Collapse Theory Fails Reality Check

[tenseconds]

Observations from 9/11 by Nila Sagadevan

On page 305 of the 9/11 Commission Report, we are told, in the government's "complete and final report" of 9/11, that the South Tower collapsed in 10 seconds. (That's the government's official number. Videos confirm that it fell unnaturally, if not precisely that, fast. See for yourself: QT Real)

But as we've just determined, that's free-fall time. That's close to the free-fall time in a vacuum, and an exceptionally rapid free-fall time through air.

But the "collapse" proceeded "through" the lower floors of the tower. Those undamaged floors below the impact zone would have offered resistance that is thousands of times greater than air. Recall that those lower floors had successfully supported the mass of the tower for 30 years.

Air can't do that.

Can anyone possibly imagine the undamaged lower floors getting out of the way of the upper floors as gracefully and relatively frictionlessly as air would? Can anyone possibly imagine the undamaged lower floors slowing the fall of the upper floors less than would, say, a parachute?

It is beyond the scope of the simple, but uncontested, physics in this presentation to tell you how long the collapse should have taken. Would it have taken minutes? Hours? Days? Forever?

Perhaps. But what is certain, beyond any shadow of a doubt, is that the towers could not have collapsed gravitationally, through intact lower floors, as rapidly as was observed on 9/11.

Not even close!

Because, as you may recall, not only was much energy expended in causing the observed massive high-speed sideways ejections, but virtually all the glass and concrete was "pulverized" -- actually "dissociated" is a much better word. (Nevermind what happened to all the supporting steel core columns...!!!) And the energy requirements to do anything even remotely like that rival the total amount of potential energy that the entire tower had to give. (source) So while gravity is nearly strong enough to cause some things to fall that far, through air, in the observed interval, and while gravity is probably not strong enough to have so thoroughly disintegrated the towers under their own weight, gravity is certainly not strong enough to have done both at once.


Conclusions

In order for the tower to have collapsed "gravitationally", as we've been told over and over again, in the observed duration, one or more of the following zany-sounding conditions must have been met:

The undamaged floors below the impact zone offered zero resistance to the collapse
The glass and concrete spontaneously disintegrated without any expenditure of energy
On 9/11, gravity was much stronger than gravity
On 9/11, energy was not conserved
However, none of these physics-violating conditions can be accounted for by the official government conspiracy theory of 9/11, nor by any of the subsequent analyses designed to prop up the official theory of 9/11.

Bottom line: the government/PBS/PM/SA explanation for the WTC collapses fails the most basic conservation-of-energy reality check. Therefore the government/PBS/PM/SA theory does not fit the observed facts; the notion of a "pancake collapse" cannot account for what happened. The "pancake collapse theory" explanation is impossible, and thus absurd.

It is utterly impossible for a "gravitational collapse" to proceed so destructively through a path of such great resistance in anywhere near free-fall times. This fact debunks the preposterous contention that the observed WTC collapses can be blamed solely upon damages resulting from aerial assaults.

So, to the extent that people accept the ridiculous "pancake collapse" explanation, Gates' other premise, that people know what they saw, is also incorrect. It is left to the reader to decide if his conclusion, which was based upon two incorrect presumptions, is also flawed.

The purported "gravitational" collapse (video) of World Trade Center building 7, which was hit by zero aircraft, and which also vertically collapsed in within a second of free-fall-time-in-a-vacuum later that same day, similarly fails this same conservation-of-energy analysis.

The explanation for how and why so many highly-accredited and credentialed people all so miserably failed to check the "pancake collapse" theory, by giving it this basic reality check, is beyond the scope of this simple physics discussion.

read entire article with gravity physics equations proof http://www.911blimp.net/prf_FreeFallPhysics.shtml

If dropped at the same time, which would reach the ground first?


If dropped at the same time, which would reach the ground first?

[DoYouEverWonder]

1. But all the OCters claim

that despite the visual evidence, the buildings did not collapse in free-fall time. Even though the NIST report confirms the actual times for the collapses and admits that they come down ssentially in free fall.

[whistle]

107. Denial is not a river in Egypt....

...DeNile is.

[Nozebro]

124. Better to pay attention to what TRUTH Seekers say or claim. It's not

realistic to expect OCT'ers to be any help in finding the truth about anything which could mean the OCT Fairy Tale is just that.

[vincent_vega_lives]

147. If not exactly 9.8 meters per second/

per second, then it is not free fall. 9.2 seconds is the time it would take the roof to reach the sidewalk at free fall acceleration.

Did the roof EVER reach the sidewalk? I doubt it. How high was the debris pile? At the point the building ceased collapsing, it was some 40m shy of the sidewalk.

376m = (.05)*(t m/s/s)*(9.2*9.2)

That would be more like 8.9 m/s/s...NEAR free fall, would be more accurate.

[tabatha]

2. a comment I made in an email in July...

The concrete slab pancake theory fails on two points
1) the concrete could only be in one of two places - acting as solid forceful pancakes causing the collapse
or as pulverized concrete as seen on TV. Well, as facts and video demonstrate, the concrete slabs were being pulverized (by explosives).
2) .....

but stated better in the article:

"So while gravity is nearly strong enough to cause some things to fall that far, through air, in the observed interval, and while gravity is probably not strong enough to have so thoroughly disintegrated the towers under their own weight, gravity is certainly not strong enough to have done both at once."

Thanks for posting article.

(I should have also said that the pulverized material was beating the collapse in falling - and off the sides of the towers - how could it possibly have caused the floors below to collapse.)

[DoYouEverWonder]

3. It wasn't just the concrete that was pulverized

Most of the contents of the buildings were too. The desks, the file cabinets, the water coolers, the computers, even the people, everything was pulverized. An enormous amount of energy is required to pulverize a 105 story building and everything inside and something had to generate that energy and it wasn't the crash and it wasn't the fire. There are only a few things in the world that can turn a building into a volcano and last time I checked there weren't any volcanoes under Manhattan Island.

[tenseconds]

6. obvious

Its just so plainly obvious. I think the illustations show how absurd the whole OCT argument is.

[Carefulplease]

18. Why is that obvious?

Why is that obvious that a tower weighing hundreds of thousands of tons and falling from an average height of 680 feet wouldn't deliver enough energy to crush and flatten most of its content? Is it obvious that it would crush some smaller fraction of the material? What fraction would that be and how do you arrive at a reasonable estimate without calculating anything?

[leftofthedial]

21. it might very well crush and flatten everything

but it's not possible for it to do that in the same time it would take for it to fall the same distance through empty space, which is what the OCT says it did.

[Carefulplease]

28. And so "OCTers" are wrong to say that the towers fell at g.

Indeed many "OCTers" and "Truth Seekers" alike agree on good grounds that the WTC Towers didn't fall that fast.

Edited to add: see message #15

[leftofthedial]

30. I think the truth is closer to the official time

than the time quoted below

it's still WAY too fast to have fallen if the OCT is true.

[tenseconds]

35. obfuscation

You're obfuscating the intention of the post. Please address the issue at hand...resistance.Arguing over the collapse times within a 5 second variance is not really what were discussing here.

[Nozebro]

37. True, but it does serve their purpose - which, among other things, IS

to obfuscate. Another example (# 1 million 55) of why 9/11 Truth Seekers should stop wasting time on physical evidence that the Gov't can provide an endless array of experts to give their "opinion" about, namely, that it confirms the Official 9/11 Fairy Tale. Better to AVOID confronting the Truth Suppression Army if your mission is to get the truth out.

[Carefulplease]

40. It is a bit disheartening...

It is a bit disheartening that when some posters actually provide references and arguments in support of their claims, they are accused of being obfuscators.

The discussion of a 5 second variance in a collapse time that is variously estimated to have lasted 9 to 16 seconds certainly is an issue -- unless, that is, we are to stick to naive intuitions and dismiss any quantitative arguments grounded on actual measurements and the laws of physics. Much smaller variances in one tower's rate of fall could be accounted for by a variations of more than an order of magnitude in the resistive force. See Frank P. Greening's paper that I've referenced earlier.

The duration of the collapse isn't the sole issue, of course. I've addressed it in message #15 and I've also addressed the issue of dust expulsion in message #29 and the issue of mechanical resistance from the structure below in message #25.

[Carefulplease]

51. Here is the reference again...

http://www.911myths.com/WTCREPORT.pdf

[Klimmer]

72. Here is your answer . . .

Momentum Transfer Analysis of the Collapse of the Upper Storeys of WTC1
Gordon Ross:

http://worldtradecentertruth.com/Journal_5_PTransferRoss.pdf
http://www.journalof911studies.com/

[Carefulplease]

128. There are quite a few problems with Ross's analysis...

http://worldtradecentertruth.com/Journal_5_PTransferRoss.pdf

I have commented already briefly on this paper. You can search the archive. Here are some further comments.

In this analysis of the energy conditions for the sustainability of the collapse of WTC1 Ross grants that one floor failed and that the upper block of the tower (16 storeys) fell freely 3.7m and impacted the lower section of the tower. He then calculated an energy balance of the process that occur until .02sec after the impact and he concludes that the energy available is fully spent and the collapse can not proceed. His analysis is flawed in several respects.

(1) The very model he uses for his whole analysis is flawed. He assumes that after the upper block has fallen from the height of one storey and has impacted the lower section of the tower there still exists a perfect mechanical coupling between the upper and lower segments of corresponding columns. But these columns -- in a realistic scenario that grants the conditions of collapse initiation -- have already buckled or failed at the splice. It is mostly the upper floor of the lower section that will resist the fall of the upper block. This does not provide the coupling Ross needs to sink the kinetic energy of the block above in the strain reserve capacity of the columns below and above. Ross would rather require, it seems, that 287 column buts below fuse impeccably with 287 column buts above so that the columns load bearing fuctions and strain absorbing capacity be fully restored.

