, within twice the time that free fall would have taken?
What's the undocumented assumption, class? That's right, the person asking the question is hoping that nobody will notice the assumption that a controlled demolition comes down at "free-fall speed". What they really mean is in free-fall time, or at free-fall acceleration, but more important, they never seem to test this. Look at the Southwark Towers, for example. This is a demolition that is recommended by many 9-11 Deniers as illustrative of a classic controlled demolition; Professor Steven Jones cited it in his Why Indeed Did the WTC Buildings Collapse paper.
Watching carefully (click on the third icon from the left on the bottom row to see this demolition), I estimated that the roof on the left building started sagging right around 38.24 into the movie, and that the top of the building hit ground at about 45.69. I found it easiest to pause the film and move the slider back and forth to estimate the times.
Thus the duration of the collapse was about 7.45 seconds. From this page we know that the roof of the building was about 98 meters high, or approximately 323 feet. But a building of 323 feet should not take 7.45 seconds to collapse in free fall, it should only take 4.5 seconds by the formula 16*4.5^2=323. Therefore, the Southwark Towers did not collapse in free-fall time.
This video also demonstrates the nonsense about pyroclastic flows supposedly being indicative of controlled demolition. In fact, the pyroclastic flows are just dust being stirred up rapidly by the sudden movement of large objects through the air--like a 26 story building collapsing nearby. There are minor puffs of smoke from the explosions, but they are nothing compared to the dust that the collapse brings up. How can the Deniers pretend otherwise?