So far we have established that cars cannot drive through brick walls at the same speed as if they were driving through an open gate. (See Can a car drive through a brick wall...) and that their momentum will be slowed by the impact of the brick wall. This demonstrates our understanding that the movement or acceleration of objects meeting other objects in their path will be altered in some way, slowed or halted altogether.
There seems to be still some debate here, though, that gravitational pull is much more powerful than anything that might be propelled by an engine. There seems to still be a belief, still unsupported by any known scientific principle, that gravity can pull objects through other objects of equal or greater density at the rate or near the rate that it will pull an object through air.
Just in case anyone here doesn't understand the argument being presented: the official explanation offered by NIST and promoted in popular media for the collapse of the Twin Towers (and WTC7) is that the upper floors of the towers, above where the planes crashed, crushed through the remaining intact building below the fire zones at a speed which is evidenced in all video footage to be at the rate of free fall, or within seconds of it.
Various arguments that have been presented here at Babble or in official story venues to explain what is not explainable by any known scientific principle include:
the speed of collapse was “nowhere near” free fall, being up to four seconds longer than free fall. This argument, in essence, asks us to believe that 91 and 78 floors respectively of the Twin Towers produced only 1- 4 seconds of resistance to the descending upper mass of floors. This argument also cannot explain at what point this descending mass of floors was pulverized in its descent (as there is no visual evidence of any significant pancaking having occurred). Was it on the way down, or did it get “crushed up” at the bottom, as the “crush down, crush up” theory suggests?
If it is the latter, then the “crush down, crush up” theory asks us to suspend our disbelief in the possibility of these descending blocks of floors to maintain their mass while pulverizing 91 or 78 levels of intact building (at the rate it would take for a brick to drop the same distance through air), and only at the bottom would it be pulverized in meeting the ground, but actually not even then, as we know that the buildings collapsed into their basements.
That fires caused the structural weakening that allowed all three buildings to disintegrate in a manner that professional demolitioners compare to controlled demolitions. The fire theory is also NIST's best explanation for the collapses, despite FEMA's earlier suggestion that this theory only had a “low probability” of being correct. The pancake fire theory suggested that the joints which held the trusses (which held the floors) to the core columns through the entire height of the buildings were all weakened by the upper floor fires, which, in the Twin Towers, lasted less than 90 and 60 minutes respectively. And furthermore, that these joints which held the floors to the columns all disassembled themselves simultaneously, so as to create the global lack of resistance that we witnessed in the video footage of the collapses. This theory is not supported by NIST and haas in any case been debunked. The NIST fire theory talks vaguely and briefly about floors sagging and pulling in the perimeter columns, which stress the core columns and vice versa. No one has seen NIST's computer modelling of this hypothesis and many doubt it (eg; article in New Civil Engineer) Whatever fire theory is used does not explain the disintegration of the building's core, which, by its design, would not collapse or disintegrate the way theoretically pancaking/crushing floors would.
These are the main arguments that still remain to explain the never-before-witnessed-in-history rapid disintegration of three, modern, steel-mesh-frame skyscrapers. If I have missed any significant argument here, please feel free to correct me.
I would like to use this thread to examine these specific arguments and also, hopefully, to investigate why people who invoke science and scientific empiricism in other topics of hot debate seem so willing to avoid any serious, plain-language, eyes-open look into the absence of science in their arguments on this subject. We have yet to see anyone here on Babble confirm for us what principle of physics explains the lack of resistance we witness in the rapid disintegration of the towers. (Shouldn't this be easy if the official explanation is so “obvious”?) The only principle that we know about is that for a building (let alone three) to disintegrate in that manner and at that speed can only mean that the bulk of the building presented no resistance to its own descent; in other words, something else was used to remove that resistance. In controlled demolition, it is explosives. What was it in the case of the WTC?