(2) Ross also assumes that after the collision the momentum distribution in the storeys below ranges linearly over a distance of 24 floors below the impact level. Conservation of momentum then dictates that the velocity of the upper block is reduced from 8.5m/s to 4.8m/s and the 25 storeys below acquire velocities that range linearly from (23/24)*4.8m/s to zero m/s. This assumption begs many questions as it builds into the model the assumption that the tower is a giant spring that can absorb the shock of the falling upper block without damage. But the assumption is physically unrealistic. For one thing, it ignores the inertia of the floors and the relative weakness of the floor connections to the columns. This process is supposed to last 0.02sec. This implies that several floors just below and above the impact undergo accelerations or decelerations close to (4.8m/s)/0.02s = 240m/s^2 or 24 times the acceleration of gravity. The only way that I can see to make the model more realistic is to vastly reduce the number of floors involved in the energy absorption during the collision process and this changes the energy balance in a way that is fatal to Ross's argument.

(3) Another major blunder is to count the kinetic energy removed from the upper block after the impact as net energy expenditure in the energy balance. Some fraction of this energy translates into kinetic energy of lower storeys. The rest is "lost" to the extent that the collision is partially inelastic. However the former still is available to produce damage down the road and the latter already *has* been expended doing such damage. In short Ross counts the amount of money spent as a further expenditure and thus he counts it twice!

I have other minor quibbles but each on of these flaws seem sufficient individually to compromise Ross's conclusion that the collapse ought to be arrested.

As an adendum, if you want to read the paper carefully take notice that many occurances of a mysterious factor 10 appear to be typos when some factor 1000 (or .001) is required instead. I am also unsure avout the last "/2" in the calculation of the "Compression of impacted section = 24MJ". There also seems to be some confusion at time about wether 16 or 24 storeys below the impact point are being considered. There are further minor issues.

[Carefulplease]

168. Some more problems with Ross's analysis...

I've found this interesting discussion of Ross's paper on another forum. The poster points out some more flaws in Ross's model and calculations.

http://forums.randi.org/showthread.php?postid=1822297#post1822297

[salvorhardin]

4. I'm a little confused

(I should have also said that the pulverized material was beating the collapse in falling - and off the sides of the towers - how could it possibly have caused the floors below to collapse.)

Why should whether the material is pulverized or intact affect its' mass or affect the degree to which it is susceptible to gravitational attraction? A ton of sand will fall at the same rate as a ton of bricks.
http://www.neuralgourmet.com/2006/08/01/the_falcons_feather_and_the_hammer

[tenseconds]

7. omissions

You're omitting the resistance of the lower section which in case of the South Tower was at least 5 times the weight of the moving mass. And you're also omitting the amount of energy required to pulverize all the materials into find dust which would have dissipated the gravitational energy profoudly.

[salvorhardin]

9. No, I was misunderstanding the poster

I thought she was implying that once the material was pulverized it should somehow have weighed less.

I see now that what she's saying is that because some material was ejected into the debris cloud surrounding the tower that there should have been less mass bearing on the floors below. At least I think that's what she's trying to say.

[quickesst]

31. Yes....

they will fall at the same rate. IF the sand is in the form of solid blocks, you know, like bricks. Drop a ton of loose sand from a hundred feet, then drop a ton of bricks from the same height. The lame analogies the OTC keep coming up with might as well be an open statement that says, "HEY, WE'RE DESPERATE!! In fact, comparing sand, which is much heavier than the dust everyone witnessed, is deceitful at the least. You guys need to get together and come up with some groundrules on what is lame, and what might get by as a credible analogy. Work on it, then get back to us. Thanks.
quickesst

on edit: Let me say that I am dumbfounded and amazed that the "pancake theory" is still being discussed in a serious manner. Is this forum on a loop? Same old discredited shit keeps coming around time after time after time. What a merry-go-round we have.

[Carefulplease]

41. Bad analogy...

If you drop a ton a loose sand in air from a hundred feet, the sand will disperse and traverse a volume of air that is possibly heavier than one ton (Air weigh about 1gh/m^3).

When the towers collapse, the only air resisting is the air within them. This is roughly 1,600,000kg of air. This only represents 0.5% of the mass of the towers (around 300,000 tons each). The resistance this would provide to the falling tower would be negligible even had they wholly turned to dust in an instant.

[Ferry Fey]

5. Material in clouds of debris was not adding sufficient weight?

(I should have also said that the pulverized material was beating the collapse in falling - and off the sides of the towers - how could it possibly have caused the floors below to collapse.)

Do you have a typo there, Tabatha? Did you mean to write "if the pulverized material was beating the collapse in falling"?

I'm glad to see this question coming up. I posted a similar question in a thread here this summer, but didn't get any reply. I wanted to know if there were any attempts to figure out what proportion of the debris was floating in the air, thinking that if it was in the debris cloud, its weight would not be coming to bear on the lower floors.

[tenseconds]

8. pulverized material

The pulverized material was traveling faster than the collapse because it was propelled by explosives and thus its speed would exceed that of gravity.

[salvorhardin]

10. That makes no sense n/t

[AZCat]

13. Gravity isn't a speed.

It's a rate of acceleration - perhaps that's what you meant?

[tenseconds]

14. falling objects

Objects falling have a rate of acceleration

[AZCat]

24. No shit.

So why did you use the term "speed" if you meant "acceleration"?

[tenseconds]

34. listen up dude

I didn't say "gravity is a rate of speed".

[AZCat]

52. Actually, you did.

In post #8 of this thread you stated:

...thus its speed would exceed that of gravity.

Since you are comparing the two you imply that they are of equivalent units. This is equivalent to saying that gravity is a rate of speed.

[whistle]

108. Actually Einstein suggested that gravity was something else...

definition for gravity
(physics) The force of attraction between all masses in the universe; especially the attraction of the earth's mass for bodies near its surface; "the more remote the body the less the gravity"; "the gravitation between two bodies is proportional to the product of their masses and inversely proportional to the square of the distance between them"; "gravitation cannot be held responsible for people falling in love"--Albert Einstein

[greyl]

115. Not really. Force of attraction can be expressed by rate of acceleration.

In relative terms.

[tabatha]

11. yes and no

If it was. Certainly a valid observation.

But it did seem as though most of the material was being pulverized and ejected from the building.

Also, when I wrote that, I had in mind a comment made by one of the OCTers that the building could not have been in free fall - because the pulverized material was falling faster than the building was collapsing - i.e. the material was in free fall down the sides of the tower, and the tower collapse was slower, and thus not in free fall. By extension of that argument, if the material was falling faster, down the sides of the building where it could be observed, than the building - then the material was not exerting the necessary pressure (un-pulverized) on the floors below to cause collapse.

Even if some material was not pulverized, the smaller amount of material falling on floors below should have resulted in a slower collapse (not accelerated as happened).

[Carefulplease]

29. "It did seem as though most of the material..."

But it did seem as though most of the material was being pulverized and ejected from the building.

How would you know that? Do you know what a dust cloud comprising 200,000 tons of pulverized material looks like? How different is that from one comprising *only* 20,000 tons of material?

Analysis of dust samples around Ground Zero revealed that this dust contained as much gypsum as it did concrete. Let us consider just the concrete that made up the floors of the WTC Towers. This was 4 inches thick (lightweight concrete) in the tenant spaces and 5 inches thick (regular weight) in the core. Just assuming an uniform thickness of 4 inches for simplicity, let us suppose that just 10% of the concrete (and nothing else) was reduced to dust and ejected during the collapse. The footprint of one tower is about 1 acre. So 10% of the concrete reduced to dust would account for an average thickness of dust of one inch deposited on a net area of 88 acres (~66 football fields) of lower Manhattan. (That is 2towers*110floors*4inches*10%). I also assume the the dust is packed dense enough that its density is the same as the density of the slab it came from.

What would such an amount of dust look like if it were expelled from the falling towers? Are you quite sure that it really looked like more than 10 times this amount of dust has been expelled? How would you know?

[DoYouEverWonder]

12. Did anyone see an American Vesuvius?

They ran it on the History Channel last night. The program looks at the destruction of the Roman cities of Pompeii and Herculaneum by the eruption of Mount Vesuvius and then compares that event to the destruction of the twin towers on September 11, 2001 using forensic research techniques.

The fellow talked a lot about the shock wave that went out in front of the plumes and how the plumes flowed around things like rushing water would. Pretty interesting analysis. The big different between the two events being that the volcanic dust and air was extremely hot, while the dust clouds in the WTC collapse were cool.

What on earth could cause this type of reaction?

[Carefulplease]

16. The energy released by the detonation of 150 tons of TNT...

The energy released by the detonation of 150 tons of TNT would reduce to dust a fair amount of concrete, gypsum wallboard, ceiling tiles, blaze-shield fireproofing material, etc. This energy would have to be efficiently applied to the material. The collapse of a 300,000 ton, 110 storey high WTC Tower would release roughly that amount of gravitational potential energy in the most efficient possible manner while loosing a minimal amount to heat.

[tenseconds]

20. what are you talking about?

The building as a whole didn't collapse. The lower section was much heavier than the top section and would have given it resistance. It didn't. CD.

[Carefulplease]

27. The towers sure as Hell did collapse...

And they collapses fully but for a few bits of standing perimeter walls and core columns. The issue is the availability of the energy to produce the dust and crush office materials. The gravitational potential energy stored in the towers was plenty. Or do you claim that much more than the energy released by 150 tons of TNT would have been needed? On what ground would you claim this?

[tenseconds]

33. re:gravitational energy

The gravitational energy from the TOP floors was not sufficient to continually crush everything floor by floor into minute dust particles and also contend with the resistance of the lower section.

[Carefulplease]

42. The top floors didn't have to do this...

The top floors only had to destroy the supporting structure below. Most of the crushing of the different materials would have occurred when the bulk of the mass of the whole towers hit the ground. What we see on videos is consistent with just a small fraction of the mass of the towers being crushed and expelled in the early stages of the collapses. What we see at first must have been mostly smoke and then such light and brittle things as gypsum, ceiling tiles blaze-shield, paper sheets, sooth, and so on.

