15 Years Later: on the physics of high-rise building collapses [pdf] | Hacker News Reader

15 Years Later: on the physics of high-rise building collapses [pdf]

europhysicsnews.org

17 points2a0c4029 comments

There are several half-formed complaints from people who did not read the article in this comment thread. I'm guessing that the commenters are having a knee-jerk reaction to the fact that there are a lot of conspiracy theorists out there who think that the US government did 9/11 etc.

This article is not about that. It revisits a disaster (the collapse of WTC7) which appears to have happened under very unique circumstances. If the accepted explanation is correct, WTC7 is the only high rise to ever have collapsed from fire, and the collapse resulted from a long string of coincidences. The article is a critique of this analysis.

>...and the collapse resulted from a long string of coincidences.

-Most, if not all spectacular, unexpected events are the result of a long string of coincidences. Otherwise, they'd be common occurrences.

That would work with one building. A long string of coincidences (failures upon failures…), such as the ones that causes some big server outage, or blackout, or plane crash, could have been a good explanation for the fall of one building.

Here however the "string of coincidences" hypothesis would have to apply pretty much simultaneously to three buildings, one of which wasn't even hit by a plane.

No. freaking. way. That's just too damn improbable.

You're ignoring correlation. The twin towers are, for almost all purposes, virtually identical, and experienced largely identical scenarios. For them to behave differently under such circumstances would be less extraordinary than for them to behave similarly.

To my knowledge, the twin towers are the only buildings in history to have been hit with a four-engine plane full of fuel (El Al Flight 1862 apparently had only two engines left when it struck the apartment building. Note that the building fully collapsed at point of impact). Again, to my knowledge, with WTC 7, they were the only high-rises to have experienced serious, out of control multi-floor fires for hours after receiving major structural damage--Deutsche Bank received serious damage but no fires so far as I can tell.

If 100% of similar structures in similar circumstances have failed in a similar manner, is that improbable?

Then we're veering off the "multiple coincidences" hypothesis, to a much more probable theory.

These coincidents can usually be explained by a latter analysis. That's the main point of the article: til now there is no logically sound string of events that explains the observed events, demolition, fire or otherwise. These events might indeed be of low probability but currently even the events are not known.

People are calling this a truther article. It's not surprising when it's written by people like this:

    Ted Walter is the director of strategy
    and development for Architects & Engineers
    for 9/11 Truth (AE911Truth),
    a nonprofit organization that today
    represents more than 2,500 architects
    and engineers. In 2015, he authored AE-
    911Truth’s Beyond Misinformation: What Science Says
    About the Destruction of World Trade Center Buildings 1,
    2, and 7. He holds a Master of Public Policy degree from
    the University of California, Berkeley.

The article is full of truther bullshit. You've said, twice, that this article is about WT7. The article is full of detail on the twin towers as well as WT7.

Unless you state what is wrong and what is correct. This has no meaning.

> This article is not about that. It revisits a disaster (the collapse of WTC7) which appears to have happened under very unique circumstances. If the accepted explanation is correct, WTC7 is the only high rise to ever have collapsed from fire, and the collapse resulted from a long string of coincidences. The article is a critique of this analysis.

A critique that suffers from the same flaw it's criticizing. The authors say (pg. 4, there, I'm showing I actually read the article) that the official study preconcluded the cause of collapse even though it can't make the evidence fit, but the authors of this article themselves are equally guilty of such preconclusion (it was controlled demolition!).

Some of the citations are extremely problematic--the evidence for nano-thermite in particular, which is not a claim that can be independently backed up, and whose properties are never clearly specified (because, so far as I can discover, the known properties really fail to explain any aspect of 9/11).

I find the conspiracy theories surrounding 9/11 somewhat amusing.

With regards to controlled demolition - how on earth would anyone be able to rig the buildings for controlled demolition without anybody noticing?

And why use slow-acting thermite when shaped charges would be more efficient and harder to detect (both before, during and after the event)

Not to mention - how have They(tm) been able to keep their conspiracy under wraps?

