# An angle of the WTC collapse I'd never seen
**URL:** https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182
**Category:** Great Debates
**Created:** [July 19, 2010, 1:39am UTC](https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182 "2010-07-19T01:39:32Z")
**Posts on this page:** 20
**Page:** 23
### Author:  [@ivan\_astikov](https://boards.straightdope.com/u/ivan_astikov)
#### Post date: [July 25, 2010, 5:18pm UTC](https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182/441 "2010-07-25T17:18:58Z")
> [@Mr.Miskatonic](#):
>
> > [@ivan\_astikov](#):
> >
> > Here’s a typical piece of NIST bullshit that even an idiot like me can rip apart.
>
> Except that you fail to do so.
>
> > [@](#):
> >
> > So, the seismic record didn’t even detect the impacts of the planes!
>
> Umm, it did.
>
> [911myths](http://www.911myths.com/html/seismic_record.html)
>
> Look at the first graph. They were recorded.
>
> > [@](#):
> >
> > How the fuck were they meant to detect much smaller charges intended to just blow up specific columns?
>
> Because that is what they do?
So, why doesn’t NIST’s own website correct that little error? A bit shoddy, don’t you think? Makes you wonder where else they applied shoddy work.
[World Trade Center Investigation | NIST](http://wtc.nist.gov/pubs/factsheets/faqs_8_2006.htm)
It’s right there in reply to question #5.
---
### Author:  [@CannyDan](https://boards.straightdope.com/u/CannyDan)
#### Post date: [July 25, 2010, 5:20pm UTC](https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182/442 "2010-07-25T17:20:18Z")
> [@ivan\_astikov](#):
>
> > [@CannyDan](#):
> >
> > But it certainly doesn’t mean that explosives were actually involved. Clearly, it would be impossible to hide the amount of explosives necessary to bring down a building, to say nothing of hiding the preparations necessary to making those explosives effective. As has (sigh) been said so many times, by so many others, before.
>
> Go on, keep repeating the lie. First of all, we’ve already stated that we are not talking about a conventional controlled demolition, hence your bollocks about it requiring too much explosive and preparation is completely misleading.
>
> You should also check up on how many people had access to the WTC buildings involved, in say the month prior to it happening. Big hint - there was a lot, and it wouldn’t be too difficult too go unnoticed in such a large building. Not that they couldn’t also have had fraudulent ID, if they were challenged.
No, you keep shoveling the shit.
Of course, tens of thousands of people had access to the WTC buildings. They were _giant office buildings_ for crying out loud. But your scenario requires some kind of un-“conventional controlled demolition”, meaning what exactly? Some super secret explosive with a thousand times the energy of C4? Something so powerful that a piece the size of a sugar cube is equivalent to a case of plastique? And so some proportion of those tens of thousands of people come bearing sugar cubes, wandering into your own office, and those of your colleagues, indeed into offices all over the building, stacking sugar cubes in corners or balancing them on shelves. Leaving them in the ashtrays by the elevators, and maybe behind the lavatories, because they are so powerful that they don’t really need to be placed in actual contact with the supporting structures of the buildings, right? And nobody notices, nobody comments on it, water cooler talk doesn’t mention the piles of sugar cubes in every corner of the building.
And of course all the hordes of people planting these cubes must know in advance to stay home on “the day”, right? And they must all be blithely uncaring about the fate of their fellow workers, right? Surely nobody would rat out the conspiracy, would they?
Then, on the appointed day and time, not too long after airplanes actually crashed into the buildings, all these carefully placed sugar cubes are somehow detonated by – what? Psychokinesis? Gravitronic rays? Plain old magic? Because nobody bothered to connect them all with the miles of wire or det cord that every other demolition actually requires.
This new and marvelous technology, both the sugar cube explosives and the wireless and receiverless detonation control system, are so super secret that they are used only for the public destruction of significant landmarks into which huge aircraft have been flown at cruising speed.
Color me unimpressed with your particular conspiracy theory. But highly impressed with your imagination.
