Naked Science Forum
On the Lighter Side => New Theories => Topic started by: L_D on 19/04/2010 04:43:14
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This is a question relating to the third highrise that fell on 9/11, WTC 7 otherwise known as building 7, if any reader has not seen the collapse of this third building then please have a look at this very short video:
Freefall occurs early in the very symmetrical collapse of WTC 7 for 2.25s or approx 8 stories, it was first accurately measured by a physics teacher (David Chandler) who challenged NIST about freefall when they accepted comments on the draft copy of the final report.
When challenged, NIST denied freefall occurred and said that freefall could only occur to the building if there were no structural components components below it(1), but then in the NIST final report there was an admission of freefall for 2.25s(2) but no explanation accompanying the change.
If freefall means that all the buildings potential energy is being used to accelerate the building downwards, then what energy source did the significant work of removing the 80+ steel columns?? Can freefall occur if the falling building is also doing the 'work' of overcoming the 80+ steel columns??
In controlled demolitions precisions placed and precision timed explosives are used to near simultaneously remove all the structural elements, once the columns are removed freefall is possible.
Most people intuitively recognise the symmetrical collapse of WTC 7 through the path of most resistance as a controlled demolition, does freefall prove controlled demolition on 9/11???
(1)
(2)"Stage 2 (1.75 to 4.0 seconds): gravitational acceleration (free fall)"
http://www.nist.gov/public_affairs/factsheet/wtc_qa_082108.html
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The first link you gave has NIST's explanation:
In a video, it appears that WTC 7 is descending in free fall, something that would not occur in the structural collapse that you describe. How can you ignore basic laws of physics?
In the draft WTC 7 report (released Aug. 21, 2008; available at http://wtc.nist.gov/media/NIST_NCSTAR_1A_for_public_comment.pdf), NIST stated that the north face of the building descended 18 stories (the portion of the collapse visible in the video) in 5.4 seconds, based on video analysis of the building collapse. This time period is 40 percent longer than the 3.9 seconds this process would have taken if the north face of the building had descended solely under free fall conditions. During the public comment period on the draft report, NIST was asked to confirm this time difference and define the reasons for it in greater detail.
To further clarify the descent of the north face, NIST recorded the downward displacement of a point near the center of the roofline from first movement until the north face was no longer visible in the video. Numerical analyses were conducted to calculate the velocity and acceleration of the roofline point from the time-dependent displacement data. The instant at which vertical motion of the roofline first occurred was determined by tracking the numerical value of the brightness of a pixel (a single element in the video image) at the roofline. This pixel became brighter as the roofline began to descend because the color of the pixel started to change from that of the building façade to the lighter color of the sky.
The approach taken by NIST is summarized in Section 3.6 of the final summary report, NCSTAR 1A (released Nov. 20, 2008; available at http://wtc.nist.gov/NCSTAR1/PDF/NCSTAR%201A.pdf) and detailed in Section 12.5.3 of NIST NCSTAR 1-9 (available at http://wtc.nist.gov/NCSTAR1/PDF/NCSTAR%201-9%20Vol%202.pdf).
The analyses of the video (both the estimation of the instant the roofline began to descend and the calculated velocity and acceleration of a point on the roofline) revealed three distinct stages characterizing the 5.4 seconds of collapse:
* Stage 1 (0 to 1.75 seconds): acceleration less than that of gravity (i.e., slower than free fall).
* Stage 2 (1.75 to 4.0 seconds): gravitational acceleration (free fall)
* Stage 3 (4.0 to 5.4 seconds): decreased acceleration, again less than that of gravity
This analysis showed that the 40 percent longer descent time—compared to the 3.9 second free fall time—was due primarily to Stage 1, which corresponded to the buckling of the exterior columns in the lower stories of the north face. During Stage 2, the north face descended essentially in free fall, indicating negligible support from the structure below. This is consistent with the structural analysis model which showed the exterior columns buckling and losing their capacity to support the loads from the structure above. In Stage 3, the acceleration decreased as the upper portion of the north face encountered increased resistance from the collapsed structure and the debris pile below.