Seriously - you pull off a massive gig like this, hardly the work of a couple of lone wolves - and no-one talks?

It's best not to think about it. Conspiracy theorists have a tendency to take confirmation bias to an extreme. If you provide a counter argument, they don't respond to that argument, they attack your character by "realizing" that you're part of the conspiracy too.

Isn't calling them "conspiracy theorists" itself an attach on their character?

Personally, I like to play devils advocate, and I'm curious about what happened on 9/11. It doesn't add up for me. So I have taken the "conspiracy theorist" side several times... I don't see people making arguments against the theorists data.

I see the same common fallacies, most often variations of appeal to authority. "Popular science debunked that" for example in response to an argument that Popular Science didn't address.

"If it were a cover up it would have gotten out" in response to people pointing "it getting out" is my favorite, of course. Sort of a "I don't believe it, therefore it can't be right". Not sure what fallacy that is.

> Isn't calling them "conspiracy theorists" itself an attach on their character?

I've never thought of it like that. For me, I've always looked at it as a literal definition. They theorize that there is a conspiracy. However, I guess it could be seen as an attempt on someone's character because it does have a negative connotation.

Ok, so you asked a series of questions and I presume you don't know the answers so I want to tell you the positions I've heard people take in response to them, but I am afraid I am going to be downvoted heavily. So, before you downvote me, realize I'm answering questions that are asked right here. Or is this just a troll setup to get someone to stick his head up to be beat up? Is this a form of smear the queer? I would hope HN hasn't sunk that low.

Rigging the building- there was a large amount of short term, sudden work done on the interiors of the buildings in the weeks before 9/11. This was done at night, some claims about "asbestos checking" or other reasons were given. Multiple reports form workers in the buildings about this happening, with large work crews in there. (I am relating the reports I have heard, and thus what I believe people believe- the answers to the question- I'm not stating this happened as an objective fact, I cannot prove it. I am not taking a position on its veracity or most of the explanations I give below. I'm merely relating the beliefs of other people.)

It of course seems mighty coincidental that there was this asbestos remediation work and inspections going on in these buildings right before the attack. There are a lot of such coincidences, such as the unusual insurance situation with the twin towers right before, the head of security of the twin towers being related to the administration, the fact that there was a "scenario" being "war-gamed" on that very day (allegedly) that involved jetliners hitting towers-- and then it actually happens?! To be honest that just seems like sloppy work.

Also, in a controlled demolition situation there is a characteristic sound of the many charges going off. This sound has been reported by many witnesses on 9/11. Of course they are all just people- office workers and the like, but even some firemen- so they aren't "authorities". But multiple explosions before the collapse are a common eye witness claim.

Slow acting thermite vs shaped charges- I don't know what the common theory is, but I've seen arguments that shaped charges were used, particularly based on the cuttings in some of the beams in wreckage that was exposed. I'm under the impression that most who believe the controlled demolition theory believe that it was shaped charges. I'm not sure how or why thermite would be involved.

How to keep the conspiracy theory under wraps? That's the easiest part.

Ever watch the show "Penn & Teller: Fool Us"? Particularly if you binge watch the show it's kinda amazing how every trick fools you and you have to take a few minutes figuring it out. Sometimes you can figure it out easily, sometimes you're stumped. But the ones that stump you, if you go online and find out how they are done are obvious in retrospect.

The unfortunate reality is that we are not as objective as we would like to believe. What we believe is in large part based on what we want to believe. We want to believe our eyes so when the girl magically appears behind the sheet on stage we want to believe it is magic, and most people just go never knowing how it is done. On some level they know, but they don't look deeper.

Misdirection is very powerful. People are not in the habit of looking for it, and its easy to knock down online as "paranoia" when it is pointed out.

Further we are raised from kindergarten to believe in the government, that the government is benevolent and that we can trust our rulers. It's hard to overcome that and be objective. You know in North Korea they feel the same way. In Japan during WWII many people sacrificed themselves because they loved their Emperor. People worship dictators, its' easy to believe they will give more than the benefit of the doubt to a democratically (in theory, 2000 is another bit event) elected president.

