Not particularly accurately.
David Chandler forced NIST to admit "free-fall"
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NoahFence
Banned
Lol...
Of course not.
Of course not.
I though I'd read elsewhere that Chandler made some basic errors in this video but after some time searching didn't find anything concrete. Can someone go over what mistakes, if any, he made. I know his assumption that that FF for a few seconds proves CD, iwas wondering about less obvious problems w/ his analysis.
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LSSBB
Devilish Dictionarian
The two obvious errors are:
- With measurement error taken into account, you cannot say with certainty whether acceleration at any time stayed exactly g
- The leverage from the internal collapsing members can add enough force to balance or exceed the residual resistance from the exterior columns once they fail, giving a net result that can equal or exceed g.
IMNSHO, his most important mistakes were not the analytical ones he made. Although, he made enough of those.
His most important mistakes were:
1. thinking that his experience as a high school (read "very simple") physics teacher qualified him to analyze competently, & opine authoritatively on, a far more complex problem that is entirely out of his field. That is, to opine on the collapse of a uniquely designed 47 story building, which resides in a tiny nook (failure modes & effects) of the field called Structural Engineering.
2. working in isolation, without competent collaborator(s).
3. Despite advice to the contrary, refusing to bring his nonsense to a competent reviewer.
His main errors are ego-driven.
His technical errors aren't as interesting, but include the following:
4. mistaking the external wall of the building for the whole building.
5. performing a linear regression of his velocity data in order to calculate acceleration. This action alone artificially forces his results to conclude "a constant acceleration". A more detailed analysis of the data shows that this conclusion is erroneous. (The fact that his conclusion is erroneous is clearly evident in his own data, if you know what to look for.)
The fact is that the north wall of WTC7 falls "at G" for NO duration. It passes thru G about 4 times, but dwells there for no time at all.
6. Not performing an error analysis. Failure to provide this would get a college freshman engineering (or physics) student a failing grade.
There is more, but that's enough.
His results are incorrect.
The accusations he hurls at the conscientious, competent engineers who did the NIST report are despicable.
His most important mistakes were:
1. thinking that his experience as a high school (read "very simple") physics teacher qualified him to analyze competently, & opine authoritatively on, a far more complex problem that is entirely out of his field. That is, to opine on the collapse of a uniquely designed 47 story building, which resides in a tiny nook (failure modes & effects) of the field called Structural Engineering.
2. working in isolation, without competent collaborator(s).
3. Despite advice to the contrary, refusing to bring his nonsense to a competent reviewer.
His main errors are ego-driven.
His technical errors aren't as interesting, but include the following:
4. mistaking the external wall of the building for the whole building.
5. performing a linear regression of his velocity data in order to calculate acceleration. This action alone artificially forces his results to conclude "a constant acceleration". A more detailed analysis of the data shows that this conclusion is erroneous. (The fact that his conclusion is erroneous is clearly evident in his own data, if you know what to look for.)
The fact is that the north wall of WTC7 falls "at G" for NO duration. It passes thru G about 4 times, but dwells there for no time at all.
6. Not performing an error analysis. Failure to provide this would get a college freshman engineering (or physics) student a failing grade.
There is more, but that's enough.
His results are incorrect.
The accusations he hurls at the conscientious, competent engineers who did the NIST report are despicable.
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DGM
Skeptic not Atheist
No, NIST never said "at". That would imply that it was accelerating at a constant rate. It wasn't so, they didn't. It's that simple.
AsbjornAndersen
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Hi!
They actually did, page 602: "The north face descended at gravitational rate, as exterior column buckling progressed, and the columns provided neglible support to the upper portion of the north face".
"The north face" seems to be confused with "the building" by others, from time to time.
DGM
Skeptic not Atheist
You are indeed correct. (I should have qualified my statement)
They also state that "For discussion purposes, three stages were defined". Their data does not support "at" so hence the qualification. (engineers are funny).
Personally, I think NIST should have ignored the whole thing as it has no bearing on the scope of their investigation. The building had already failed (some 10 seconds before)
BTW: Welcome AsbjornAndersen!
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AsbjornAndersen
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They also state that "For discussion purposes, three stages were defined". Their data does not support "at" so hence the qualification. (engineers are funny).
Personally, I think NIST should have ignored the whole thing as it has no bearing on the scope of their investigation. The building had already failed (some 10 seconds before)
BTW: Welcome AsbjornAndersen!