---
### Author:  [@Mr.Miskatonic](https://boards.straightdope.com/u/Mr.Miskatonic)
#### Post date: [July 25, 2010, 5:22pm UTC](https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182/443 "2010-07-25T17:22:32Z")
> [@ivan\_astikov](#):
>
> Does it make less or more sense than the NIST comment I’ve quoted above? Remember, I’m just a layman; they have all the degees and letters after their names.
You are misreading the words you redded out:
“There were no seismic signals that occurred prior to the initiation of the collapse of either tower”
Now when they say prior, they do not mean ‘no signals before collapse, ever’ they simply mean that just prior to collapse there were no spikes. Ergo no evidence of explosives was found in the seismic record.
Even without context this is pretty obvious. In context, where you realize that NIST is responding to people claiming that the seismic record showed spikes just before the collapse of the building.
---
### Author:  [@ivan\_astikov](https://boards.straightdope.com/u/ivan_astikov)
#### Post date: [July 25, 2010, 5:22pm UTC](https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182/444 "2010-07-25T17:22:54Z")
And even accepting that the airplanes impacts were registered, how equivalent to a placed charge would that amount of energy be? Tell me how big a blip a synchronous explosion with x amount of explosives would create?
---
### Author:  [@Mr.Miskatonic](https://boards.straightdope.com/u/Mr.Miskatonic)
#### Post date: [July 25, 2010, 5:24pm UTC](https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182/445 "2010-07-25T17:24:35Z")
[quote=“ivan\_astikov, post:441, topic:547182”]
[quote=“Mr.Miskatonic, post:439, topic:547182”]
> [@ivan\_astikov](#):
>
> So, why doesn’t NIST’s own website correct that little error? A bit shoddy, don’t you think? Makes you wonder where else they applied shoddy work.
>
> [World Trade Center Investigation | NIST](http://wtc.nist.gov/pubs/factsheets/faqs_8_2006.htm)
>
> It’s right there in reply to question #5.
It is not shoddy if you read to comprehend.
---
### Author:  [@Grumman](https://boards.straightdope.com/u/Grumman)
#### Post date: [July 25, 2010, 5:27pm UTC](https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182/446 "2010-07-25T17:27:30Z")
> [@ivan\_astikov](#):
>
> So, why doesn’t NIST’s own website correct that little error? A bit shoddy, don’t you think? Makes you wonder where else they applied shoddy work.
It’s not an error to omit blatantly obvious information that is irrelevant to the question. The question was about non-existent spikes indicating the use of explosives just prior to each collapse, not the impacts almost an hour earlier.
---
### Author:  [@ivan\_astikov](https://boards.straightdope.com/u/ivan_astikov)
#### Post date: [July 25, 2010, 5:33pm UTC](https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182/447 "2010-07-25T17:33:44Z")
> [@Grumman](#):
>
> > [@ivan\_astikov](#):
> >
> > So, why doesn’t NIST’s own website correct that little error? A bit shoddy, don’t you think? Makes you wonder where else they applied shoddy work.
>
> It’s not an error to omit blatantly obvious information that is irrelevant to the question. The question was about non-existent spikes indicating the use of explosives just prior to each collapse, not the impacts almost an hour earlier.
So, now I am asking how big a spike you’d expect to see, had there been explosions prior to the collapses? Also, assuming just for hypothetical sakes that explosives had been used to weaken a specific section of the core below the crash sites, how soon would this have been expected to take effect? Forget about the planes crashing into them, just for the moment, and try and explain what we’d have seen had this been the case instead.
---
### Author:  [@PBear42](https://boards.straightdope.com/u/PBear42)
#### Post date: [July 25, 2010, 5:33pm UTC](https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182/448 "2010-07-25T17:33:48Z")
**ivan** , just because you hit the reply button doesn’t mean you’ve actually replied. This applies not only to your “reply” to my post but all the others in this thread.