See also message #29

[DoYouEverWonder]

53. Why did the top of WTC2 tilt

but then seems to have righted itself when the collapse began? This seems to defy the laws of gravity?

[Carefulplease]

56. The upper section of WTC2 tilted because...

The aircraft hit the South Tower on the south side where it punched a hole. One engine and one landing gear exited through the north-east corner. The core columns in the south-east corner were in the trajectory of the aircraft. The fires that were mainly located on the east isde caused truss floors to sag an pull on the east wall. This wall was seen to bow inwards long before the collapse. The upper section tilted progessively towards the east bowing wall and the south damaged wall. Those two walls and the south-east corner obviously failed first. That is why the upper section gained some angular momentum in the way that was observed.

Why some of that momentum was reduced while the upper block fell is anybodies guess. It is certainly no inexplicable. The rotational component of the momentum was obviously much smaller than the downward linear component. Jones's suggestion that gravity can not account for its progressive reduction is a red herring. It is obviously the inhomogeneity of the interactions between the upper and lower sections in the collapse zone that would be responsible -- whether or not explosives had been used -- for the application of some torque on the upper section. The event is just too chaotic for any definitive conclusion to be drawn. My guess is that since the upper block tilted towards the south and east, the south and east walls below offered some resistance to the falling upper block while only the floor connection resisted the other two walls that were also falling within the perimeter of the lower section.

[tenseconds]

58. angular momentum

The top section should have proceeded to fall at about a 20% angle.It didn't.It did not adhere to the physic's Law of Angular Momentum. The lower floors began to disintegrate before there was any gravitational action.

[Carefulplease]

62. I don't see any violation of any law of angular momentum...

The upper section did not fall in a vacuum. Why do you believe the disintegration of the lower floors and columns not to be a consequence the action of the upper block falling on them? If anything, the change in angular momentum is evidence that that such mechanical action produced a torque. This can equally be construed as evidence *against* the theory that the lower structure was removed in advance of the arrival of the collapse front.

[DoYouEverWonder]

59. Here you saying

that the top floors tilted has a block?

If it did how did it overcome the momentum all that weight would have created and not continue to topple in one piece (more or less)?

[Carefulplease]

63. It did not overcome the momentum...

It did not overcome the momentum gravity imparted to it. It clearly fell down on the lower structure. After all the perimeter and core columns had been severed, gravity no longer applied a torque on it. I explained in the message you just replied to how the resistance from the east and south walls might have been responsible for a torque in the other direction. The tilting caused the perimeter walls of the upper block to wedge inside the lower perimeter section. Because of the way the block tilted away from the north and west walls, they would not have provided a compensating action. How is that speculation any worse than some unspecified action from explosives?

[tenseconds]

69. specific action of explosives

There is a specific action of explosives on the lower floors of the top section as evidenced by its much darker coloration than the dust clouds of the floors exploding simultaneously below it. You are right in that the peerimeter and core columns were severed on the floor(s) just below it but by the use of superthermate.

See http://www.checktheevidence.com/911/Thermite2.htm

[Carefulplease]

73. Of course that is the smoke from the fires that is being expelled. n/t

[tenseconds]

100. dark smoke

The dark smoke from the fires never penetrates into the lower section but is expelled above the lower section. That is because the lower part of the top section is being demolished before it begins its gravitational fall.

[DoYouEverWonder]

71. Do I understand you correctly?

Are you saying after the building tilted, the perimeter walls from above, fell inside of the perimeter walls below it?

[Carefulplease]

74. That is correct...

Several videos confirm this. They show huge sections of the perimeter walls from the lower section being peeled off like banana peels and falling outwards while the collapse proceeds and the floors are being removed from impacts coming from above. NIST's observations on the modes of failure of truss seats are consistent with this.

"The damage to truss seats on perimeter panels differed above and below the impact zone. The majority of perimeter panel floor truss connectors (perimeter seats) below the impact floors were either missing or bent downward. Above this level, the failure modes were more randomly distributed. This trend was observed for both towers."

http://wtc.nist.gov/NISTNCSTAR1-3Cchaps.pdf
p. xlvii

[DoYouEverWonder]

78. So the perimeter walls

of the lower section peeled away and the top fell down into the inside of those walls? Sort of like a set of cups, stacked on top of each other?

[Carefulplease]

79. Simple geometry...

Consider that the projection of a square slanted around one diagonal is a diamond that will fit in the original square. So the "footprint" of the slanted top section would wholly fit in the square perimeter of the lower section except possibly for the regions closest to the two corners that approximately define the axis of rotation. This allows the upper section to "wedge" inside the perimeter of the section below. Of course, two walls (east and south of WTC2) of the lower section will be hit by the corresponding walls of the upper section from several floors above -- because of the slanting. This would be the reason for the torque I mentioned as a possible cause for the reduction of the angular momentum.

[DoYouEverWonder]

81. That's a great theory

but that is not what happened to the top of the building.

The top of the building did not maintain its integrety and twist on its own axis.

[Carefulplease]

82. I am unsure what you mean...

I did not say that the top section maintained its integrity. It clearly went crashing down and soon disappeared in the opaque cloud of smoke and dust; it might have disintegrated from the bottom up but it clearly did so at a slower rate than did the bottom section. It alone isn't responsible for crushing all the floors on the way down. The already crushed stack in the middle continues to fall on the floors below.

Also, why do you say that it did not "twist on its own axis"? Already before it fell (before the yield of the south-west corner), it clearly has rotated quite a bit.

[DoYouEverWonder]

83. Have you ever used a zoom lense?

The pic that I posted above is from a high powered zoom lense. Lenses like this tend to flatten images and that cause a certain amount of distortion. You need to look at this event from the other sides of the building too and then compare the images. Then you can see what really happened to the building.

[Carefulplease]

86. How is that particular picture misleading?

In what respect do you suggest this particular picture is misleading? My description of the collapse of WTC2 is based on the pictures and videos I have seen over the last few months. I proposed my interpretation before you posted that particular picture (that happens to be consistent with my description). Have you seen some picture of video of the collapse of WTC2 that shown something that isn't consistent with what I have said?

[DoYouEverWonder]

91. Here's the same event from the SSE

What does it look like now? Keep in mind this picture has a lot less distortion then the one that is from the ENE.

[Carefulplease]

98. What does it look like to you?

I just have no idea what feature of the collapse you want to draw my attention on.

[DoYouEverWonder]

110. I want you to look at the top section of the east wall

Look at the the edge of the south side and across the top. They are still all one piece. The building isn't tilting or twisting. The east wall of the top 20-25 floors separated from the building in one piece and is falling out away from the building not into it.

[Carefulplease]

129. You seem to misunderstand...

The downward continuation of the south-east edge clearly appears to meet the lower section inside the perimeter (several feet west of the east wall). Of course, further above the tower leans outside of the perimeter, this is what I have been saying all along and it is essential to my argument. It *has* to hit the east wall below to produce the torque that I want.

What do you mean when you say that "The building isn't tilting or twisting"? It clearly seems to me to be. Do you mean the lower section? I do not get you point or its relevance.

(Edited to remove claim that goes beyond the evidence presented in the picture)

[tenseconds]

80. molten iron

You can see beads of molten iron from the thermate reaction falling from the collapse point. Notice the slight orange glow in that area.

[vincent_vega_lives]

87. Thermate!

:rofl: gets me every time.

[Nozebro]

154. Your post is based on long-disproved premises.

To understand why, read this article.

http://www.911research.dsl.pipex.com/ggua175/

[Carefulplease]

157. This site is totally irrelevant...

This is written by a no-plane theorist. The no-plane theory has no relevance whatsoever to my response to DoYouEverWonder who asked about the tilting of the upper block of WTC2 and the conservation of angular momentum.

On edit: Actually he asked about "the laws of gravity" but angular momentum was clearly the issue.

[Nozebro]

158. You obviously didn't read it & the author is no more of a "no-plane"

theorist (whatever OCT'ers mean by that) than you are a theorist of "incompetence, coincidence, and intel failures" as a (made-up) fairy tale to try and explain the Official 9/11 fairy tale of how
explosions had nothing to do with the historic, catastropic, unique collapse of three steel-framed buildings into their own footprints...as the result of heat.

[Carefulplease]

160. Have it your way then...

He believes that all the witnesses have been fooled by some airborne holographic illusion, that all the footages are faked and that either no aircraft hit the WTC Towers or something else than Boeing 767-200s hit them. He has pretty much nothing of substance to say about the collapses. You response is totally irrelevant to my discussion of the angular momentum of the upper block. You haven't shown that my post was "based on long-disproved premises".

[whistle]

109. Is this science which your are basing this on? If so, could you

...supply whatever scientific proof you believe supports this arrgument so that the rest of us can follow the logic? Thanks.

[Carefulplease]

131. I can provide references...

But you can also do some research on your own. Here are some useful keyphrases: "blast fragmentation", "fracture energy of concrete", "energy conversion". Some useful data are:

Height of the Twin Towers: 415m.
Various estimates of their mass: 250 to 500Mkg each (I myself used the 300Mkg figure)
Potential energy: mass * g * height

One useful paper: F. R. Greening, Energy Transfer in the WTC Collapse.

As for the ground for my claim that kinetic impact is more efficient than explosive blast to produce mechanical damage, this seems self evident to me. The latter looses a big fraction to directly heating air. (Much of the resulting expansion isn't put to useful mechanical use.) The former is mostly only "lost" to direct mechanical damage and thus not lost at all for our present purpose. A little heat is produced through friction and plastic strain. But the explosive method yields identical indirect losses.

[rman]

54. WTC collapse dust clouds may not have been cool

It is the violent turbulence of the dust cloud that makes it look like pyroclastic flow, such turbulance is typically caused by heat.

This is what the dust cloud did to cars:

[Carefulplease]

60. This was nothing like a pyroclastic flow...

Hundreds, maybe thousands of people got caught in the dust cloud from the collapses of both WTC1 and WTC2. Temperatures in excess of 400°C or even 100°C (let alone Hoffman's fantastic 1000°C) would have been noticed -- to say the least. How did people escape the fate of the vehicles shown on these cherry-picked images? How come so many paper posters, trees and other vehicles (that were found crushed under debris but unburned) close to Ground Zero have been spared?

