Clarifying the Collapse Time of WTC 7

Government apologists have argued that WTC 7 took 13 or more seconds to collapse, thus disproving the "virtual free fall" argument. However, this argument entirely misses the point.


Because the videos show that the penthouse collapsed long before the main building. In fact, everyone admits that there was a delay of several seconds between the collapse of the penthouse and the collapse of the rest of the building.

"An object at rest tends to stay at rest". So once the movement stopped, it should have stayed stopped.

Therefore, the collapse of the main portion of building 7 - several seconds after the collapse of the penthouse stopped - should be treated as a discrete and new event (see discussion below).

Since the main building collapsed in approximately 7 seconds - the same time as a controlled demolition takes - that is strong evidence that WTC 7 was in fact demolished.

The important comparison is the collapse time for the main portion of a building. In videos of controlled demolitions, demolition charges are often visible long before the building starts to collapse, but these should not be included in the collapse time. If there are things going on inside the building after the charges go off but before the main building visibly starts collapsing, then that should not be included in the timing calculations.

In other words, government apologists will argue that alot was going on inside WTC 7 between the end of the collapse of the penthouse and the beginning of the collapse of the main building. They have provided no evidence for that argument. Indeed, if there had been significant movement inside the building after the collapse of the penthouse, this should have resulted in some movement or deformation of the building visible from outside.

More importantly, alot might also be going on inside other buildings between the start of demolition charges and the start of the visible collapse of the main building. There is simply no way to know (there are usually not cameras inside buildings being demolished, and there were no cameras inside WTC7 to capture what was happening; so this cannot objectively be measured).

The comparison should be in the time that the main buildings take to collapse. This is an objective measurement (unlike guessing about what is going on inside of a building when no movement is observable from outside), and readily observable from video.

Note: For any previous instances of controlled demolition when a penthouse, antenna or other roof structure was demolished before the main building, then - for the sake of consistency - that must be excluded from the collapse time when comparisons are made to WTC 7.

Update: Mechanical engineer Tony Szamboti agrees with this analysis, and adds:

"The WTC 7 East penthouse had columns on its perimeter and none in its interior. On three sides these columns mounted near the edge of the roof of WTC 7. It is unlikely that a collapse of any core columns of the main building could have pulled them completely down without the roof beams breaking completely loose from the exterior columns and moving down completely also."

In other words, had the initial collapse of the penthouse been caused by a collapse of the core of the main building, then the rest of the roof would have collapsed at the same time as the penthouse. Because it didn't, this is strong evidence that the collapse of the penthouse and the collapse of the main building were wholly separate events.

Clarifying comment from Tony Szamboti

"It is unlikely that the roof beams were severed from the exterior columns, which is what would be necessary for a core collapse to cause the penthouse to collapse."

I changed the last paragraph at to reflect that comment.

The government needs new glasses.

By stating that the beginning of "collapse" was whatever internal damage that caused the penthouse to fail, they must also include the dozens of videos of admitted demolitions that are blasted 5 or 6 seconds before the actual building starts to move downward. They have nothing to say about "collapse times disproving demolitions" in this regard.

However, I have to say George, we have to stop using "Newtons Laws" as evidence of anything, in terms of physics acting within a non-inertial frame of reference. When gravity and all the internal forces of a complex structure are taken into consideration, Newton's three "Laws" of motion do not apply in their strict form. All three laws are well satisfied within the confines of the differential equations and internal force calculations that are used in the static and dynamic determinacy and kinematics of a structure. You cannot apply any one of those laws, as Newton assumed them to be, anywhere but deep space, where no amount of gravity would affect the object in question.

A good example of this, is the absurd notion that "the WTC buildings fall into the path of most resistance". Well, as Greg Jenkins so eloquently stated---and I'm paraphrasing---that path ACTUALLY, would involve the moving part of the building, flying off into space and returning back to Earth somewhere else. There was nowhere BUT down for those structures to go, considering it would have taken far more energy to push the blocks off to the side to make them fall over. IF dynamic loads were an order of magnitude beyond the yield limit of the lower structure, they would accumulate mass and go where gravity takes it... not off to the side. This is, of course, IF and ONLY IF, the lower structure---and the many mechanical floors that were considerably stronger than the typical floors---could not eventually arrest the downward-moving rubble pile.

Please understand, I am not defending the official story, nor do I believe it. However, there is a great deal of dis- and misinformation put about within our movement, that needs to be cleared up on a technical level. Instead of referencing "Newton's Laws", which are quickly ignored as arguments by real engineers, we should focus on the improbability of the actual claims of the government... which we do in spades.