Conspiracy theorists won't accept this, of course, but it doesn't seem to be violating the laws of physics or to require controlled demolition.
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I have to ask What JP, Hero Member means that "conspiracy theories refuse to accept this"?
The question is in the title, and NIST even previously stated freefall acceleration to be impossible (assuming they mean in significant duration, as in multiple stories) without some assistance in removing the support structure beneath the collapse in order to avoid deceleration that would be necessary due to the energy absorption of the supports being collapsed.
He then posts an NIST explanation that doesn't answer this question and states "CT's" refuse to accept their answer, accept they only raise more questions by stating that indeed they were wrong in their previous statement that no freefall occurred in WTC7, and they infact find it did occur for about 8 stories. Did they claim in there somewhere that I'm missing that buildings can freefall collapse?
How is it possible for the building to have experienced freefall for an entire 8 stories? (I do know that controlled demolitions do not experience freefall for the entire duration, generally increasing acceleration, freefall (or even sometimes just near freefall), then slowing again as the rubble pile builds)
I can't find a scientific explanation short of the collapse having been assisted by some energetic removing supports beneath the collapse.
['Revived' topic merged with original - Mod]
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I have to ask What JP, Hero Member means that "conspiracy theories refuse to accept this"?
What he said was "Conspiracy theorists won't accept this"
I believe he meant that those who believe in conspiracy theories (like, for example, that the WTC was demolished by explosive charges) will never be persuaded otherwise.
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To answer your question about the free fall for 8 stories, that is explained in the NIST report.
In stage 1, the structure fell much slower than free-fall, due to the buckling of the supports. At the end of stage 1, the supports failed, so that during stage 2, they provided no support and the building collapsed in free fall. In stage 3, the building had collapsed enough that the debris piling up below it caused it to slow down again. This was all checked by simulations run by NIST.
What I meant about conspiracy theorists being unwilling to accept these answers is just that. If they could offer good, scientific refutation of the simulations run by NIST that would be one thing. From what I've seen and heard on the subject, the opposing arguments don't use facts. They just involve proof by loud assertion that "buildings can't fall in free fall ever!"
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Ok...
I watched all 3 videos.
As far as I could tell, one big issue was the start and end time in the analysis. David Chandler seemed to only look at the video until the center of the building was obscured, while NIST apparently continued until none of the building was visible. See discussion around minute 2:22 on second video. A large portion of the building to the right is still clearly visible after David Chandler stopped his measuring.
There may have been a period near the start of the collapse where the acceleration was high, approaching 1G. However, the rest of the collapse appeared to fall at constant velocity (nearly zero acceleration).
Sorry, I have no demolition experience. I do find it interesting that the roof comes down nearly evenly, parallel to the ground, except for the center section that comes crashing down first (and may even completely disappear from view).
Many of these skyscrapers depend on a central columnar support (perhaps around the so-called penthouse). If that central column buckled, then it might take the rest of the building down pretty much stepwise as apparently happened.
As far as what happened to the concrete and steel...
These are huge, massive buildings. I'm showing:
200,000 tons of steel
425,000 cubic yards of concrete.
12,000 miles of power lines.
Anybody volunteer to store that in their backyard?
At 1¢ to 4¢ per pound, for scrap steel... that is $20 to $80 per ton. That gives somewhere between $4 Million and $16 Million in scrap steel. I suppose just a drop in the bucket when compared to the entire value of the buildings and cleanup, but should the government seize it?
I'm sorry about the conspiracy theories... I could imagine that someone had some kind of a premonition that something was about to happen, even non-specific. But I can't imagine any active government participation.
Now, the World Trade Center had been unsuccessfully bombed in 1993. Any terrorists attacking it in 2001 would have been aware of the previous attempt. It is hard to imagine a mechanism for them to have smuggled bombs into the structures in 2001, but it would not have been unimaginable that they would have not only planned an air attack, but complimented it with a ground attack. However, the apparent non specific nature of the impact points on the WTC towers would have made it difficult for them to have planted explosives on the specific floors involved.