---
### Author:  [@Skywatcher](https://boards.straightdope.com/u/Skywatcher)
#### Post date: [July 25, 2010, 5:35pm UTC](https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182/449 "2010-07-25T17:35:02Z")
> [@pedescribe](#):
>
> > [@ivan\_astikov](#):
> >
> > > [@pedescribe](#):
> > >
> > > Do you believe that there were explosives detonated in the Twin Towers on 9/11, or not?
> >
> > It’s certainly less of an impossibility than the book of Genesis being based on scientific fact and that it was dictated to man by a god.
>
> But do you believe it [the explosives being in the towers]or not? Answer the question!
> [@ivan\_astikov](#):
>
> I’m not going to discount it, when NIST themselves have said they didn’t look for any as it was too unlikely an hypothesis.
> [@ivan\_astikov](#):
>
> > [@CannyDan](#):
> >
> > But it certainly doesn’t mean that explosives were actually involved. Clearly, it would be impossible to hide the amount of explosives necessary to bring down a building, to say nothing of hiding the preparations necessary to making those explosives effective. As has (sigh) been said so many times, by so many others, before.
>
> Go on, keep repeating the lie. First of all, we’ve already stated that we are not talking about a conventional controlled demolition, hence your bollocks about it requiring too much explosive and preparation is completely misleading.
And [I’ve already stated](http://boards.straightdope.com/sdmb/showpost.php?p=12719578&postcount=305) that _any_ explosives would have needed to survive the fires. [Again](http://boards.straightdope.com/sdmb/showpost.php?p=12719578&postcount=305): look up what Danny Jowenko says about WTC 1 & 2.
---
### Author:  [@ivan\_astikov](https://boards.straightdope.com/u/ivan_astikov)
#### Post date: [July 25, 2010, 5:38pm UTC](https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182/450 "2010-07-25T17:38:25Z")
From question 6.
> [@](#):
>
> From video evidence, significant portions of the cores of both buildings (roughly 60 stories of WTC 1 and 40 stories of WTC 2) are known to have stood 15 to 25 seconds after collapse initiation before they, too, began to collapse. Neither the duration of the seismic records nor video evidence (due to obstruction of view caused by debris clouds) are reliable indicators of the total time it took for each building to collapse completely.
Another seemingly contradictory paragraph.
---
### Author:  [@ivan\_astikov](https://boards.straightdope.com/u/ivan_astikov)
#### Post date: [July 25, 2010, 5:42pm UTC](https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182/451 "2010-07-25T17:42:24Z")
NIST talking bollocks again.
> [@](#):
>
> 1. Did the NIST investigation look for evidence of the WTC towers being brought down by controlled demolition? Was the steel tested for explosives or thermite residues? The combination of thermite and sulfur (called thermate) “slices through steel like a hot knife through butter.”
>
> NIST did not test for the residue of these compounds in the steel.
>
> The responses to questions number 2, 4, 5 and 11 demonstrate why NIST concluded that there were no explosives or controlled demolition involved in the collapses of the WTC towers.
>
> Furthermore, a very large quantity of thermite (a mixture of powdered or granular aluminum metal and powdered iron oxide that burns at extremely high temperatures when ignited) or another incendiary compound would have had to be placed on at least the number of columns damaged by the aircraft impact and weakened by the subsequent fires to bring down a tower. Thermite burns slowly relative to explosive materials and can require several minutes in contact with a massive steel section to heat it to a temperature that would result in substantial weakening. Separate from the WTC towers investigation, NIST researchers estimated that at least 0.13 pounds of thermite would be required to heat each pound of a steel section to approximately 700 degrees Celsius (the temperature at which steel weakens substantially). Therefore, while a thermite reaction can cut through large steel columns, many thousands of pounds of thermite would need to have been placed inconspicuously ahead of time, remotely ignited, and somehow held in direct contact with the surface of hundreds of massive structural components to weaken the building. This makes it an unlikely substance for achieving a controlled demolition.
>
> Analysis of the WTC steel for the elements in thermite/thermate would not necessarily have been conclusive. The metal compounds also would have been present in the construction materials making up the WTC towers, and sulfur is present in the gypsum wallboard that was prevalent in the interior partitions.
