Understanding the claim of "The top of the north tower fell at 65% or 2/3 of g"

Mendel

Senior Member.
?!?!?!?

"they aren't in free fall *because* there's resistance""

I even *emphasised* the "because". Clearly, resistance is the cause of the non-free-falling.
Yes.

What is the resistance with the see-saw?
What is the resistance in the one-end-supported falling lever?

FatPhil

Senior Member.
Yes.

But you seem to claim the reverse—that anything not in free fall has resistance.
A—>B is not the same as B—>A.

Wikipedia: "In Newtonian physics, free fall is any motion of a body where gravity is the only force acting upon it." No mention of resistance.

Which definition of free fall are you using that involves resistance?

The definition which mentions that resistence must be absent, such as the one you quote. That's what "only" means. Everything else is excluded. No other forces are admissible. Resistance is a force. Therefore it's inadmissible.

econ41

Senior Member
?!?!?!?

"they aren't in free fall *because* there's resistance""

I even *emphasised* the "because". Clearly, resistance is the cause of the non-free-falling.
By definition????

BTW There is an additional complication that sometimes arises. e.g. in the Chandler v NIST contention over WTC7. Free Fall Acceleration ["FFA"] does NOT prove the body was in the state of Free Fall ["FF"]. It is not relevant in the current discussion but "FFA proves FF" is a common false premise assumption relied on by truthers. Similar to the other truther false premise "FF proves CD". It doesn't. Then throw in the routine confusion/conflation of FF and FFA....

FatPhil

Senior Member.
Yes.

What is the resistance with the see-saw?
What is the resistance in the one-end-supported falling lever?

I assert that A1 causes B where A1 was relevant to the original question. You show me a situation where A2 causes B where A2 is not relevant. At no point have I argued that A1 is A2, you're straw-manning me. And I haven't said A2 doesn't cause B either, quite the opposite. I do not recognise the stances that you appear to be attributing to me.

econ41

Senior Member
"Free Fall" is the state where a body (or discrete closed sub-system for the pedants ) is not acted on by any forces other than gravity.

Free Fall Acceleration will result from a state of Free Fall. BUT it can also result from where a body is acted on by forces other than gravity AND those forces sum to a net zero. Whilst the contentious WTC7 bit of FF or FFA probably went over "g" - which means it could NOT be free fall - because there was some non-net-zero force acting other than gravity.

FatPhil

Senior Member.
"Free Fall" is the state where a body (or discrete closed sub-system for the pedants ) is not acted on by any forces other than gravity.

Free Fall Acceleration will result from a state of Free Fall. BUT it can also result from where a body is acted on by forces other than gravity AND those forces sum to a net zero. Whilst the contentious WTC7 bit of FF or FFA probably went over "g" - which means it could NOT be free fall - because there was some non-net-zero force acting other than gravity.

Exactly. And this is where @Mendel's see-saw is helpful. Some bit of a sufficiently-long see-saw will be accelerating at exactly g as it lowers, simply because the far end will be higher than g and the fulcrum will be zero, and it's a continuous function, so there must be, at any instant in time, a point where it's exactly g. (I wouldn't be surprised if that point moves over time, I've not done the maths.) But it's definitely not in free fall.

econ41

Senior Member
Exactly. And this is where @Mendel's see-saw is helpful.
The child of the low side is not in free fall because of the resistance applied to his arse by the see-saw plank - counterweighted by the kid on the other end.
Some bit of a sufficiently-long see-saw will be accelerating at exactly g as it lowers, simply because the far end will be higher than g and the fulcrum will be zero, and it's a continuous function, so there must be, at any instant in time, a point where it's exactly g. (I wouldn't be surprised if that point moves over time, I've not done the maths.) But it's definitely not in free fall.
I've had fun over the years posting challenges about "Free Body Physics" especially WRT "over G". Here is one example - if you haven't seen it before: https://www.metabunk.org/threads/acceleration-greater-than-g.5635/#post-143011

Oystein

Senior Member
Thanks econ41, much appreciated.