It's the matter of the details, if we are to "impress the Devil".

I don't quite understand this

"IF dynamic loads were an order of magnitude beyond the yield limit of the lower structure, they would accumulate mass and go where gravity takes it... not off to the side. This is, of course, IF and ONLY IF, the lower structure---and the many mechanical floors that were considerably stronger than the typical floors---could not eventually arrest the downward-moving rubble pile."

Let's examine the case of the North Tower. In it, the lower part of the tower comprised approximately 90 percent of the mass of the building. On the other hand, pictures of the destruction show that, early in the "collapse", the upper part itself was disintegrating, ie being reduced in mass:

So, I don't think there is a question of whether the much stronger lower part should have arrested any potential collapse. Not that I believe that office fires lasting a max of 20-30 minutes in any given location could have in any way weakened the steel.

I think the many tall buildings that have TOPPLED to some side in earthquakes show how buildings follow the path of least resistance when falling. Structures fail asymmetrically, and the resulting collapse can only be asymmetric. Quite simple, really.

Ask a real engineer...

... and they will not agree with you.

The INITIATION OF COLLAPSE is the main concern and should be the majority of the arguments waged. There is NO WAY the upper block of the North Tower could have accelerated as it did, without some serious help to remove the 80+% of columns still in service.

With that said, your assertion that a total of mass of a given structure has anything at all to do with it's relative ability to resist collapse is incredulous and needs to be backed up by a serious quantitative analysis to show why mass is the lone proponent for collapse arrest.

Otherwise, perfect column-on-column impacts will still strain the SEAMS of the columns beyond their yield limit, with a 33,000 ton mass moving at about 8 m/s^2. However, if the collapse was not perfect column-on-column impacts, all kinds of crazy things could happen, which would require a serious FEA model, and there is no way we can "guess" what might or might not happen otherwise.

When you say "stronger lower part", you forget that the actual floor connections are not any different from floor-to-floor, just the column thickness itself. And from the photographs the floor connections were clearly sheered off at almost all locations. This shows massive overload, not "explosives" necessarily. The columns themselves being severed---on the other hand---might point to other things.

Whatever "booms" were heard before the towers fell, happened before the collapse, according to most eye witnesses and no video evidence (unless they've been re-soundtracked) show anything as loud as 130db explosives above the "waterfall" of collapse sound. So the initiation is what needs to be examined, since any serious engineering professional would have to admit that once that top block gets going and loses it's strain energy, there is nothing the lower parts can do, other than sheer off at their weakest points, which are the floor connections. Plus, there could have been additional charges placed to ensure totality of collapse, or they could have been set off right before initiation, and the top block just decimated the bottom part as a result. But you are not going to convince me or anybody else who seriously studies these things that the buildings HAD to be fully laced with explosives to get the job done.

Let me add... If these now known "spray-on" thermate compounds were used, they could produce a fairly silent "melty" reaction, causing the building to fall pretty easily, if they were applied in key locations. I'm sure that whatever was used, was something high-tech and didn't make as much noise as a typical demolition material would.

Be we have to remember that demolitions use gravity and the mass of the upper part of a given structure to do most of the work. Even Bazant admits the mode of progressive collapse we saw on 9/11 was pretty much the same thing as controlled demolitions... and actually stated that studying explosive demolitions would give us data for the WTC.


Initiation conditions

I have forwarded your comment to an engineer I know.

In my opinion, too, one should above all concentrate on the conditions for any kind of collapse inititation. NIST has stated that the fires lasted about 20 minutes at any given location in the buildings, which stands to reason, and a Finnish steel engineering handbook states that in a standard office fire, the temperature of a fireproofed steel support remains under 200 degrees Celsius during a 20-minute exposure (and under 300 C during a 30-minute exposure). Surely such temperatures would have no effect on construction steel?

NIST uses the assumption

NIST uses the assumption that floor failure would cause a global loss of equilibrium, because they do offer a structural tie between the core and perimeter. But they never really proved that "pulled inward" perimeter columns, caused by failing floors is even possible. They pretty much just say it.

Let me make a addendum, for the sake of the engineer in question, you are referring my statement to. Perhaps there are those who think the building could arrest and I'm NOT ruling out that possibility. But in reality, these buildings were not designed (nor are any I know of) to withstand the force of a 33,000 ton part of itself, without AT LEAST some major failure. But I could be wrong.