Here is a good video about the main tower collapse.
Building 7 likely involved somewhat different mechanisms.
I read that the US Government dropped flyers prior to bombing Hiroshima claiming that an attack was imminent on 1 of 30 possible cities. Very humanitarian... but what were the Japanese supposed to do? Abandon all 30 cities? Likewise, even if someone had leaked information about a non-specific terrorist plot... should we have shut down the entire country?
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I'm still finding a hard time accepting that this actually has happened. And it disturbs me that we still solve disputes by force.
And reading you Clifford about the A-bombs it reminds me of the 'fuel-bombs' used in Iraq, I think it was? They are the next thing to an atomic explosion in that they cover a very large area as a vapor/fog before staring to 'burn'. The first time the allied warned the Iraqis didn't care as they had no notion of what that bomb was. The second time they ran away, although some got shot by their own for 'desertion'?
It reminds me of the first world war, when there was an British order not to let fliers use/have parachutes, 'As that might make them want to 'bail out' to fast from a fight.'
Idiots exist in all times it seems..
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Ok...
I watched all 3 videos.
These three, right?
(that's part I)
Sorry, my current location isn't cooperating with all the links.
As far as I could tell, one big issue was the start and end time in the analysis. David Chandler seemed to only look at the video until the center of the building was obscured, while NIST apparently continued until none of the building was visible.
In NIST's report they claimed that the time the building took to fall for the first ~17 stories (the portion you refer to) was 40% longer than it would have taken in freefall, and that is what's being addressed. Please pay closer attention, as that was quite clear in the video (though David refers to it as 18 stories worth).
NIST says ~17 floors = 3.9 seconds if they were in freefall but 'their model' showed it took 5.4 seconds. They blatantly avoid any mention of actual analysis and mention this is the result from their model, at first.
See discussion around minute 2:22 on second video. A large portion of the building to the right is still clearly visible after David Chandler stopped his measuring.
Again, so did NIST, at least in the aspects of the argument in the videos, "till it disappeared from view between the two buildings seen in the video".
Then they offer the average speed in rebuttal to an acceleration question, an average speed with an additional 1.5 seconds completely fabricated to match their model's number.
There may have been a period near the start of the collapse where the acceleration was high, approaching 1G. However, the rest of the collapse appeared to fall at constant velocity (nearly zero acceleration).
Are you just making things up as a rebuttal? Neither NIST nor David made such a claim, why do you? Their data shows acceleration. It's the rate of acceleration that is in question.
Sorry, I have no demolition experience. I do find it interesting that the roof comes down nearly evenly, parallel to the ground, except for the center section that comes crashing down first (and may even completely disappear from view).
Naturally occurring symmetrical collapse from asymmetrical damage in such a well built building would definitely yield some new theories in engineering and physics.
Many of these skyscrapers depend on a central columnar support (perhaps around the so-called penthouse). If that central column buckled, then it might take the rest of the building down pretty much stepwise as apparently happened.
And do you realize that a collapse of that portion of the structure would lose significant amounts of kenetic energy in order to move the intact, sturdy portions surrounding it?
As far as what happened to the concrete and steel...
These are huge, massive buildings. I'm showing:
200,000 tons of steel
425,000 cubic yards of concrete.
12,000 miles of power lines.
Anybody volunteer to store that in their backyard?
How about a chunk of land designated to holding the evidence one of the greatest crimes this nation has every incurred?
At 1¢ to 4¢ per pound, for scrap steel... that is $20 to $80 per ton. That gives somewhere between $4 Million and $16 Million in scrap steel. I suppose just a drop in the bucket when compared to the entire value of the buildings and cleanup, but should the government seize it?
Money should not usurp justice, but many would disagree with me here and take your stance that the money matters more.
The rest of your post has nothing to do with the topic if we are to remain focused, and that is what I wish. It's mostly fallacy and assumptions that can't be made without actually delving into study on the matter.
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How about a chunk of land designated to holding the evidence one of the greatest crimes this nation has every incurred?
This is a science forum. It's not a conspiracy theory forum.
I'm locking this thread.