I even missed the "for discussion purposes"
But yeah, it is really outside of their objective, and it's impossible to do an accurate measurement anyway. The thing the boggles my mind is, the original argument for CD was "It falls entirely in free fall". When that got proved wrong, it became "AHA! It *enters* free fall!", although I have yet to hear an explanation of why this is supposed to be weird. I think maybe Griffin has sown the idea that free-fall only takes place when there is completely empty space below an object. It certainly sounds like that, when I argue this with some people. He even semi-quotes NIST for writing "a miracle happens" - that certainly only happened in his own head.
I have been offered a free copy of his WTC7-book, but since I had to check (and refute) every single quote just for his WTC7-article, I have reasoned it would simply take too long, and not many facts would come out of it anyway.
DGM
Skeptic not Atheist
To a certain extent he's right.
The problem is (as you alluded to) the accuracy of the measurements. femr2 has done a much better job at tracking this than anyone (my opinion).
No one has shown that there was no resistance (empty space). I don't remember exactly how NIST said it but it was something along the lines of "minimal resistance".
Anyway you slice it. There really was no evidence of demolition.
Oystein
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"Performing a linear regression of his velocity data" means answering the question "which straight line fits best through the plot of measured velocity data".
Because that question asks specifically for a straight line, the reslut will be a straight line. Acceleration is the first derivative of velocity, and the first derivative of a straight line for velocity is a constant acceleration.
This method of "performing a linear regression of his velocity data" will get you a straight line, no matter what the shape of the actual curve is. Suppose the velocity plot describes a perfect parabola: Then in reality, it would have to be described by steadily increasing (or decreasing), as opposed to constant, acceleration. However you can still run a linear regression on the parabola data, and that gets you a straight line, by definition. You can run a linear regression on a dog-shaped velocity curve or on one that goes zick-zack or is totally random, you get a result of straight velocity line and constant acceleration.
So that's what tfk means when he says Chandler "forces his results to conclude a constant acceleration": His method cannot get any other result, no matter what the actual behaviour of acceleration is. Chandler does linear regression, and the result of linear regression is always a line.
It's simply not the right method to use.
AsbjornAndersen
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Crap, my entire message disappeared...
Cutting myself short, I find the idea in Chris Mohr's movie with the failed elements pulling(!) the wall down with the still-attached girders to be quite plausible. Also because I'm no structural engineer, so "big mass pulling already falling other mass to greater speed" makes sense to me But I wonder if it's even possible to get beyond speculation in regards to the inner workings of the collapse?
The demolition-idea is extremely absurd, and the disregard for expert-testimonies and missing evidence like the resulting massive sound pressures, is mind-blowing. The fact than anyone can be blind to the obvious manipulations of videos and quotes, even when pointed out directly, is really beyond me.
Cutting myself short, I find the idea in Chris Mohr's movie with the failed elements pulling(!) the wall down with the still-attached girders to be quite plausible. Also because I'm no structural engineer, so "big mass pulling already falling other mass to greater speed" makes sense to me
But I wonder if it's even possible to get beyond speculation in regards to the inner workings of the collapse?The demolition-idea is extremely absurd, and the disregard for expert-testimonies and missing evidence like the resulting massive sound pressures, is mind-blowing. The fact than anyone can be blind to the obvious manipulations of videos and quotes, even when pointed out directly, is really beyond me.
ergo
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Asbjorn, can you identify the instances in Newtonian mechanics where free fall occurs through non-empty space? Would very very much love to hear about this!
DGM
Skeptic not Atheist
So your claim is everything for 8 floors was vaporized. Funny, I can't find video evidence of this.Asbjorn, can you identify the instances in Newtonian mechanics where free fall occurs through non-empty space? Would very very much love to hear about this!
Your turn. Where's the video evidence that 8 floors of the building simply disappeared?
Get back to us on this.
Where on earth is there empty space?Asbjorn, can you identify the instances in Newtonian mechanics where free fall occurs through non-empty space? Would very very much love to hear about this!
Wait,...
http://www.internationalskeptics.com/forums/showpost.php?p=6263596&postcount=621
You better take a powder on this one.
...
Too late.
LSSBB
Devilish Dictionarian
Asbjorn, can you identify the instances in Newtonian mechanics where free fall occurs through non-empty space? Would very very much love to hear about this!
Are you trying to say nothing ever accelerates going downward? 9.81 m/s2 is an acceleration, why would nothing ever reach it while collapsing?
AsbjornAndersen
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Asbjorn, can you identify the instances in Newtonian mechanics where free fall occurs through non-empty space? Would very very much love to hear about this!