Also, there is a lack of deceleration of the upper block, and is true with WTC7, and smooth acceleration is observed. So, if these upper portions overloaded a static portion to the degree is assumed, why is there no deceleration observed? Tony Szamboti calls it "Wham!". No "Wham", no dynamic overload.

This is why the "thermate" hypothesis is still valid. If portions of the structures were compromised from such material, there would be no overload, just lots of collisions, smoothly flowing downward.

The whole NIST hypothesis of "fire" causing these events is so far from reality, I'm very shocked as many people cite NIST as they do. Maybe they are scared that their own common sense is causing major cognitive dissonance... I don't know.

Mr. Kazi, please see the following:

In addition to mechanical engineer Tony Szamboti agreeing with my analysis, you might want to read what these folks have to say:

  • Kamal S. Obeid, structural engineer, with a masters degree in Engineering from UC Berkeley, of Fremont, California, says:
"Photos of the steel, evidence about how the buildings collapsed, the unexplainable collapse of WTC 7, evidence of thermite in the debris as well as several other red flags, are quite troubling indications of well planned and controlled demolition"
  • Ronald H. Brookman, structural engineer, with a masters degree in Engineering from UC Davis, of Novato California, writes:
"Why would all 47 stories of WTC 7 fall straight down to the ground in about seven seconds... ? It was not struck by any aircraft or engulfed in any fire. An independent investigation is justified for all three collapses including the surviving steel samples and the composition of the dust."
  • Graham John Inman, structural engineer, of London, England, points out:
"WTC 7 Building could not have collapsed as a result of internal fire and external debris. NO plane hit this building. This is the only case of a steel frame building collapsing through fire in the world. The fire on this building was small & localized therefore what is the cause?"


... I'm trying to figure out what part of what I said to correct a few of your points, goes against the points you made above.

Everything you just posted I agree with.

What aspects of my critique are you arguing?

I agree the twin towers and WTC7 were demolished on purpose. But stating that "the laws of physics don't add up" is too simplified to be "convincing" for a rigorous analysis of the events in question.

When I talk about the

When I talk about the falling buildings I say they fell at "nearly" free fall speed. That's plenty fast enough to make a doubter wonder about the truth of the official story.

This debates are useless

I don't want to look arrogant, but even if the penthouse would fall 10 minutes before the perimeter walls, it would change absolutely nothing on the fact, that the perimeter walls proovingly falled at free fall speed - which is - given the basics of the basic facts about the construction and material of WTC7 perimeter walls - utterly physically impossible (without a massive help of external cause e.g. explosives). NIST report is a utter criminal nonsense intended for cover-up from the very beginning - even all the money thrown from window would fall slower than WTC7 did. Period. Debate is long time ago over and who continues with it is a moron or has an agenda. Lump it folks, it's college physics.


The penthouse argument is bunk.

Here is the "Landmark Tower" demolition:

Notice two things: The building does not begin to move downward until about 10 seconds after the blasting begins.

Also, notice how loud the blasts are. Personally, I think something else besides "bombs" were used on 9/11.


The thunder sound of high-explosives is due to hypersonic speeds of their burning. But (hypothesis) if they would use nanothermite, which could burn at 50+ m/s (which is subsonic speed without the breaking-of-sound-barrier-thunder-sound of explosion) - they could just drill a hole in the box columns and pour it in, or fasten it to any other shape of the beams - it would be enough just to do it at the lower floors - then 1. there would be no thunder sound 2. the beams would literally melt or evaporate instantly after ignition of the nanothermite - which would very quickly (in fractions of seconds) burn out at 4500+ C -way above boiling point of steel - and creating the very hot pyroclastic cloud (enough to ignite cars) with the debris of then crushed concrete of the floor panels and make the debris pile very hot (consistent with the abundant iron spherules found in the dust and the behaviour of the dust clouds and the debris pile), 3. the upper part of the building would start to move exactly at freefall speed, (consistent with what is seen on the videos) 4. after falling several floors down without any resistance the relatively compact rest of the building would have enough momentum to completely crush itself against the ground, or at this point you can anyway without problem use the high explosives, because the noise of the destruction would be anyway so loud that the high-explosives charges explosions would merge with the rumble.

This scenario would be largely consistent with what we!ve seen on the videos. The nanothermite would not ignite due to any ordinary fire anywhere in the building, because the ignition point of it is way above any possible temperature of the ordinary fire. If you would use the professional electric-magnesium fuses for thermite this would be quite reliable way how to bring down the building eaxactly as we've seen it on the TV.

I agree with most of that...

