from the Popular Mechanics "debunking" article on 9/11:
http://www.popularmechanics.com/science/defense/1227842.html?page=1&c=y"NIST researchers now support the working hypothesis that WTC 7 was far more compromised by falling debris than the FEMA report indicated. "The most important thing we found was that there was, in fact, physical damage to the south face of building 7," NIST's Sunder tells PM. "On about a third of the face to the center and to the bottom--approximately 10 stories--about 25 percent of the depth of the building was scooped out." NIST also discovered previously undocumented damage to WTC 7's upper stories and its southwest corner."
Curiously, the damage Sunder describes is not documented in any way, there are no videos or pictures of this "scooped out" section.
But here is what I don't understand: if the lower front of building 7 was seriously compromised by debris damage from the WTC1 collapse, how did the building undergo this perfect symmetrical even collapse?
Why didn't the building lean and tip over on its front, since presumably the supporting columns were damaged on that side, low down, exactly where most of the weight would be bearing on them?
But instead the building goes straight down.
Sunder seems to be saying that if you were sitting on a chair, and someone bashed one of the legs out, rather than the chair tipping over towards the damaged side, the other legs cannot take up the weight and so they suddenly fail evenly, making you fall straight down.