Yeah, I should of course have written "acceleration equivalent to free fall". What Griffin implies IMO is that this acceleration can only take place in case empty space/free fall, and that is what I objected to.
I elaborated in the subsequent post (also about my admittedly limited knowledge of constructions btw
) that (I find it plausible) an attached weight would help accelerate the falling object. So no need for floors to evaporate, just a sufficiently limited resistance below these. Of course, I could be totally wrong, in which case I'd like to be enlightened
BasqueArch
Graduate Poster
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NIST before Chandler
The upper 18 stories took 40 percent longer to fall than free fall time.
NIST after Chandler
The upper 18 stories took 40 percent longer to fall than free fall time.
-------------------------------------------------------------------------------
NIST NCSTAR 1-9 Vol2 for Public Comment (Draft Aug 2008)
SUMMARY OF FINDINGS
“Thus, the actual time for the upper 18 stories to collapse, based on video evidence, was approximately 40 percent longer than the computed free fall time and was consistent with physical principles. “
http://www.nist.gov/customcf/get_pdf.cfm?pub_id=909257
NIST WTC7 FINAL - 1A Report (Final November 2008)
SUMMARY
"The observed descent time of the upper 18 stories of the north face of WTC 7 (the floors clearly visible in the video evidence) was 40 percent greater than the computed free fall time.
A more detailed analysis of the descent of the north face found three stages: (1) a slow descent with acceleration less than that of gravity that corresponded to the buckling of the exterior columns at the lower floors, (2) a freefall descent over approximately eight stories at gravitational acceleration for approximately 2.25 s, and (3) a decreasing acceleration as the north face encountered resistance from the structure below."
http://www.nist.gov/customcf/get_pdf.cfm?pub_id=861610
The lower columns buckled and at a small angle the splices failed, then the building fell with no resistance.
It is at this point, after the outside walls were collapsing, that Chandler claims the bombs went off. At all the exterior columns. There was no need.
Exterior columns shown buckled, failed splices.
NIST’s velocity graph showing first stage of less than FFA. (Downward velocity shown as positive.)
Chandler’s velocity graph showing NIST’s first stage of less than FFA. (Downward velocity shown as negative)
NIST before Chandler
The upper 18 stories took 40 percent longer to fall than free fall time.
NIST after Chandler
The upper 18 stories took 40 percent longer to fall than free fall time.
Lower columns buckle, column splices fail, building wall falls unresisted at FFA. Chandler's silent bombs go off too late, they should have gone off before the building began to fall.
The upper 18 stories took 40 percent longer to fall than free fall time.
NIST after Chandler
The upper 18 stories took 40 percent longer to fall than free fall time.
-------------------------------------------------------------------------------
NIST NCSTAR 1-9 Vol2 for Public Comment (Draft Aug 2008)
SUMMARY OF FINDINGS
“Thus, the actual time for the upper 18 stories to collapse, based on video evidence, was approximately 40 percent longer than the computed free fall time and was consistent with physical principles. “
http://www.nist.gov/customcf/get_pdf.cfm?pub_id=909257
NIST WTC7 FINAL - 1A Report (Final November 2008)
SUMMARY
"The observed descent time of the upper 18 stories of the north face of WTC 7 (the floors clearly visible in the video evidence) was 40 percent greater than the computed free fall time.
A more detailed analysis of the descent of the north face found three stages: (1) a slow descent with acceleration less than that of gravity that corresponded to the buckling of the exterior columns at the lower floors, (2) a freefall descent over approximately eight stories at gravitational acceleration for approximately 2.25 s, and (3) a decreasing acceleration as the north face encountered resistance from the structure below."
http://www.nist.gov/customcf/get_pdf.cfm?pub_id=861610
The lower columns buckled and at a small angle the splices failed, then the building fell with no resistance.
It is at this point, after the outside walls were collapsing, that Chandler claims the bombs went off. At all the exterior columns. There was no need.
Exterior columns shown buckled, failed splices.
NIST’s velocity graph showing first stage of less than FFA. (Downward velocity shown as positive.)
Chandler’s velocity graph showing NIST’s first stage of less than FFA. (Downward velocity shown as negative)
NIST before Chandler
The upper 18 stories took 40 percent longer to fall than free fall time.
NIST after Chandler
The upper 18 stories took 40 percent longer to fall than free fall time.
Lower columns buckle, column splices fail, building wall falls unresisted at FFA. Chandler's silent bombs go off too late, they should have gone off before the building began to fall.
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