>> 4. Similarly the fact that the building started falling with almost perfect verticality implies that, once the moment of collapse arrived, ALL remaining columns must have failed simultaneously.

I am glad to see you say: “The exterior of the building fell ALMOST vertically. Therefore it is safe to say that the remaining columns must have failed ALMOST simultaneously.” It seems at last we are getting somewhere.

Then our positions diverge because you say: “If you look at NISTs model of the collapse you will see that the interior collapse did indeed remove large sections of the exterior columns. Once the exterior columns buckled there was very little in the way of resistance until the top half of the building met the lower parts which were still intact.”

I am glad you brought that up. It is only a model you must remember - it is not an observation. For collapse to be due to buckling, buckling would have to happen first. There would be an early buckling phase where the resistance would be high and motion slow, then, as the buckling progressed to wider angles, the resistance would decline and the acceleration would increase. If we look at the graph of velocity against time we would see a curve as the acceleration increased, but we do not. We see a little lurch then a straight line for 2 seconds, a 6 storey drop. That is not a model, it is an observation. A straight line velocity graph means no resistance.

http://www.nist.gov/public_affairs/releases/wtc_videos/wtc_videos.html

Thanks for including the above link to the NIST release. It gives the best video I have seen of the collapse of WTC7, as it starts earlier than the one usually displayed. It clearly shows the eastern penthouse dropping while there is no trace of damage to any window in the whole of the visible area of the north face. How you can have all the collapse that NIST produces in the simulation, starting with a section of floor falling, triggering more sections of floors to fall, removing horizontal support to a long length of column 79, exposing it to the risk of buckling, which then buckles, causing many floors higher up to drop, exposing more columns to the risk of buckling, which then buckle, and destroy the support of the eastern penthouse, without a single bit of evidence of distortion of the north wall, strains credulity.

>> 5. Fire, even if severe, cannot be expected to produce loss of strength in every remaining steel column which is both total and simultaneous.

You say that this is “True and irrelevant.”

Glad you agree that it is true. It is not however irrelevant. Your argument rests on the idea that substantial transfer of load to fewer and fewer columns occurs, eventually initiating sudden buckling. But there is only one way in which load can be transferred. It is through distortion of the structure. Only where distortion occurs will force be transmitted. Look at the video – you can see absolutely no sign of distortion – not a window broken, then suddenly collapse occurs – a tiny lurch then free fall acceleration.

It doesn’t matter what explanations are contrived to explain the collapse of WTC7, or who presents them, if they don’t provide an explanation for free fall through 6 storeys, they must be false. This is the key issue. The only explanation presented so far which can account for observations is explosives. Every other point of discussion is a distraction

Amoeba,

You say >> “you will see a clear white flash as part of the western penthouse falls away toward the east. What can make a white flash?

As an educated person you would know that a) many things can cause a white flash b) the collapse of the western penthouse was not initiated anywhere near the roof. The collapse of the penthouse occurred because of the failure of supporting columns way down in the building.

You say >> “For 2 whole seconds there was nothing that could be described as “progressive”. The top fell through 6 storeys during these 2 seconds and it encountered no detectable resistance… How could there be nothing there to hit. “

First of all, the stories were 4m high so that means only 5 stories, Secondly, the nist analysis shows the majority of the interior collapsed before the exterior collapse begins. The exterior columns then buckle at about the 7th floor and there is about a 5 story height before the upper parts of the building meet the lower parts.
http://www.nist.gov/public_affairs/releases/wtc_videos/wtc_videos.html

you say >> “What matters is that NIST’s falsification, in that it has obscured the existence of free fall, has been exposed and we have the correct rate of fall for 2 seconds.

NO absolutely not. If you offered Chandlers’ video as evidence in a trial, you would be laughed out of court. His analysis is primitive, at best. I won’t pretend that it doesn’t raise questions, but to suggest that this is definitive is, as you put it above, very poor analysis.

There are a couple of major problems with the video.

a) The time frame. Is it actually the time he says it is
b) The distances. Are they the distances he claims.

TBC

TBC

The accuracy of the time scale depends initially upon the capture speed being known, was the footage originally 60i or 50i or 30p etc, and accurate. The image used by Chandler has been compressed and posted to you tube which further removes information from the footage. Chandler takes his measurements from playback of this grainy footage. He calibrates the system using the known width of the building, yet his footage is shot from an angle, although what angle we don’t know. And the extent to which the shot is squashed or stretched is unknown. How he calibrates the time I don’t know. Finally, in all of this, we rely on his honesty and accuracy.

If you are an engineer or scientist, you would know that this experiment is nowhere near the standard required in order to be accepted for peer review. It’s pop science of exactly the type you might expect from a high school physics teacher trying to entertain his class. It is not SCIENCE.

What’s obvious from the vast majority of the papers written by the “truth” movement is that they are not written by structural engineers. Why is that do you think? What is your background by the way?

Your position relies upon the complete accuracy of Chandlers calculations. Yet you linked me to a truther site which only calculated 9.1 m/s2. Without actual free fall acceleration, your whole case falls apart.

Why hasn't an actual engineer looked at this issue and done some real work that is of peer review standard?

Paul.L wrote, "If you are an engineer or scientist, you would know that this experiment is nowhere near the standard required in order to be accepted for peer review."

Presumably Paul.L would have us believe that the method used in the NIST report of calculating just one overall average rate of acceleration, commencing seconds before the outer wall began to collapse, is of a higher standard than calculating the speed and acceleration of collapse during each of a larger number of smaller intervals in http://au.youtube.com/watch?v=gC44L0-2zL8

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Regardless of whether WTC7 fell five or more stories at free fall speed, or only four stories as Paul.L insists, the fact remains that this can only be explained if explosives were used to suddenly and simultaneously remove all the supports of the outer wall.

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Actually, Paul.L and amoeba, I thought the time period over which free fall was observed was 2.5 seconds and not 2 seconds.

Dagget,

I think we have already proved the point that you aren't even close to being qualified to comment. Frankly you don't know what you are talking about most of the time.

If you even read my last posts you will see that I do not accept Chandlers video as conclusive evidence. No real scientist would either. It is not nearly comprehensive enough.

>> "Presumably Paul.L would have us believe that... "

The fact that you would then attempt to draw conclusions about how I felt about NIST's tests is typical, but this is ENTIRELY fallacious. How about you stop presuming what I think, you are really not very good at it.

I haven't seen NIST's examination of the buildings acceleration so I can't comment.

Finally NISTs models of the building collapse shows that the building would have been falling at close to free fall speeds for a couple of seconds after the start of the exterior collapse. The truther website Amoeba linked me to measured the acceleration to be 9.1m/s2. I think that is much more likely to be the correct value.