Flaming debris from the collapsing towers ignited hundreds of small fires all around. Most were left unattended for a long time because so many firemen had either been killed or were focusing on rescue efforts. Some vehicles caught fire and burned out. When their gasoline tanks broke or exploded, the fires were propagated to nearby vehicles. There is no need, to account for, to posit an imaginary pyroclastic gas flow that nobody noticed.

[tenseconds]

101. look at the flow

[Carefulplease]

130. The issue is the temperature of the flow.

A cold pyroclastic flow is an oxymoron. Pyros = fire.

The flow in itself has nothing puzzling. The collapse of each tower displaced 2 million cubic yards of air (some significant fraction of which was quite hot from the fires) over a distance of 1360 feet within 15 seconds. Some lukewarm dusty breeze is to be expected.

[tenseconds]

134. wary

You're not puzzled by the blown out windows of all the cars etc? Just a "lukewarm dusty breeze".You got an answer for everything..that in itself makes me quite wary of you.

[Carefulplease]

139. What makes you think that dust blew the car windows?

Apart from the dust there rained down over a large area several thousands of tons of debris of various sizes. Why wouldn't that, rather than dust, account for some of the damage to some of the cars? Fleeing people that still were close to the towers when they collapsed and who survived the falling of the debris also survived the dust just fine -- apart from some breathing and ocular problems.

I do not have an answer to everything. I have answers some of the issues raised in posts I choose to answer to. When I do not feel knowledgeable I either do some further research or I just read what others have to say.

[DoYouEverWonder]

68. I don't know what blew those cars up

but each one has a source of fuel and something caused that fuel to ignite.

However, the people that were in the cloud and survived did not get burnt. That means the dust cloud was relatively cool. What would cause that?

[tenseconds]

70. how about

The power and expansiveness of the turbulent dust flow coming through the street created enough pressure? I noticed in one of the photos that a car's front hood was blown open.

[Carefulplease]

75. There was a vast area in which debris rained down...

The sizes of those debris ranged from small pebbles to multi-tons pieces of steel. Some of the debris were flaming. They ignited fires in many surrounding buildings. What more do you need?

(Can "debris" be used as a plural in English?)

[DoYouEverWonder]

77. There was no flaming debris falling

The flames got snuffed out very quickly with all the dust and the effects of the collapse.

However, anything that was made of metal that was actually in the fire like steel beams would still be hot and would reignite any flamable debris that feel on top of it.

[vincent_vega_lives]

88. The THERMATE fell on them

:rofl: and went on to core of the earth.

[DoYouEverWonder]

90. Are you implying

that the steel wasn't heated up by the fires?

I said nothing anywhere in this thread about thermite.

I'm so glad you get such a kick out of yourself. Real comedians don't laugh at their own jokes.

[vincent_vega_lives]

97. No

But thermate (as opposed to thermite) is brought up so much lately, once it has been learned as a proper CT buzzword. It was "Shaped charge" and "squib" for a while, but those have apparently fallen out of favor.

I never claimed I was a real comedian.

[tenseconds]

119. thermate

Become familiar with Steven E Jone's research. Do you know the difference between thermite and thermate?

[vincent_vega_lives]

123. Yes I do

And I have looked at his research. The mentioning of thermate (or thermite) still makes me chuckle.

[tenseconds]

92. lots of

Lots of crinkling and disfiguration with autos and particularly the bus. Pressure from the dust furies.

[vincent_vega_lives]

103. dust had nothing to do with it n/t

[greyl]

132. debris - plural

"(Can "debris" be used as a plural in English?)"

Interesting question. Debris can be singular or plural depending on qualifying words. Like junk, heat, music and... math. ;)

With 3 pieces of debris, it would be "3 pieces of debris were", not "was".
With the debris, it would be "the debris was"
With some debris, like in your sentence above, it would also be "some of the debris was".

[Carefulplease]

140. Thanks Greyl. That's quite useful. n/t

[greyl]

142. (hoping you got the maths joke)

[Carefulplease]

150. The maths joke...

Removed (bad joke)

[Carefulplease]

15. It is just plain false that the Twin Towers were essentially free falling

All the direct quantitative estimates of the acceleration of the falling upper blocks of the Twin Towers yield values that are significantly lower than 9.81m/s^2.

First, note that Jim Hoffman estimates from the examination of a video that the duration of the collapse of WTC1 is approximately 15 seconds.

http://911research.wtc7.net/essays/reynolds/
http://911research.wtc7.net/wtc/evidence/videos/ntc_frames.html

One contributor to the PhysOrg forums (Neu Fonze) has measured the positions of the upper blocks of both towers on successive videoframes and he get an acceleration that tends towards a value significantly lower than g.

http://forum.physorg.com/index.php?showtopic=7444&view=findpost&p=106164

This is shown by another contributor to be consistent with both Hoffman's observation and Frank Greening's momentum transfer analysis (and also with Greenings measurements of the rate of descent of the tower upper blocks using a technique similar to Neu-Fonze's.)

http://forum.physorg.com/index.php?showtopic=7444&view=findpost&p=106249
http://www.911myths.com/WTCREPORT.pdf

Finally, Gordon Ross also rely data from video analysis and he produces results that show the antennae and roof line of WTC1 falling no more than 100 feet in the same time a free falling object would have fallen 145 feet. This is also in broad agreement with Greening's, Neu-Fonze's and Hoffman's observations.

http://gordonssite.tripod.com/id2.html
http://forum.physorg.com/index.php?showtopic=7444&view=findpost&p=120958

We thus have broad agreement from critics and supporters alike of the several theories on offer -- who have actually measured and not just guessed -- that the actual collapse of the Twin Towers took place with accelerations significantly lower than the acceleration of gravity (roughly 2/3).

[RedSock]

17. time of collapse

First, note that Jim Hoffman estimates from the examination of a video that the duration of the collapse of WTC1 is approximately 15 seconds.

that means each floor offered an average of less than 1/4 of a second of resistance (80 floors or so below impact zone)

if each floor has resisted for even one-half second, the collapse would have taken 40-45 seconds.


edit: (not meant to endorse any theory ... just sayin')

[Carefulplease]

25. Of course...

If some floor had resisted 1/4 of a second then the mass falling on it would have essentially come to rest. This means that the total kinetic energy of the falling mass would have been absorbed before that floor gave way. Is that a reasonable assumption? It seems merely to posit without argument that an average floor is capable of absorbing the energy of a significant portion of the tower (10 to 25 floors) falling on it from more than 12 feet. This is merely begging the question.

Consider that after collapse has been initiated, all the 287 core and perimeter columns have given way. So, during the fall, when the lowest intact floor of the upper block meets the highest intact floor of the lower section, the corresponding column segments from above and below are no longer supporting each other. The bulk of dynamic load of the upper block gets applied to one single floor below. This floor is attached to the columns of the lower section. The beams and trusses and their connections to the columns are designed to resist not much more than the dynamic load on *one* floor directly above falling on them. But now there are not only 10 office floors falling on them but also ten floors worth of core and perimeter columns plus other heavy structures such as the hat truss and the upper mechanical equipments. The resisting floor can at most remove some fraction F of the kinetic energy mgh = ((1/2)mv^2) of the falling mass (where F < 1). This means that the speed of the falling mass just after that floor gave way isn't smaller than v*sqrt(1-F). So, even if fully 25% of the kinetic energy of the falling upper block was consumed in disconnecting that floor, the speed of the of the upper block would only be reduced by 13.5%. (I am putting aside for the moment the effect of momentum transfer -- the energy needed to accelerate the floor below from rest to the speed of the falling stack)

Even if we disregard that the falling mass gets progressively heavier as the collapse proceeds we can see that when the upper block has fallen through n lower floors, it has gained the total kinetic energy K = n*mgh - n*F*mgh. Assuming constant loss of kinetic energy ((25%)*mgh) at each step, its final speed is thus also reduced by only 13.5%. This means that the effect of the constant resistance is to reduce the effective force of gravity by 13.5%. That is not much of an effect. The effects of momentum transfer are much more significant than this. They are discussed and calculated in a paper by Franck P. Greening referenced in another message of this thread. These effects also include the energy used up in crushing concrete and other stuff during the first stage of the collapse before the falling pile hits the ground.

[tenseconds]

36. pancaker

You're really giving argument to the pancake theory.There's no real answer for the emulsification of material here. Also there would be a constant deterioration of the top section on its way down as it represents a block of floors connected together not one single solid unified mass.

[Carefulplease]

43. There probably has been...

There probably has been such a progressive destruction of the top section. However the rate of destruction of the top section would have been smaller than the rate of destruction of the section below since the middle layer comprising an ever-increasing number of already crushed and compacted floors is accelerating downward. So, the impacts on the floors below would be much more energetic than the impacts on the floors above and would occur at a higher rate.

[tenseconds]

38. miracle

Consider that after collapse has been initiated, all the 287 core and perimeter columns have given way.

That's quite a feat in itself, isn't it. A miracle of heat distributiion.

[Nozebro]

39. 9/11 OCT = "A Course in Miracles" and all are invited to profess their

belief and faith, then line up and sign up to become a member of the "Faith-Based" 9/11 Support Group.

[Carefulplease]

45. Not quite a miracle...

The failure of the columns is progressive but when the overall demand (the total loads) come to exceed the overall capacity of the columns then the failure of the remaining intact columns would occur in very quick sequence. There is no other way for them to occur. The damage from the impacting aircrafts from the ensuing fires account for the conditions that lead to collapse initiation. However, collapse continuation and its rate are the issues being discussed in this thread. You ought to grant the possibility of collapse initiation for the purpose of discussion. Otherwise the whole issues being discussed here would become moot.

