[CORed]

Here's the sequential mechanism. One floor collapses 70 or 80 floors up, The entire weight of the part of the building above that floor falls into the floor below, then the floor below that one, etc. until the whole thing is a pile of rubble on the ground.

Regarding the claim that the fire couldn't have caused the collapse: Remember the gas truck that burned under the bridge in Oakland a few weeds ago, resulting in the collapse of the (at least partly steel) bridge? The people on these silly-ass web sites telling you that the fire couldn't cause the building to collapse (especially after it was damaged by the impact of the plane) are full of crap. No, I didn't read the site your linked to, and I'm going to. However, on similar sites that I have read, it usually takes only a few paragraphs to tell that they have no clue what they are talking about. They will spout a lot of gobbledygook that looks impressive to people lacking in scientific training and critical thinking skills, but which is obviously [censored] to anybody who has them.

The world trade center collapsed because two planes hit the towers and caught fire inside them. Probability 99.9999999%.

Was there a cover up? Most likely. Cover up is the Bush administration's natural mode of operation, even when there is nothing to cover up, or (most commonly) nothing to cover up except their incompetence, which they inevitably fail to cover up, because they're too incompetent to conduct a cover up. See U.S. attorney firings: Only the Bush administration could turn something they had every right to do into a scandal. All they had to say is "We fired them because we didn't like them". Instead, they had Gonzalez claiming he knew nothing about why his own employees were fired, and changed their story 7 or 8 times. Now, do you really think think Larry, Moe and Curly -- Oops! I mean Dubbaya, Dick and Rummy, were smart enough to stage a fake terrorist attack and get away with it? I don't