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Comment by 3pt14159 | Hacker News Reader

I studied structural engineering. The 2008 NIST report changed my view. Beforehand I thought the 9/11 A&E for Truth movement may have had some valid points. I suspected it was due to poor construction inspection or possibly corruption but I didn't rule out conspiracy completely. But when I read the report and it explained the mechanisms for failure I was completely convinced. Heat expanded the beams which pushed the exterior columns out of plane which, in conjunction with the heat, caused their failure. I don't know a single engineer that has read the report that disagrees with its findings.

All of this to say, there are plenty of engineers that may have signed on to the original pledge that may have read the report and changed their minds. I never signed it, but I don't recommend buying into their claims. We have reasonable answers now.

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I expect I'll get thoroughly thrashed and branded an idiot for daring to ask, but since you studied structural engineering, I really want to take the opportunity.

Is your comment exclusively for the two main towers, or tower 7? I have spoken with engineers who have reluctantly expressed confusion over tower 7. I'd appreciate a reply if you can bear it.

To others: I know to even touch the subject will have many sharpening their axes. Please save them for something other than honest curiosity, if you can.

Confusion is likely as far as we're ever going to get with tower 7. Not because there was a grand conspiracy in play, but because we lack information about what happened in tower 7, period. That's generally what people who disbelieve the official consensus misunderstand... Absence of evidence is not evidence of conspiracy.

The Alaska conclusions are correct as per their model. But their model is making assumptions about the spread of the fire and the damage that we lack concrete information to confirm or deny. It's easy to forget that on the day WTC 7 fell, we don't know how much of that building was on fire. A significant percentage of New York first responders had just died... There wasn't enough fire management on scene at WTC 7 to gather reasonable amounts of information, much less fight the fire.

It might have fallen due to thermal expansion of the main structural elements. It might have fallen due to controlled demolition. It might have fallen due to a sudden upsurge of the mole people from Hollow Earth. Too few people had eyes on for us to ever really know.

(Personal opinion: I don't know that we have any good models of what happens to a building close to but under 50 stories when two of the tallest buildings on the planet collapse immediately next to it. What earthquake-magnitude-equivalent force did the foundation of WTC 7 experience, and what effect would that have? The mole people model might be more accurate than I want it to be. ;) ).

Yes, my comment is only in regards to the two main towers. I didn't study tower 7 in detail, but from what I understand it was a building that had an interior backup generator with enough fuel for a week or two and that is what caused the large fire. But when the 9/11 truth movement was in its prime, most of the focus was on towers 1 & 2 and once I was satisfied with the explanations for those I didn't bother looking into the secondary claims about tower 7. Mostly because once you have the first two towers collapse all the heat and debris from the pyroclastic cloud it makes doing the math much harder. The heat calculations for the two planes were relatively straightforward, other than the degree of fireproofing displacement during impact.

> I don't know a single engineer that has read the report that disagrees with its findings.

Just want to point out that the document that OP linked claims in the conclusion that the NIST report is invalid, but I have no ability to judge that claim. I have no structural engineering knowledge and have never heard of either of these reports until now.

This was published March 2020 though, and I'd be curious if the analysis was cogent enough to warrant NIST's response in a few years

I thought the “jet fuel can’t melt steel beans” guys were way off base from day 1. You don’t have to get steel fully melted to weaken it. Anybody who has messed around with a blowtorch and a section of rebar knows this. Plus the building had just been hit by a fully loaded jumbo jet and several of the supports were damaged in the impact.

The idea that someone snuck in hundreds of explosives and attached them to the building without any of the thousands of people who work in it noticing as a backup to an already elaborate air hijacking plan makes no sense.

What does make sense is that in an attention economy it is pretty easy to grab people’s attention by taking a significant event and trying to convince people that the common narrative is false is very profitable. You get a lot of attention and if you do a good job the idea grows all on its own and becomes something you can capitalize on the attention for a long long time.

What I don't understand is what value do people get out of promoting this type of conspiracy theory? Who profits? Is it just attention seeking or is there some profit motive? If so what?

I'm all for exposing corruption and I think there is enough to keep any anti government person occupied, but why do we get people inventing conspiracies in the most improbable of places? 9/11, Covid19 etc.

Thinking you've found a hidden truth is unreasonably fun. And then you can form a community and have some fun with your fellow nutbars too.

People also want the world to make more sense than it actually does. There being a secret group running things is at least _an_ explanation for the weird shit that happens, even if it doesn't really hold together.

There's a bunch of profit motives and politics involved as well usually.

If your goal is to erode trust in institutions then pushing any and all conspiracy theories is worth your time. Anywhere you see people trying to undermine the local government you see conspiracy theories.

Conspiracy theories are great because they're so efficient. Once started they are self reinforcing.

Presumably, those “Loose Change” frat guys made some money off it…

> What I don't understand is what value do people get out of promoting this type of conspiracy theory? Who profits? Is it just attention seeking or is there some profit motive? If so what?

They must really believe that what they're saying is true.

One interesting point some "truthers" make is that the welded steel lattice frame of the buildings should have been an efficient heat sink transfering heat away from hotter areas to colder areas. So warpage is unlikely to have been significant. On the other hand thermal expansion of relatively straight beams is likely what brought the towers down.

But you do have to get steel melted to have molten steel.

What heat was there which affected building 7?

WTC 7 was on fire for about 5 hours, with about 7 or 8 floors on fire as a result of WTC 1/2 debris crashing into the building and starting fires. It wasn't helped by the water mains failing due to the collapse of WTC 1/2, which meant the sprinklers failed in the lower portion of the building.

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