The very week of 9/11 people were talking about how those buildings wouldn't fall naturally like that, and what we've had since then is 15 years of an Official Conspiracy Theory (the al queda box cutter theory) propagandized far and wide and any alternate theories, or even people asking questions shot down as "conspiracy theory's" or elsewhere here in this thread "truth bullshit".

Personally I don't know what happened. I don't believe things went down as they are claimed exactly- I'm incredulous that the entire air force stood down for a day when just a year earlier they were on a rogue lear jet in 15 minutes after loosing contact with it.

But the most telling thing is the term "Al Queda". Al Queda was, we were told in the late 1990s "the CIAs code name for the mujahideen fighters they supported in the afghani war in the late 1980s". But somewhere after 911 "Al Queda" became not a code name to describe a group of unorganized people, but a sinister organization with "cells" everywhere.

This means that Bin Laden somehow-- and here I'm imagining Tom Cruise getting the NOC list in the first Mission Impossible, only with a robe and a long assed beard hitting the floor-- snuck into the CIA and found this top secret code name "al queda" and then decided to name his massive organization by that name?

You're right, you can't keep this massive conspiracy under wraps. You can't make a woman appear out of thin air.

It doesn't matter.

Most people won't believe it.

Germans for years couldn't accept that the Holocaust had happened, and right under their noses. After all they arent[ monsters.

Many still don't want to believe it.

I don't know what happened, but it's not like the Official Conspiracy Theory is an open and shut case.

> Also, in a controlled demolition situation there is a characteristic sound of the many charges going off. This sound has been reported by many witnesses on 9/11. Of course they are all just people- office workers and the like, but even some firemen- so they aren't "authorities". But multiple explosions before the collapse are a common eye witness claim.

I happened to be able to observe a controlled demolition building across the street from my dorm room in undergrad. There's a distinctive set of sounds. Before the demolition starts, there was months of preparatory work, including concrete saws to cut out holes in the walls (those were particularly loud and noticeable from over a block away). The actual demolition had a few different kinds of charges going off, starting with a machine-gun-like rapid fire, followed by a few massive explosions in regular sequence.

If 9/11 were controlled demolition, it would be unlike any other controlled demolition I've heard of--a few sporadic explosions is not indicative of controlled demolition.

> I'm not sure how or why thermite would be involved.

The mysterious molten metal. Many conspiracy theorists hold that it's molten steel, and they invoke thermite to explain how to melt steel.

> I'm incredulous that the entire air force stood down for a day when just a year earlier they were on a rogue lear jet in 15 minutes after loosing contact with it.

KAL 007 was a civilian airliner that mistakenly flew over restricted Soviet airspace during a high-tension period of the Cold War. It took the Soviets about 2.5 hours to scramble a plane to shoot it down.

The flight you mention (see https://en.wikipedia.org/wiki/1999_South_Dakota_Learjet_cras...) appears to have gone 1.5 hours between loss of contact and first interception. This should also be countered with the fact that the transponder was on the entire time, and that intercepting planes were borrowed from wings already in the air. There was never any uncertainty about where the plane was, unlike a plan that turns off its transponder right before turning around 180°.

Intercepting the hijacked planes would have had to have been done within about 30-45 minutes of hijacking--requiring the FAA to notify the military of the hijacking, the military to scramble planes, search for the (transponder-less) aircraft among the other airplanes in the air (busy airspace!), and shoot it. If you think that's easy, go to <https://www.flightradar24.com/40.91,-76.43/7> and tell me how long it would take you to figure out which one of those planes was hijacked.

> Germans for years couldn't accept that the Holocaust had happened, and right under their noses. After all they arent[ monsters.

I recently read a book (The German War) which covered WWII from the perspectives of ordinary Germans. There was no delusion: everyone knew that the Holocaust was going on, but no one wanted to talk about it. The prelude to the total extermination of the Jews was the killing of mentally disabled, etc., populations, which was carried out with more secrecy (possible because it was much smaller scale), and met with some resistance by religious leaders--who decided not to repeat the ordeal when the much larger Holocaust actually went on.