[Nozebro]

47. Even Bush has been forced to hint at the truth of CD. The wheels are

beginning to come off. That means OCT'ers here will soon start saying: "yes, BUT. yes, but NO ONE could have predicted Bush would admit that and now that he has...hey LOOK. It's Osama holding up a copy of the purchase order for...for - does that say THERMITE? SEE, we told you all along that Osama was a competent EVIL Doer."

[freedom fighter jh]

102. The columns are the whole issue

What happened to the columns?

The columns were holding up the buildings. Once the columns collapsed, the rest of the buildings had to collapse.

Just what happened to them? Did they simply buckle? If so they would have remained standing, each column in one piece. Did each column break into two pieces, each several hundred feet long? If so, they would have been visible after the collapse. After all, the towers measured only 200 feet on each side, so 94 pieces each 500 feet long would have stuck out from the rubble. Or did they break into much smaller pieces, or perhaps melt? It must have been one of these things, because these are the only possibilities left. The longest pieces of steel beams documented in the NIST report were about 40 feet long. I'm using that as a best guess for the longest pieces that were produced. It has to be a guess because, as you know, most of the steel was not left available for examination.

You are absolutely right to consider energy. What was the source of the energy that broke each of 47 massive steel columns into 30 pieces each? One would need a steel manual as well as specific knowledge about the columns to try to calculate that amount of energy. It would be equal to the force required to make each break in each column (or otherwise cause the column to break into pieces), times the distance through which that force would act, times the number of breaks per column, times 47, the number of columns. Remember that these columns were built strong enough so that together they could hold up a 110-story building, and they did that for a quarter of a century. Intuition tells me that that energy is many times the building's potential energy, the energy that was available in the fall. By my calcs, the buildings lost less than 20% of their potential energy in the fall. That 20% would have had to shatter the columns, pulverize the concrete, and accelerate the air to gusts.

Not plausible. Something that is not in the OCT destroyed the columns.

[whistle]

111. The 47 center support columns were each built strong enough to hold up

...themselves first and then together they could hold up the remainder of each 110-story WTC tower building, plus the static weight of all of the contents, machinery, equipment and people which were elevated above ground level, plus a factor for safety above the expected combined maximum of that total weight. In addition, those support columns had to also withstand all expected natural <i.e. winds, earth shifts, water> and not so natural <i.e. fire, explosions, multiple airplane crashes> external forces. That was the total and complete function of those 47 center support columns, tested and proven to be so up until the 9/11 crashes of only one aircraft into each tower. On that morning supposedly all 94 center support columns failed causing the whole superstructure to come down in an "explosive and cataclysmic" manner, but in a precise way as to cause most <90%+> of the bulk of the debris which had not been converted to 100 micron or smaller particles in each of the WTC tower's own footprints.

Now, there are many people who want to know how and why this could happen to a structure like the WTC which was designed to resist the most likely causes of such an event including large airplanes crashing into multiple floors of the WTC towers. The official explanation <so far only one has been brought forward: that of high impact; fire; excessive heat; and structural failure> does not appear to hold up under close scientific examination or various visual records in the forms of films archives, expert testimony, new evidence or eye witnesses.

Since most of these additional pieces of information were never taken into account under the official investigations and explanation, the American public, the families of the victims, and all of the human beings who were affected by the events of 9/11, have the right to demand and get a new investigation to satisfy all of the questions which the official commission report failed to answer or investigate thoroughly.

That is what is asked for and that is what is deserved. Now, do we get it, and if so by whom and how quickly?

[Carefulplease]

151. Intuition and calculations...

Remember that these columns were built strong enough so that together they could hold up a 110-story building, and they did that for a quarter of a century. Intuition tells me that that energy is many times the building's potential energy, the energy that was available in the fall.

Unless you are an experienced structural engineer you can safely dismiss your intuitions about such things. And if you are an engineer then you ought to be able to provide arguments to ground such intuitions.

By my calcs, the buildings lost less than 20% of their potential energy in the fall. That 20% would have had to shatter the columns, pulverize the concrete, and accelerate the air to gusts.

How do you get to this 20% figure? How did you calculate that? Whatever happened to the other 80%?

[freedom fighter jh]

159. More on the columns

I am a civil engineer by training but not experience. (I am licensed.) As I said in my original post, I lack (as most of us do) specific information about the kinds of beams used in the columns. I also lack a steel reference manual, which, if I knew the kinds of beams used, would tell me the force needed to cause the beams to fail. It would also tell me the beams' dimensions, which would tell me the distance through which that force would act. That would be the energy to cause one beam to fail in one place. (But one would have to check all possible modes of failure and find the one that used the least energy). I hope that answers your question. If you have a clue to this information, I'd like to hear it.

If each column failed in more than one place then you would have to figure in multiple failures for each. Each column *must* have failed in more than one place, since there were no pieces of columns remaining that were several hundred feet long.

Here's how I got 20%: I calculated how long it would take the buildings to collapse in near free fall. By "near free fall," I mean the scenario that seems to me most consistent with the pancake theory: everything above the point of impact falls to the next floor, which is sitting unsupported but unmoving, waiting to be hit. Then gravity plus the momentum of the moving mass cause that floor to slam into the next one, etc, all the way down. I assumed all the energy of motion went into accelerating the next floor down. Realistically, of course, you would not expect a perfectly elastic collision, but I figured this was a good baseline assumption for later comparison. It came out to 9.2 seconds for the tower that was hit on the 85th floor. If the actual time of collapse was 10 seconds, that means the tower's average speed of collapse was (rounding off) 9/10 of what it would have been unimpeded. So (squaring and rounding off) its kinetic energy was 8/10 of what it would have been in freefall.

That 80% became kinetic energy and brought the towers to the ground. What happened to it after that I don't know.

I'm new to DU, as you can see, so I don't know how to post a spreadsheet, if such a thing is possible. But I'm sure you can replicate my calculations, and anyway my 20% is not far from the 25% you assumed in one of your posts.

Those columns had to be strong enough to slow the collapse by more than a hiccup. But to me the more important question is what happened to the columns. Only small pieces were left. How did they get destroyed? What could account for the force needed to make that happen?

[AZCat]

161. Welcome to DU!

Unfortunately DU doesn't have a way to post spreadsheets or tables - we have to do it the "old school" way (just typing it out).

[freedom fighter jh]

162. Thanks!

Thank you, AZCat.

[Carefulplease]

163. Wellcome to DU.

(Edited for typos)

I didn't realize you were new to DU. Wellcome to the discussion.

I am a civil engineer by training but not experience. (I am licensed.)

There are few people with relevant qualifications for the discussion of such issues here. I have no such qualifications myself except for some undergraduate training in mathematics and physics. Your expertise will be appreciated.

As I said in my original post, I lack (as most of us do) specific information about the kinds of beams used in the columns. I also lack a steel reference manual, which, if I knew the kinds of beams used, would tell me the force needed to cause the beams to fail.

Short of a steel reference manual there are heaps of information in the relevant sub-reports of the NIST investigation.

Some information on the column cross sections and the core column schedule close to the impact and fire areas:

http://wtc.nist.gov/NISTNCSTAR1-1.pdf
pp. 23-27

In this sub-report you will find lots information on the steel specifications, mechanical properties and the failure modes of the components:

http://wtc.nist.gov/oct05NCSTAR1-3index.htm

More on the mechanical properties and failure criteria of the steel:

http://wtc.nist.gov/NISTNCSTAR1-6.pdf

Same for other subsystems (perimeter columns and floor truss assemblies:

http://wtc.nist.gov/NISTNCSTAR1-6C.pdf

Some other sub-reports also have much relevant information. You have to dig.

It would also tell me the beams' dimensions, which would tell me the distance through which that force would act. That would be the energy to cause one beam to fail in one place. (But one would have to check all possible modes of failure and find the one that used the least energy). I hope that answers your question. If you have a clue to this information, I'd like to hear it.

You can work with upper bounds. It is not necessary to find the precise failure mode that consumes the least energy. F. R. Greening and Bazant and Zhou have produced idealized models that probably assumed much more energy consumption than is realistic. They had all of those columns buckling at every floor. Still, global collapse proceeded with little impediment. Gordon Ross is the only one that I know who produced a model that predicts collapse arrest some short time after initiation through the failure of one floor. But his model is quite flawed as I have indicated elsewhere in this thread.

If each column failed in more than one place then you would have to figure in multiple failures for each. Each column *must* have failed in more than one place, since there were no pieces of columns remaining that were several hundred feet long.

It would seem that the columns failed at most every splice connection. There was one such on every three floors (or 36 feet). They weren't designed to hold much lateral loads. The perimeter columns and spandrels, and the hat truss, were responsible for the rigidity of the structure and its resistance to wind loads.

Here's how I got 20%: I calculated how long it would take the buildings to collapse in near free fall. By "near free fall," I mean the scenario that seems to me most consistent with the pancake theory: everything above the point of impact falls to the next floor, which is sitting unsupported but unmoving, waiting to be hit. Then gravity plus the momentum of the moving mass cause that floor to slam into the next one, etc, all the way down. I assumed all the energy of motion went into accelerating the next floor down. Realistically, of course, you would not expect a perfectly elastic collision, but I figured this was a good baseline assumption for later comparison.

It seems to me that a good baseline is produced through assuming perfectly inelastic collisions. This must be what you meant to say. Assuming perfectly elastic collisions you would have the upper block, say 16 storeys, transmitting its full momentum to the floor below and the collapse wave would thereafter travel down at free falls speed (each lower floor transmitting its full momentum to the next one at each impact.)

It came out to 9.2 seconds for the tower that was hit on the 85th floor. If the actual time of collapse was 10 seconds, that means the tower's average speed of collapse was (rounding off) 9/10 of what it would have been unimpeded. So (squaring and rounding off) its kinetic energy was 8/10 of what it would have been in freefall.

That 80% became kinetic energy and brought the towers to the ground. What happened to it after that I don't know.

I'm new to DU, as you can see, so I don't know how to post a spreadsheet, if such a thing is possible. But I'm sure you can replicate my calculations, and anyway my 20% is not far from the 25% you assumed in one of your posts.

