I just had the chance to look at these and they are very fine pieces of animation and alot of work must have been put in, but the pieces that are used to put this together are not secured very well. The towers were rigid, not able to shake as much as those animations show. I'm also sure that if each floor of those "buildings" was an actual floor it would be a total different collapse.
Also, I know it's a slowmo and not to scale of the towers, atleast I don't think it is, did you see how long it took? See, friction/materials prevent free fall, so obviously something was done to the tower so that the falling section was on the ground in ~10seconds, near free fall speed. The remaining tower was a solid structure, a mesh of steel and concrete floors, 40+ interior columns that got thicker as the got nearer the bottom.
Both explinations I heard today for what happened the top section of each tower seem wrong to me. One is it fell apart as it got to the closer to the bottom but still kept its strength, enough to crush the rest of the tower and two is it stayed intact, crushed the rest of the tower and then collapsed itself once reaching the ground. Both contradict each other and both seem to be impossible. A bunch of debrit falling and not just falling straight down, some getting thrown outwards, still has the strength and force to crush columns which are standing straight up and rigid, it's not right.
And then the other, it stays together... unreal. How can it stay together and crush an object made of the same materials but 4 or 5 times the size of it? I understand it's falling but shit doesn't just disintegrate on impact allowing it to continue falling close to free fall. I know atoms aren't actually solid objects but this is taking the biscuit, 1/4 or 1/5 of a structure can go through the other 3/4's or 4/5's and nearly free fall speed and through the path of MOST resistance... amazing how anyone can believe that. I could totally understand if it was the other way round, 4/5's crushing 1/5, but this is incomprehensible.
EDIT: Ok, I just found this video on youtube. It tries to duplicate what happened. Not totally the specs of the towers and not a strong as the towers were, but it is a more accurate experiment than any computer generated animation I have seen yet. It goes with what I was saying, 1/5 of any structure would find it very hard to totally crush the other 4/5's of the structure by falling the distance the tops of the towers fell, or to scale of that distance. And as one of the comments said, why can't they just build a scaled down replica of the towers and see how it falls with the affects of fire and gravity?
If you still feel that the way the towers fell was not influenced by any other force except fire and gravity after watching this, then I don't think you will ever understand this even if it is common knowledge. Here's the video - http://www.youtube.com/watch?v ... NIBys&feature=related