If you want to believe that the towers were brought down by controlled demolition on the orders of the US government, then answer this: why is there nothing on Wikileaks about it?

It doesn't talk much about the damage from impact and also jet fuel.

This is about WTC7, which was not hit by a jet, and did not come into contact with jet fuel. It's the only skyscraper ever to have collapsed from fire.

... after getting a front-row seat to two massive buildings collapsing. There was some serious damage to the building from the collapse of the towers, which was after all responsible for starting many of the fires.

Also, as far as I'm aware, almost all skyscrapers with major fire damage are largely uncontrolled fires on one or two floors, rather than uncontrolled fires throughout the entire building.

Also: http://www.sfgate.com/bayarea/article/Tanker-fire-destroys-p... --that's a steel structure (overpass, not a skyscraper) being collapsed entirely due to an out-of-control fire (due to a crashed gasoline truck).

I know paper burns at fahrenheit 451 (thanks Ray Bradburry)... what temperature does jet fuel burn at? Or that gasoline truck? I presume it's a much higher temperature.

The jet fuel that hit the twin towers was mostly expelled in massive fireballs, with some of it draining into the towers.

I don't see a reason to believe WTC 7 was saturated in jet fuel. So WTC 7 was a paper & wood and fabric fire, right?

> Meanwhile, unreacted nano-thermitic material has since been discovered in multiple independent WTC dust samples [13]

http://www.911research.wtc7.net/mirrors/bentham_open/ActiveT...

Suspicious Indeed.

FYI: Truther article

Yeah, with lots of weasel words and written by people who are not qualified on the topic.

It's written by a professor of physics, a professor of civil engineering and a mechanical engineer.

The physicist in the group should be classified as a particle physicist, not a structural mechanics expert. That's as worlds different as saying that someone who studies compiler research is qualified to talk about recurrent neural networks.

This needs to be tagged as such, I started reading this believing that it was a reputable paper.

Is an article that comes to a conclusion different than the one you believe automatically false? That seems to be your only complaint.

Conspiracy theorists (in general) have been known to make stuff up, and non-experts who believe in them can easily parrot this stuff thinking it's true. A great example of this in history is the "Magic Bullet Theory" of JFK's assassination, which holds that the single bullet is false because the bullet would have had to make sharp turns to get to its next target, which is almost entirely based on made-up positions in a fake film.

Thus, for an article which is espousing that the towers came down only via controlled demolition, it is necessary to find independent sources of all facts mentioned, even ones as pedestrian as the expected weight of a floor of a building. (I haven't done the math myself, so I hold no opinion as to whether or not the numbers in the article are correct).

Your characterization of the Magic Bullet Theory is inaccurate. The error is in not realizing the car was of an unusual geometry (I believe JFK was elevated, and the seats were different widths apart between the front and the back- unusual for cars of the time.) So assuming the car was normal, and all the seats were the same distance apart and the same height, you would need a magic bullet. Applying deeper understanding of the setup of the car accounts for that, reducing it to the improbable bullet theory. That doesn't mean they were wrong, that means they didn't have access to the car to do direct measurements. When the government locks down the evidence (or in the case of 9/11 immediately ships it off to china, before the investigation begins, literally shipping buildings across the ocean to be recycled) it's not the fault of the conspiracy theorists if they come up with wrong hypothesizes when denied access to the evidence every legitimate researcher should have access to.

Regarding "fake film" you seem too be referring to Oliver Stones "JFK" which is not the source of the Magic Bullet Theory, or any of the theories there, it is merely a collection of the theories prominent at the time, and then fictionalized.

Yes. "Truther" is code word, like "birther" and "denier" and "conspiracy theorist". It basically means "anyone who doesn't agree with the Official Positions Of The Ministry of Truth, and is thus ipso facto without credibility".

It's from a very anti-intellectual ideology.

Literally these people reject the scientific method. They are rejecting argument evidence and claims based on the source, not based on the quality of the arguments (which is talking to the person not the point, and a form of fallacy of appeal to authority)

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