I misunderstood your claim. I thought you proposed that 80% of the potential energy wasn't converted to anything else. It makes sense that 20% of it produces mechanical damage in inelastic collisions and the rest is converted to kinetic energy of the falling mass. (This would produce more crushing of the content of the heap as it hits the ground plus some heat and seismic waves.) Your spreadsheet calculation is probably correct.

[freedom fighter jh]

171. Do you have a reference for Greening, Bazant, and Zhou?

Thanks for the welcome, Carefulplease.

Wow, you've given me a lot to chew on.

I will check the references you post, but what with other responsibilities in my life I don't know when I can reply.

But I would love to see something that shows there was enough gravitational energy to cause the collapse. Can you tell me how to find the work of Greening, Bazant, and Zhou?

About the spreadsheet: Actually, I meant *elastic* collisions -- collisions in which no energy is lost. I also assumed, and should have said this, that the energy in the downward velocity of the moving piece keeps going in the downward direction. That is an approximation. Realistically, *momentum*, which I did not consider, will be preserved exactly between the two bodies. But when you try to figure that in, it gets more complicated than anything I was ready to deal with (because the top piece might bounce). So I figured conservation of energy would yield a conservative result.

[Carefulplease]

173. References...

Here are the references. I'll comment on your other points in a separate message.

http://www.911myths.com/WTCREPORT.pdf
http://www-math.mit.edu/~bazant/WTC/WTC-asce.pdf

Also of interest:

http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/ProgressiveCollapseWTC-6-23-2006.pdf

And finally the Ross/Greening exchange:

http://worldtradecentertruth.com/Journal_5_PTransferRoss.pdf
http://worldtradecentertruth.com/Article_2_Greening.pdf
http://worldtradecentertruth.com/Article_3_RossReply.pdf

Those last three are from: http://www.journalof911studies.com

[freedom fighter jh]

176. Thanks, Carefulplease

I'll check these out.

[DoYouEverWonder]

164. Good questions

What could account for the force needed to make this happen? There are only a couple of things in the world that I can come up with that could cause the building to disintegrate right before our very eyes. Most of the building appears to pulverize itself spontaneously. Even the NIST folks now admit the building didn't pancake.

Couple of oddities to consider. In WTC 1, the building failed at the 92nd floor which was below the impact zone. Since the floor was not impacted by the plane and fire usually goes up not down, why did this floor fail?

In WTC 2, the building failed at the 81st floor. The 81st floor had some major differences when compared to other floors. The 81st floor housed the dozen 24-ton elevator hoists. Other then that there wasn't much else on that floor so what was there to sustain the fire on this floor? Also, because these hoists were so heavy, the support beams on 81 were twice as big and four times as heavy as the beams on the 79th floor. Amazing that the hijackers were able to hit the building in just the right spot to cause total failure. Someone had to have inside info in order to know how these buildings were designed. A lot of the information available to us now, was not in the public domain prior to 9-11.

Of course, NIST and FEMA preferred to model the event rather then try to recover real evidence such has the columns and beams from the floors that failed. Why not? Every column and beam was marked with a ID number and even every weld was signed by the welder. It would not have been hard to recover the steel from the impact floors to find out what happened to the building but now it's too late.

[Carefulplease]

178. Loss in potential energy...

I seem to have misread this the first time.

Here's how I got 20%: I calculated how long it would take the buildings to collapse in near free fall. By "near free fall," I mean the scenario that seems to me most consistent with the pancake theory: everything above the point of impact falls to the next floor, which is sitting unsupported but unmoving, waiting to be hit. Then gravity plus the momentum of the moving mass cause that floor to slam into the next one, etc, all the way down. I assumed all the energy of motion went into accelerating the next floor down. Realistically, of course, you would not expect a perfectly elastic collision, but I figured this was a good baseline assumption for later comparison. It came out to 9.2 seconds for the tower that was hit on the 85th floor. If the actual time of collapse was 10 seconds, that means the tower's average speed of collapse was (rounding off) 9/10 of what it would have been unimpeded. So (squaring and rounding off) its kinetic energy was 8/10 of what it would have been in freefall.

That 80% became kinetic energy and brought the towers to the ground. What happened to it after that I don't know.

If you assume perfectly elastic collisions then it also gets rather complicated and unrealistic. The top section comprising 15 stroreys (F85-F110) falls as a block until it hits the next floor below (F84) with speed v1. After this first elastic collision this floor moves with an initial velocity that is close to 2*v1 while the velocity of the upper block is reduced slightly. This first impacted floor then accelerates further under the action of gravity until it hits the next floor (F83) with some speed v2 > v1. After the second elastic collision, the velocity of floor F84 is reduced to zero and the velocity of floor F83 becomes 2*v2. The upper block is thus allowed to keep up with F85 and hit it one second time. Thereafter the sequence of collisions become very complicated and chaotic.

The assumption that collisions are elastic amounts to the presupposition that all the energy from the impact is converted into elastic strain energy and fully restored such that the relative velocities of the two impacting masses are reversed. It seems to me to be more realistic to assume that the energy is mostly absorbed in the reduction of the relative velocities through expelling air and producing plastic strain and fractures in the floor trusses, concrete and live load materials. Only some fragments will rebound, not the whole floors.

I would also question your assumption that the collapse duration is 10 seconds. Refer to Greening's paper for more reasonable assumptions and measurements based on video evidence.

On edit: have a look at message #15 in this thread for more references on the collapse times.

[John Q. Citizen]

19. You now trust the conspiracy theorists over NIST? Make up your mind

fer crying out loud.

So you agree that NIST is just guessing?

Even if the figure 2/3 of the free fall time is correct, it still doesn't add up to the NIST hypothysis of how the towers fell.

Time for a real investigation, and this time let's make sure we get it right.

No more of the perpetrators choosing who sits on and runs the investigative body.

There are just too many holes in the official story to believe.

[leftofthedial]

22. "too many holes"

THAT's the problem. We keep getting tangled up in missiles and remote-control planes and holograms and concrete cores, etc.

Bottom line is the OCT is absurd on its face and full of impossibilities, contradictions, implausibilities, known lies, politically convenient nonsense and just enough truthiness to enable the cabal's strategy of obfuscation.

[tenseconds]

23. nastyNIST

Just heard an interview with Kevin Ryan on Guns and Butter http://kpfa.org/archives/index.php?arch=16124

Good info on that nasty NIST crew.

[Carefulplease]

26. Of course NIST is gessing...

Or rather, they are not even trying to guess what the total time of the collapse is. What they say is this:

NIST estimated the elapsed times for the first exterior panels to strike the ground after the collapse initiated in each of the towers to be approximately 11 seconds for WTC 1 and approximately 9 seconds for WTC 2. These elapsed times were based on: (1) precise timing of the initiation of collapse from video evidence, and (2) ground motion (seismic) signals recorded at Palisades, N.Y., that also were precisely time-calibrated for wave transmission times from lower Manhattan (see NCSTAR 1-5A).

http://wtc.nist.gov/pubs/factsheets/faqs_8_2006.htm

The collapse isn't finished when those panels hit the ground. Also, both their data on the start (from videos) and the end times (from seismic data) have a 1 second uncertainty.

They also say:

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.

So, it's anybodies guess what the total time of the collapse was. Those who attempt to guess it from the analysis of video data (such as Hoffman) get something around 15 seconds. This is consistent with the acceleration that others have measured in the first few seconds of the videos when specific features of the towers can be tracked before dust obscures the view.

NIST also say:

Since the stories below the level of collapse initiation provided little resistance to the tremendous energy released by the falling building mass, the building section above came down essentially in free fall, as seen in videos. As the stories below sequentially failed, the falling mass increased, further increasing the demand on the floors below, which were unable to arrest the moving mass.”

This is rather lousy. The structural resistance was indeed little. However the claim does not take into account the more significant effect of momentum transfer from the falling mass to the floors below.

[DoYouEverWonder]

32. The you need to notify the folks at NIST

because according to there latest Q&A memo, they state very clearly that the towers essentially fell in free fall.

[Carefulplease]

46. Please, do not swallow everything NIST claims uncritically...

And read message #26.

(Edited to correct message number)

[DoYouEverWonder]

49. LOL

Now that even the NIST disagrees with you they are no longer credible. ROFLMAO.

The problem with NIST and FEMA is not the people who do the actual work and research. Most of them are ethical and well trained scientists. I am sure given what they've had to work with, they've done their best. The problem is the gatekeepers at these agencies and the information that the gatekeepers choose to present and what they choose to ignore. They know most people will never actually read these reports, because if they did they would see that a lot of what they are finding agrees with what the CTers have been trying to prove for the last 5 years.

[Carefulplease]

50. NIST certainly is credible...

Now that even the NIST disagrees with you they are no longer credible. ROFLMAO.

And whenever they agree with you on some statement they are suddenly authoritative? NIST certainly is credible. The agency employs thousands of career scientists, engineers and technicians, including a few Nobel laureates. This does not mean that every statement from any publication they produce can be isolated from context, given a literal interpretation and accepted uncritically. Any person or organization, however much credibility it has, will also produce inaccurate or misleading statements once in a while. If NIST's claim that the towers fully collapsed essentially free fall meant that this occured within roughly 9.2 seconds then that would contradict the numerical data they provide in the very same document.

The problem with NIST and FEMA is not the people who do the actual work and research. Most of them are ethical and well trained scientists. I am sure given what they've had to work with, they've done their best. The problem is the gatekeepers at these agencies and the information that the gatekeepers choose to present and what they choose to ignore.

No. The present problem is rather your inability to stay on topic or to produce arguments. You didn't address any of the arguments I produced. Do you really believe that the towers fully collapsed within roughly 9.2 seconds or not?

Edited to fix typos.

[Grateful for Hope]

169. Just an observation

I have noted that you have consistently directed CT'er's to the NIST report. It is interesting to me that, when the NIST report does not back your own theories 100%, then it is suddenly not ok to trust that report unquestioningly.