How convenient.
---
### Author:  [@ivan\_astikov](https://boards.straightdope.com/u/ivan_astikov)
#### Post date: [July 25, 2010, 5:49pm UTC](https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182/452 "2010-07-25T17:49:51Z")
And finally.
> [@](#):
>
> 1. Why is the NIST investigation of the collapse of WTC 7 (the 47-story office building that collapsed on Sept. 11, 2001, hours after the towers) taking so long to complete? Is a controlled demolition hypothesis being considered to explain the collapse?
>
> When NIST initiated the WTC investigation, it made a decision not to hire new staff to support the investigation. After the June 2004 progress report on the WTC investigation was issued, the NIST investigation team stopped working on WTC 7 and was assigned full-time through the fall of 2005 to complete the investigation of the WTC towers. With the release and dissemination of the report on the WTC towers in October 2005, the investigation of the WTC 7 collapse resumed. Considerable progress has been made since that time, including the review of nearly 80 boxes of new documents related to WTC 7, the development of detailed technical approaches for modeling and analyzing various collapse hypotheses, and the selection of a contractor to assist NIST staff in carrying out the analyses. It is anticipated that a draft report will be released for public comment by July 2008 and that the final report will be released shortly thereafter.
>
> The current NIST working collapse hypothesis for WTC 7 is described in the June 2004 Progress Report on the Federal Building and Fire Safety Investigation of the World Trade Center Disaster (Volume 1, page 17, as well as Appendix L), as follows:
>
> ```
> *
>
> An initial local failure occurred at the lower floors (below floor 13) of the building due to fire and/or debris-induced structural damage of a critical column (the initiating event) which supported a large-span floor bay with an area of about 2,000 square feet;
>
> *
>
> Vertical progression of the initial local failure occurred up to the east penthouse, and as the large floor bays became unable to redistribute the loads, it brought down the interior structure below the east penthouse; and
>
> *
>
> Triggered by damage due to the vertical failure, horizontal progression of the failure across the lower floors (in the region of floors 5 and 7 that were much thicker and more heavily reinforced than the rest of the floors) resulted in a disproportionate collapse of the entire structure.
>
> ```
>
> This hypothesis may be supported or modified, or new hypotheses may be developed, through the course of the continuing investigation. \*\*NIST also is considering whether hypothetical blast events could have played a role in initiating the collapse. While NIST has found no evidence of a blast or controlled demolition event, NIST would like to determine the magnitude of hypothetical blast scenarios that could have led to the structural failure of one or more critical elements. \*\*
Or, to be more exact -“We didn’t even look for any…oops, was that a mistake?”
Any update on this information yet?
---
### Author:  [@BlakeTyner](https://boards.straightdope.com/u/BlakeTyner)
#### Post date: [July 25, 2010, 5:50pm UTC](https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182/453 "2010-07-25T17:50:43Z")
What’s contradictory about that? If anything, it hints that there needs to be a common understanding about what is meant by “collapse.” What most of us think of as the collapse is what the video and seismic evidence shows–the ‘bulk’ of the building (the floors and perimeter columns) falling to the ground. That occurred in less than 30 seconds.
Now, the whole point of this thread is that the cores of both buildings survived for a period of time after the ‘bulk’ hit the ground–long enough for photos and videos to see the core through the debris/smoke.
But the collapse of the remnants of the core is more like an ‘aftershock’ to the ‘big’ event of the bulk falling. We don’t tend to include the core’s collapse in our general thinking about the towers falling down, because that event was mostly obscured, not as violent, etc.
You can even see it in the videos (such as the one I linked in the OP.) Nobody at the time realized or remarked on the core standing up–because in their minds, the ‘event’ was over.
The common understanding of the collapse, then, is of the ‘bulk’ falling down.
A full understanding of the collapse begins with the sagging floors and pulling inward of the perimeter columns (occurring before the ‘event’ of the bulk collapsing) and ends with the last piece of the interior core hitting the ground–whenever and wherever that happens to be.