...except these points:

"3. the upper part of the building would start to move exactly at freefall speed, (consistent with what is seen on the videos)"

I wouldn't say exactly. Most pixel/time analyzes show about a 7.5-8 m/s^2 decent. This detail doesn't really matter, though because such acceleration is only possible, if the majority of the perimeter columns (never mind the core) give way to allow the block to descend. Very distinctive failure lines (see here: are seen exactly in the spots where the block begins to fail (the seat of failure as it were), that are difficult to explain, other than something cutting them.

"the noise of the destruction would be anyway so loud that the high-explosives charges explosions would merge with the rumble."

I'm just not sure we have enough data about the sound pressure levels of the collapse event, to make such an assertion. If the collapse exceeded about 130 db, it's possible. But there are many videos, not too far from the collapse, that don't seem that loud to me. Opinions just don't cut it. We need more data about how loud these events truly were, and I have no idea how to attain such data.


I was talking exclusively about WTC7 (not WTC1 or WTC2). The WTC7 - according to measurements in the 911 Eyewitness 3 (8:23 and folowing) the upper 100m of WTC7 falled almost exactly at the freefall speed (maybe even faster).

Also there were really very loud explosions heard over Hudson derived by analysis ( at 1:20 and folowing) from Rick Siegel footage before and during the WTC7 "collapse" - so maybe even vast ammounts of ordinary high-eplosives were anyway used in WTC7. (The same could be found examining the video of WTC1 in the previous part of the 911 Eyewitness video)

- the towers - when I touched this - even it is OT - could be (hypothesis) easily brought down exactly in the manner of what we've seen on the videos just if there would be 1. drilled holes (there were service holes anyway) into the core box columns in the basement, the nanothermate poured in, 3. ignited by electric-magnesium fuses, melting sections of several lower floors core steel structure (comprised of box collumns only) instantly in fractions of seconds (I estimate it would last not more than ~0,1 seconds, making a sound of fuzzy subsonic explosion, and the bearing function of the core would be thoroughly gone throughout several floors) 4. the tremendous weight of the core rest literally hanging on the rest of the structure, without virtually anything visible from outside of the building, then transfered through hat truss at the top of the building would compromise the perimeter wall exactly at the weakpoint where it was previously compromised by the explosions (plane impact) 5. the upper structure would start to move pulled straight down and crush the structure below and attaining momentum, then the high explosives wave of high explosives charges at the rest of the core would crush the rest, including the floor panels which were made of unarmed! concrete - so would be crushed to the dust just due to hi-explosives shockwaves, which would transfer thorugh floor panels steel support at the speed of sound in steel (~6000 m/s) (-so the concrete, which has lower speed of sound constant than steel, would be crushed later than the wave would reach the outer columns with undiminished intensity) and shred the perimeter exactly in the place of weakpoints of joints and welds (no charges at the perimeter needed) and eject their members outwards. So many charges at core would be only long ininterupted rumble.
I estimate several tons of RDX for one building, mounted inside the elevator shafts +several tons of nanothermite poured into the core box columns would be enough. I think the team of 10 people would be able to prepare whole building to demolition this way - if weli organized - overnight - using something as just one truckload of explosives+nanothermite+fuses+electronic timers!!!
Such a scenario would be largely consistent with what was seen on the videos and photographs and with the witness accounts.

Something about nanothermites and their tremendous effectivity here (even it is about the Al-MoO3 nanothermites - the effect of them would be rank-comparable to Al-Fe2O3 one - whose signature was found in the WTC dust)>

I don't assert categorically there was surely the thermite used, but from the samples of the dust, aftermath high pile temperature, presence of the typical pyroclastic flow and reported presence of the molten steel below the rubble - it would look extremely probable and feasible way to achieve the demolition of WTC7 as was seen on the videos. Moreover the realisation of the whole operation would need to involve far less people, than using any other methodics. The speed of the whole event would virtually exclude any possibility the building was brought down without a large external cause of its failure, moreover the speed, which seems to be even below the free fall speed in air would suggest use of high explosives located close above the floor panels - which would be only feasible (and also the simplest one) way which could accelerate the speed of the failure beyond the theoretical freefall speed. No external directed energy could possibly contribute to this, not speaking about that there are no even theoreticaly known DEW (which some dezinformators suggest), which would be capable to cause such an abrupt and generalized failure without visible signs - as very bright flashes of evaporating and in flames bursting parts of the building. So the Occam razor would firmly chose the conventional high-explosives or high-explosives+termite cause of the buiding failure, excluding both the gravitational collapse or use of DEW beyond feasible and probable posibility being the cause of the WTC7 building failure. Period.