You can't have it both ways, IMHO.

[Carefulplease]

170. Of course I can have it both ways...

NIST is an authoritative source and they have performed the most thorough investigation of the behaviour of the WTC Towers from the time of impact until the time of collapse initiation. I direct towards the report people who would benefit from the information contained therein. This in no way implies that I hold all and every statement that some NIST representative(s) make(s) to be true or that the report and investigation are flawless. People here are just fond of criticizing the NIST investigation while they haven't the slightest clue what its methods, premises or conclusions are.

I've also "consistently", as you say, directed people to research effected by other individuals and organizations -- including individuals who are highly critical of some aspects of the NIST investigation or even defenders of some conspiracy theory or other -- whenever it seems more relevant to me. One can not dismiss issues of authoritativeness of one's source, however my focus always has been on the legitimacy of the data and the soundness of the arguments.

Notice also that the comment in my previous message was sarcastic. It is directed to somebody who clearly wants to have it both ways -- holding one single isolated statement by NIST to be unquestionable and unambiguous regardless of arguments that favour a more reasonable interpretation of the fuzzy and contextual predicate "essentially".

[Brainster]

44. Everybody Focuses on How Fast the Towers Fell

Nobody seems to examine the other side--how fast do controlled demolitions fall? There's an unspoken assumption that they fall as fast as free fall. But looking at the Southwark Towers, for example, they fell in about 7.5 seconds, despite the fact that they "should" have fallen in about 4.5 seconds if they fell in free-fall.

[Name removed]

48. Deleted message

Message removed by moderator. Click here to review the message board rules.

[rman]

55. The point is natural pancaking would not happen at near free fall speed

Because the mechanical resistance of the floors would slow down the falling debris.

[Carefulplease]

57. What does "near free fall" means?

Does that mean that the acceleration is greater than 9m/s? Or greater than 6m/s? What counts as a significant mechanical resistance?

See message #25

[FoxOnTheRun]

61. It shouldn't collapse completly

[Carefulplease]

64. Why not? n/t

[FoxOnTheRun]

65. Isn't there something like the law of the least resistance?

Why should the top-part of the building destroy the whole intact structure underneath?

[Carefulplease]

66. There are two good reasons for that...

The first reason is this. While the columns got progressively stronger on the way down, the floors didn't. Columns had to hold the whole weight of the section of the building above them while floors only had to hold themselves up. When the upper sections fell on the lower sections, all the columns were disconnected so they did not resist the fall much. It is rather the floors that resisted and this resistance did not increase on the way down. However the falling mass did increase. The columns yielded mostly after the floors gave way thus removing their lateral support and allowing them to fail at the splices.

The second reason is that the crushed middle section acted as a buffer between the two other sections. This middle section became progressively heavier while it accreted materials from below (and to a lesser extent from above) and its acceleration approached that of gravity. Hence, the effective weight (and relative speed) of the upper section on the middle section was much reduced.

[FoxOnTheRun]

67. the second reason with the crushed core columns

is the problem, I would really love to see what happens when they are not blown up.

This was not a Jenga tower

[MervinFerd]

85. More like a Jenga tower than an OAK TREE.

A skyscraper is constructed of individual elements connected together. It is much stronger in some directions than others and removing some elements puts stresses on other elements and joints that they were not designed to handle.

Hence, it collapses into a heap; it does not topple over.

And, I'd bet a Jenga tower falls at approximately 'free fall' velocity. Once it starts to come down, the whole thing just falls apart.

[tenseconds]

93. prior

Prior to 9-11,tell me one skyscraper that fell into a heap from gravitational collapse.

[vincent_vega_lives]

106. prior

to 9-11 tell me one skycsraper that fell into a heap from being hit from a airliner moving at near top speed igniting a major fire?

[freedom fighter jh]

138. Columns

What's your basis for saying the columns were disconnected?

If the idea is that the falling floors sheared away the connections, that is a process that would require energy -- and thus would slow the fall.

Are you saying the columns were disconnected because that seems like the only possibility? But is it really a possibility? You say the columns "yielded" once the falling of the floors had removed their lateral support. That's a lot of assuming. As can be seen from construction photos, the columns were braced against one another. They did not depend on the floors for lateral support. And how did they yield? You say they "fail at the splices." Wherever they failed, they would need a mechanism and a cause. Was it in buckling that they failed at the splices, for lack of lateral support? Remember that these are columns that were designed to support lots of floors. Now that the floors are gone along with, you say, their lateral support, their load is lightened vastly -- they have only themselves to support. So what would cause them to buckle? Further, if they did simply buckle, long pieces of them would remain visible in videos of the collapses. None did.

It looks like the only possibility left is that the columns failed first and it was the columns' failure that brought the buildings down. After all, it was the columns that had been holding the buildings up.

The big question remaining is what caused the columns to fail. I have not heard anyone propose a plausible mechanism for how airplane crashes high up in the buildings could do that.

[Carefulplease]

152. Energy and column buckling...

What's your basis for saying the columns were disconnected?

If the idea is that the falling floors sheared away the connections, that is a process that would require energy -- and thus would slow the fall.

That the columns mostly failed at the splices in an observation that NIST makes. You can find this in this report:

http://wtc.nist.gov/NISTNCSTAR1-3.pdf

As for the energy required there seems to have been plenty. Bazant and Zhou, and also F. R. Greening have provided anayses that confirm this. The energy spend in destroying the structure below has an effect on the timing of the collapse that is much less significant than momentum transfer (the effects of the mere inertia of the floors below). These authors even assume that the energy goes into buckling intact and fully braced columns. If you want to question this you have to come up with some specific argument and calculation like Gordon Ross attempted to do.

Are you saying the columns were disconnected because that seems like the only possibility? But is it really a possibility? You say the columns "yielded" once the falling of the floors had removed their lateral support. That's a lot of assuming. As can be seen from construction photos, the columns were braced against one another. They did not depend on the floors for lateral support.

The only braces that there are are floor truss assemblies in (most of) the tenant areas, and beam frames in the core. All of these are parts of the floors. When the floors from the upper block hit and remove the floors from the lower section there are no bracing beams that can remain.

And how did they yield? You say they "fail at the splices." Wherever they failed, they would need a mechanism and a cause. Was it in buckling that they failed at the splices, for lack of lateral support? Remember that these are columns that were designed to support lots of floors. Now that the floors are gone along with, you say, their lateral support, their load is lightened vastly -- they have only themselves to support. So what would cause them to buckle? Further, if they did simply buckle, long pieces of them would remain visible in videos of the collapses. None did.

What causes them to buckle is the combination of both loss of lateral support and the top section (containing such things as 50 heavy elevator motors and the massive hat truss) coming down crashing on them. The top sections of WTC1 and WTC2 got progressively destroyed in the process and in the end tall vertical unbraced sections of both cores remained standing for a while (several seconds) until off-center deflection was sufficient to rupture the spices and/or buckle then near the base and bring them down under their own weight.

It looks like the only possibility left is that the columns failed first and it was the columns' failure that brought the buildings down. After all, it was the columns that had been holding the buildings up.

That is correct. The columns failed first in the impact and fire region. After collapse initiation floor failure would have taken the lead because the columns above mostly hit the floors below.

[Nozebro]

155. Horse pucky. Explosions evidence is the only rational explanation.

UAL 175 didn't crash into WTC 2, and this article proves it. Read it.



http://www.911research.dsl.pipex.com/ggua175/

[tenseconds]

175. where and how

Where in your kinetic calculations do you account for the pressure and speed of the mass of dust expanding and moving through lower Manhattan at such a rapid pace as well as the vaporization of water?

How can the weight of the collapsing floors be a significant increase in load to the falling upper section when the concrete turned to dust is being expelled horizontily out of the structure as well as cut core columns?

How do you account for William Rodriguez' testimony that he heard and experienced explosions on the B2 and B3 floors of WTC1 PRIOR to the impact of the plane?

How do you account for the numerous FDNY who heard a succession of explosions prior to the building's collapse?

How do you explain the evidence of core column pieces being cut at a 45 degree angle?

How do you explain the evidence of melting and sulfidization of the ends of some core column pieces?

How do you dismiss Steven E Jones' research in the examination of reconstituted molten metal from the towers that gives evidence of the use of (super)thermate?

How do you explain the phenomenon occuring just prior to the South Tower collapse where molten metal is spilling out
of the building in the immediate area of the plane's exit point, where temperatures exceeded those that would be created by a jet fuel fire are exhibited by their yellow-white hue?


source http://www.checktheevidence.com/911/Thermite2.htm

[AZCat]

177. Vaporization of water?

Where does this come in?

[rman]

76. Sure, it means that the acceleration is greater than 9m/s...

:eyes:

[vincent_vega_lives]

89. They were slowed down

but not much. Otherwise the debris falling out and then down would not have beaten the "pancake" progression to the ground.

[tenseconds]

94. explain

How do you explain the dust jets rising well above the height of the towers?

[vincent_vega_lives]

96. Most is not

Drawn down by the suction of the mass moving through the air. Some finer particles carried by the intense heat of the fire/smoke continuing upward, and displaced air from the middle of the building.

[tenseconds]

99. speed

The speed of the descending dust flurries exceeds free fall time because they were propelled by explosives.

[vincent_vega_lives]

104. That is nonsensical

In that it makes no sense. Im not talking about dust. Im talking about the large pieces of debris that is clearly ejected perpendicular from the building. They are CLEARLY NOT propelled in a downward trajectory. They STILL beat the collapse to the ground.

[tenseconds]

118. ejected

They were "ejected" by explosives.It just shows how fast they were going that initially their speed was so fast that they weren't subjected to any gravitational pull.

[vincent_vega_lives]

122. Irrelevant

Their ejection speed is irrelevant unless the initial direction is more than 90 degrees out from vertical as the acceleration due to the force of gravity is constant. None was.

Try again.