---
### Author:  [@Grumman](https://boards.straightdope.com/u/Grumman)
#### Post date: [July 25, 2010, 5:52pm UTC](https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182/454 "2010-07-25T17:52:41Z")
> [@ivan\_astikov](#):
>
> > [@](#):
> >
> > Analysis of the WTC steel for the elements in thermite/thermate would not necessarily have been conclusive. The metal compounds also would have been present in the construction materials making up the WTC towers, and sulfur is present in the gypsum wallboard that was prevalent in the interior partitions.
>
> How convenient.
How bloody obvious to anyone that has a high school understanding of chemistry. In layman’s terms, thermite is made up of a highly reactive metal like aluminium and rust. If you think the presence of aluminium and iron in a skyscraper is suspicious, you really need to put more thought into your attempted gotchas.
---
### Author:  [@ivan\_astikov](https://boards.straightdope.com/u/ivan_astikov)
#### Post date: [July 25, 2010, 5:58pm UTC](https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182/455 "2010-07-25T17:58:41Z")
> [@Grumman](#):
>
> > [@ivan\_astikov](#):
> >
> > > [@](#):
> > >
> > > Analysis of the WTC steel for the elements in thermite/thermate would not necessarily have been conclusive. The metal compounds also would have been present in the construction materials making up the WTC towers, and sulfur is present in the gypsum wallboard that was prevalent in the interior partitions.
> >
> > How convenient.
>
> How bloody obvious to anyone that has a high school understanding of chemistry. In layman’s terms, thermite is made up of a highly reactive metal like aluminium and rust. If you think the presence of aluminium and iron in a skyscraper is suspicious, you really need to put more thought into your attempted gotchas.
But don’t you see that to someone who knew all that, it enables the residue of a thermate device to be hidden in plain sight?
---
### Author:  [@Skywatcher](https://boards.straightdope.com/u/Skywatcher)
#### Post date: [July 25, 2010, 5:59pm UTC](https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182/456 "2010-07-25T17:59:00Z")
> [@Grumman](#):
>
> > [@ivan\_astikov](#):
> >
> > > [@](#):
> > >
> > > Analysis of the WTC steel for the elements in thermite/thermate would not necessarily have been conclusive. The metal compounds also would have been present in the construction materials making up the WTC towers, and sulfur is present in the gypsum wallboard that was prevalent in the interior partitions.
> >
> > How convenient.
>
> How bloody obvious to anyone that has a high school understanding of chemistry. In layman’s terms, thermite is made up of a highly reactive metal like aluminium and rust. If you think the presence of aluminium and iron in a skyscraper is suspicious, you really need to put more thought into your attempted gotchas.
And Steven Jones’ own analysis is missing one key component: barium nitrate.
---
### Author:  [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)
#### Post date: [July 25, 2010, 5:59pm UTC](https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182/457 "2010-07-25T17:59:23Z")
> [@ivan\_astikov](#):
>
> NIST talking bollocks again.
>
> > [@](#):
> >
> > 1. Did the NIST investigation look for evidence of the WTC towers being brought down by controlled demolition? Was the steel tested for explosives or thermite residues? The combination of thermite and sulfur (called thermate) “slices through steel like a hot knife through butter.”
> >
> > NIST did not test for the residue of these compounds in the steel.
> >
> > The responses to questions number 2, 4, 5 and 11 demonstrate why NIST concluded that there were no explosives or controlled demolition involved in the collapses of the WTC towers.
