Sorry Zi, I'll try harder next time

Originally posted by: Zoso471
I disagree, there is a distinct difference between something exploding and something snapping or breaking. but ok, lets say there wasnt an explosion, that still leaves the virtually impossible chance that all pillars gave out at the same time. remember the tower didnt collapse to the left or right, it collapsed parallel, straight onto itself, meaning all pillars had to have given out at the exact same time.
No, it does not require what you're suggesting, at all. It's not like building a structure out Jenga blocks, where a failure causes it to topple sideways. Or felling a tree. Real, interconnected structures do not fail that way.
In this case, we're talking about a specific phenomenon called "buckling". If one column is able to buckle, or otherwise fails, then the rest of the columns are suddenly supporting a higher load than they were designed for. If they've also been damaged, then it's possible that they too, will buckle. This can happen pretty quickly, certainly within the time frame of the collapse of Tower 7.
As for the direction of collapse, other than internal stresses, the only force acting on the building is gravity...last time I checked it basically pulls straight down. There will be some slight bias based on which column failed first (assuming it wasn't toward the center, which isn't necessarily a good assumption, depending on how the fire damage occurred), but if the columns all fail within less than a second of each other, then it would be pretty hard to determine any direction of fall from the ensuing rubble.
Basically, the point I'm trying to make, if you are willing to think clearly about it, is that once you exceed the failure point of complex structures, lots of things happen that are not intuitive to those who are not studied in the subject. Furthermore, structures can fail very quickly. Look at any bridge collapse. To any eye the major components may appear to fail simultaneously. But the truth of the matter is that solids transfer load nearly instantaneously (with an imperceptible lag that is on the order of their stiffness coefficient) and as a result, what starts as a single-point failure can radiate out quickly, especially if the entire structure has been compromised in the first place (in this case, lots of metal structure having its structural properties reduced by high heat).
Originally posted by: Zoso471
i agree, first hand recollection are not the greatest, especially years after the event, but there still is a lot of video and a lot of audio recording. and when numerous different people all give the same account (ie. that they heard 3 explosions in the north tower, one of which seemed to come from the basement), then there is some truth behind it.
Think about how many people each of these witnesses talked to before they were interviewed, and the way interviewers phrased questions. It's very easy to fill voids with false memories, or to convince yourself of one thing, or another.
Regardless, you could have 5,000 New Yorkers who work in the financial district claim they heard what they thought was an explosion during the building collapse, and it would mean that a single one of them actually knew what happened, just what they thought it sounded like.
Believe me, when I say that the energy released from a structure that large when it buckles will sound like an explosion straight out of a movie. All an explosion sounds like is a huge noise with a relatively low frequency. It doesn't have any kind of unique tone or quality to it...just a BOOM, accompanied with the sound of whatever shrapnel it generates hitting everything around it.
If you have an engineering degree of any sort, then I'm willing to entertain your opinion about "snapping" vs "breaking" vs "exploding" sounds being generated by structural failures. But personally, I've witness structural tests of metal structures that were tested to failure, and it can be really loud when they break. It's very straightforward to extrapolate those observations to a building that is hundreds, or even thousands of times more massive than the structures I'm talking about.