[tenseconds]

127. re: try again

The ejected dust spurts were going faster than free fall.Your model is profoundly devoid of the energy it would take to carry this off. Just the crushing of about all that was in the building minus the columns and then sending it all out in these fast moving jets of dust would have exhausted the upper floors potential energy in short notice.

Do you think William Rodriguez is a liar when he says he experienced bombs going off below him that lifted him off his feet prior to the plane's impact? Do you think NY firemen are lying when they heard explosions in the building?

[vincent_vega_lives]

133. This is like arguing with a chair

"The ejected dust spurts were going faster than free fall."

You understand don't you that unless initial trajectory is at an angle below 90 degrees from the building it has zero effect on acceleration due to gravity? Anything at or ABOVE 90 degrees would take LONGER to reach the ground...but it still beats it.

Tell me how much potential energy was stored in those buildings. It is a relatively simple equation, then get back to me.

I dont think they were lying about what they thought was happening. Mistaken is a better word.

[tenseconds]

135. listen to William Rodriguez

The dust flurries were like areas of extreme turbulence of dense particulates expanding by the heat and pressure within them.This accelerated their speed to exceed that of the gravitational pull.

If you have an equation for the amount of potential energy. Show it. Don't condescend and act like a haughty schoolmaster.All I know is and I told you this in my last post that the amount of potential energy needed to convert all that material into nanoparticles is immense. Do you have an equation for that? That is necessary also.



Have you listened to William Rodriguez yet?
http://kpfa.org/archives/index.php?show=13&month=07&year=2006 July 26 edition

[vincent_vega_lives]

136. Nice attempt

I guess you need me to school you.

PEgrav = m*g*h

PEgrav = 226,800,000kg * 9.8 m/s/s * 416m


PEg = 924,618,240,000 Joules or 924,618 MJ

1 lb TNT = 2 MJ

Each WTC towers contained potential energy equivalent to aprox 462,309 lbs or 231 TONS of TNT.

The MOAB, largest bomb in the US inventory is 21,700lbs, so figure 21 of those.

We can break it down even more...

924,618 MJ to zero in around 10 seconds, thats 9,246 MJ released every tenth-of-a-second. thats 10x 4,600 lb Bombs going off every second (averaged of course).

[tenseconds]

143. resistance

What's the force thats causing all the potential energy to be released? The upper sections. As I said before the energy from the upper sections would drastically dissipate to release the potential energy of the lower sections. You would have to calculate the gravitational energy of the top sections,calculate the loss of velocity by the top section incurred by the initial collision of the two sections, and the loss of potential energy of the top section to kinetic energy to create the masses of dust particles. The top sections aren't falling through air,they're engaging the resistance of the lower sections which carried by far the greater preponderancy of weight.

[vincent_vega_lives]

144. I asked you to calculate the PE

you refused and said that I should do it...so I did.

Your turn. :hi:

[MervinFerd]

84. So there were explosives on EVERY floor? And a detonation system that....

could set them off in the right order????

If there were only explosive near the impact sites, the remainder of the bldgs would fall 'naturally', right?

Ok.....
Enough explosive to wreck the resistance of each floor--- 100 lbs, say

X

Number of Floors----80

=

8000 pounds of explosives.

Plus the wires to each bomb and a complicated control system.
Slipped in while people were in the building.

Really clever plan.

[DoYouEverWonder]

95. I'm sure with the billions the Pentagon spends every year

on weapons systems, they could come up with something that would do the trick.

[greyl]

105. Money isn't the issue.

"they could come up with something that would do the trick."

Due to a total lack of evidence for their demolition case, CTists are forced to imagine non-existent mechanisms.

It's almost like they begin with a conclusion and twist or ignore reality to fit it. Bastions of logic, those CTists.

[DoYouEverWonder]

113. If Timmy McVeigh could do it

yet you want us to believe the US Military could never imagine how to do such a thing? Give me a break. I see you've gone to the Condi Rice School of Lame Excuses.



How hard could it be to make a bomb that looks like this on the outside? Especially when you plan to burn it up when you're done.

[greyl]

114. He couldn't do it.

Please choose between saying billions of dollars could make it possible and Tim McVeigh could have done it. Doesn't really matter anyway, because you haven't a shred of evidence for your theory. I don't even think you have a coherent theory.

[DoYouEverWonder]

116. Who do you think I am

Stephen Hawkins? Is there some unified theory of everything for the WTC? Only the OCTers would think that there is.

[greyl]

117. I try to treat everyone on message boards as if they have a 200 IQ

until they provide evidence otherwise. It's a good rule of thumb.

Who the fuck is Stephen Hawkins?

[DoYouEverWonder]

120. Hawking

It's no secret I can't type or spell sometimes.

[greyl]

121. Yeah, that's what I figured.

Who do you think I am, Tyra Banks?

[FoxOnTheRun]

126. TImmy couldn't do it

[MervinFerd]

149. Different thing altogether.

McVeigh built ONE big bomb inside a truck, then drove the truck up to the building. A lot of physical work, but not very hard really.

YOUR THEORY, as much as I can figure it out, requires HUNDREDS of explosives planted INSIDE AN OCCUPIED BUILDING. Together with a complicated detonation system. And that the -many- people necessary to design and install this thing have kept silent for 5 years.

Don't be stupid.

[FoxOnTheRun]

153. There were multiple bombs at Oklahoma and they were inside

http://www.youtube.com/watch?v=-wNXrjJkXQ4


Don't be stupid

[FoxOnTheRun]

125. What about the eyewitnesses like Rodriguez

and the fireman?

[greyl]

141. His testimony supports that people were burned, not bombed. nt

[FoxOnTheRun]

148. He said explosion

[greyl]

165. I know. However, his description fits the OCT

better than any CT, especially the part about the condition of the victims.

[Nozebro]

156. Please provide the source for your statement about "bombed".

Did you just say that because you needed a word to use other than "explosions" (which you've been told about many times) because that's a "scare" word in OCTland?

[whistle]

112. It is a really clever plan and one which demolition experts have

...studied and practiced and perfected over decades. Also, when the south tower <which collapsed first> buckled at approximately the 80th floor, the 30 floors above can be seen in all of the film clip closeup began to tip outward/sideways, then suddenly become consumed by an explosive cloud of dust and smoke, to end up exactly like the rest of the tower structure, in a heap, in small manageable pieces and debris pile at the foot print of the south tower. How did that happen? Perhaps an additional 37.5% can be added to that figure for a total of 11,000 pounds of explosives. That is a significant amount of explosives for any structure, but much closer to what experts say was sufficient when efficiently placed to bring down each WTC tower. Then there were also the seven sub-basement levels where explosions were heard and seen by witnesses and where the total integrity of the massive 47 structural steel columns could be affected by specially placed heat intensified explosives that could melt and cut thick steel columns. So another 1,000 to 2,000 pounds structural steel cutting explosives for each tower in the sub-basements could be added as well.

Check out the demolition company websites for further information on set-up and the latest in technology for controlled demolitions. The complicated control systems for sequencing demolition patterns is high state of the art and very doable. I believe also that back in September 2001, both WTC towers were only about 35% to 40% occupied by tenants, so the majority of rent-able space was in fact vacant at the time. Workers were coming and going all of the time as tenants came and went. A demolition crew of two to two and a half dozen workers could slip in and out with wires, boxes and equipment with the proper clearance forms and IDs virtually unnoticed.

[vincent_vega_lives]

137. Kinetic energy

Each building weighs aprox 250,000 tons (226,800,000kg)

if the top 20 (say 45,360,000kg) floors fell the distance of one floor at near free fall speed...

KE = (45,360,000/2) * (4.9m/s)squared

KE = 22,680,000 * 24 = 544,320,000 joules or 544 MJ or 272lbs of TNT.

[tenseconds]

145. falling one floor

The top sections of the building didn't fall at free fall speed.Free fall speed for the top section would have to be about 200mph to reach the ground in 9.2 seconds. The top section would have hit the lower section in less than a second and wouldn't have exceeded much over 20 mph.

[vincent_vega_lives]

146. Free fall is acceleration, not mph

9.8 m/s/s

20 mph = 8.8 meters/sec. I used 4.9 meters/sec. (around 11 mph)

But you could figure that...right?

[greyl]

166. Fundamental.

Huge stupid theories are believed due to a lack of knowledge of many fundamental issues.

[tenseconds]

167. close enough

A body falls through a vacuum at 32ft/s/s. The floors were how high? 13-14 ft? Somewhere in there. At that distance the upper floors could have only accelerated to around 20 mph when they hit the lower section.

[Ezlivin]

172. And the floor collapsed as one monolithic unit

The failure was complete and symmetrical.

The 47 steel cores that were damaged on several floors were not damaged throughout the rest of the tower. Yet when the floors began to fail, the core completely failed. No one can explain how this solidly built steel framework failed when it was not exposed to heat or impact.

The building was brought down by explosives. The fuel and collision were insufficient to cause this.

[tenseconds]

174. Ezlivin

Couldn't agree with you more.

Notice how all the "official" sources never have come up with an energy requirement calculation to explain what transpired.

[mogster]

179. Good post that nails the most damning evidence

It is interesting to see how quickly the debate turns away from free fall versus core resistance, and dust clouds start to obfuscate the matter ;-)

There is no explanation for this fact. The core must have been turned to soup as it fell.

[DoYouEverWonder]

180. When the walls of the buildings fall away

It appears that the insides had already been pulverized.

If you look at the rubble very little that was inside the building survived in any recognizable form, including the people, the file cabinets, the computers, even the garbage pails were gone.

The only things I've seen that were still recognizable were objects that were in the collapse zone but outside of the buildings.

What kind of weapon can achieve this result?

[mogster]

181. Multiple demolitions?

I don't know.

Here's some pics from the site just after the collapse
09/15/2001:

The split remains of the core is seen standing in the North tower.

09/18/2001:

Closeup of the scene above.

10/05/2001:

Note the perspective here - the small men standing in front of the huge core. It seems only one-fourth is left in this pic.

Here's a satelite comparison of pre and post destruction:


Sorry for the big pics ;-)