> >
> > Furthermore, a very large quantity of thermite (a mixture of powdered or granular aluminum metal and powdered iron oxide that burns at extremely high temperatures when ignited) or another incendiary compound would have had to be placed on at least the number of columns damaged by the aircraft impact and weakened by the subsequent fires to bring down a tower. Thermite burns slowly relative to explosive materials and can require several minutes in contact with a massive steel section to heat it to a temperature that would result in substantial weakening. Separate from the WTC towers investigation, NIST researchers estimated that at least 0.13 pounds of thermite would be required to heat each pound of a steel section to approximately 700 degrees Celsius (the temperature at which steel weakens substantially). Therefore, while a thermite reaction can cut through large steel columns, many thousands of pounds of thermite would need to have been placed inconspicuously ahead of time, remotely ignited, and somehow held in direct contact with the surface of hundreds of massive structural components to weaken the building. This makes it an unlikely substance for achieving a controlled demolition.
> >
> > Analysis of the WTC steel for the elements in thermite/thermate would not necessarily have been conclusive. The metal compounds also would have been present in the construction materials making up the WTC towers, and sulfur is present in the gypsum wallboard that was prevalent in the interior partitions.
>
> How convenient.
Convenient for reality, yes.
This point of yours is really a copycat of the TWA 800, the guys that did not believe what the evidence told us originally did go to the extreme of stealing evidence, they did test that and found material that \*\*could \*\*had come from a missile…
Alongside material that also had come from mud and sediments close to New York city.
Nope, the most likely explanation remains that the materials came from the contaminated seafloor, I only can see the same result here, like the TWA800 researchers, the researchers of the WTC collapse can not ignore the reality of items that contaminate tests.
---
### Author:  [@Trepa\_Mayfield](https://boards.straightdope.com/u/Trepa_Mayfield)
#### Post date: [July 25, 2010, 6:01pm UTC](https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182/458 "2010-07-25T18:01:00Z")
> [@ivan\_astikov](#):
>
> And even accepting that the airplanes impacts were registered, how equivalent to a placed charge would that amount of energy be? Tell me how big a blip a synchronous explosion with x amount of explosives would create?
It’s funny how all your evidence would look exactly the same as it would if the “OT” was true.
---
### Author:  [@Mr.Miskatonic](https://boards.straightdope.com/u/Mr.Miskatonic)
#### Post date: [July 25, 2010, 6:02pm UTC](https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182/459 "2010-07-25T18:02:42Z")
[quote=“ivan\_astikov, post:451, topic:547182”]
NIST talking bollocks again.
> [@](#):
>
> NIST did not test for the residue of these compounds in the steel.
> How convenient.
Did you read the whole thing? NIST didn’t test for such compound because there was absolutely zero evidence that they were present!
---
### Author:  [@GIGObuster](https://boards.straightdope.com/u/GIGObuster)
#### Post date: [July 25, 2010, 6:04pm UTC](https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182/460 "2010-07-25T18:04:11Z")
> [@ivan\_astikov](#):
>
> Any update on this information yet?
Posted already, but conveniently ignored.
[http://space.crono911.net/EBook/702\_Bazant\_12\_07.pdf](http://space.crono911.net/EBook/702_Bazant_12_07.pdf)
> [@](#):
>
> Several of the parameters of the present mathematical model have a large range of uncertainty.
> However, the solution exhibits small sensitivity to some of them, and the values of others can
> be fixed based on observations or physical analysis. One and the same mathematical model,
> with one and the same set of parameters, is shown capable of matching all of the observations,
> including: (1) the video records of the first few seconds of motion of both towers, (2) the
> seismic records for both towers, (3) the mass and size distributions of the comminuted particles
> of concrete, (4) the energy requirement for the comminution that occurred, (5) the wide spread
> of the fine dust around the tower, (6) the loud booms heard during collapse, (7) the fast
> expansion of dust clouds during collapse, and (8) the dust content of cloud implied by its size.
> **At the same time, the alternative allegations of some kind of controlled demolition are shown to
> be totally out of range of the present mathematical model, even if the full range of parameter
> uncertainties is considered. These conclusions show the allegations of controlled demolition to
> be absurd and leave no doubt that the towers failed due to gravity-driven progressive collapse
> triggered by the effects of fire.**
[Previous page](https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182.md?page=22)
[Next page](https://boards.straightdope.com/t/an-angle-of-the-wtc-collapse-id-never-seen/547182.md?page=24)