I never understood how truthers came to the conclusion that 65% (or 2/3) of g meant zero resistance. Which to them meant columns removed by explosives.
I don't know if the following is something any Truthers claim, but here is a conceivable mechanism to solve your confusion:

Suppose the collapse is initiated by blowing out / making disappear by magic all columns (12 feet of column lengths) between two floors. The top then falls in free fall (ignoring resistance by 63x63 meters of slab pushing down on and out of the way ll that air below).
Then, juuuuuuuuust before the next floor is hit, again all columns (12 feet of them) are magically removed, such that the falling top hits a floor slab that is stationary, but without any vertical support.
And so forth.

Because the falling mass hits a floors slab every 12 feet that is (almost) stationary, and that slab has considerable mass, a momentum transfer will occur, within a very short time interval, where the single slab is greatly accelerated, and the falling top somewhat decelerated - before the whole mass continues in free fall.

This model would actually converge on a net acceleration of (and here I am blowing a secret) 1/3 of g (not 2/3!). But start out near g, and decrease as more and more floor slabs are consumed per second.

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HOWEVER, for that to happen, it's not actually necessary to blow out vertical supports, and to blow out vertical support, you don't need to blow out columns!

Because most of the falling mass hits floor slabs, very little hits columns. The loads on the slabs is transferred to columns via floor truss seats, so all it takes is to blow out those seats.

And in reality, it didn't require any demolition to shear off the truss seats, nor would the shearing (necessarily) cause a deceleration in addition to the momentum transfer that happens anyway:
Momentum transfer in an inelastic collision - and these collisions are largely inelastic - always results in a decrease of Kinetic Energy (KE), and that KE will flow - into "destruction" - breaking, inelastic deformation, also a bit heat. That energy lost upon each collision is far more than what is needed to shear off the truss seats. And so they are sheared off (or some spot in the load path that is even weaker), without requiring any additional transformation of KE to destruction.
Therein lies one of the main thinking errors in Chandler's and Szamboti's and many a Truther's heads: They don't appreciate that the 1/3 or 2/3 of Potential Energy released by the mass simply going down is more than sufficient to bend, break, tear out the weakest elements in the load paths supporting the horizontal elements most affected by the avalanche of mass.

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B&Z original, September 2001 argument was that even in the only theoretically conceivable event that no weaker load path than fully braced, perfectly vertical, undamaged columns were available, crushing them would eat up less energy than is available from gravity alone.
it turns out that they had their numbers somewhat wrong, and that substituting for better numbers would move their conclusions more into "undecided" territory.
But as @econ41 never tires of pointing out, any model that builds on "column crush" is a wrong model to describe the reality of the WTC collapses.

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Now as for the supposed "smoothness" of the acceleration curve and the lack of a "jolt", I think most counter-arguments have probably been mentioned in this thread already (I didn't read all of it), but here is my summary:
1. Their data is smoothed simply by choosing to sample at a low rate, i.e. only 6th frame (1 data point per 0.2 s in Chandler's video) and computing averages over those. Any jolt that might be there is thus mathematically certain to get smoothed out, possibly beyond recognition. If you look at the raw data, of course it is full of jolts. These Truthers say that raw data is too noisy, due to measurement error, and that is certainly true. BUT that means that, absent a robust error analysis, and possibly even with a robust error analysis, it may not be possible to decide either way if there is a jolt or not.
2. They measure points on or near the roofline (antenna?). There is a lot elastic and complex structure between those points and the "crush" interface where jolts would actually occur, and so any real jolts will get significantly attenuated, if not entirely smoothed out, by the action of said intervening structure.
3. The tops of both twin towers tilted significantly before they descended as a unit. This alone ensures that there would not be a single jolt affecting the entire top structure - the only case where measuring the downward motion of a single point on the periphery would have any chance of being representative for the whole. Instead, each column would feel some resistance (if only that from truss seats as they are being sheared off) at its own point in time - there'd be many local "jolts" somewhere during every measurable time interval (video frame length).
3b. Showing the jolt at one Verinage demolition misses two important differences: a) That demolition is DESIGNED to have the top go down horizontally, evenly, without tilt, in order to maximize the force at which the structure below gets hit when it gets hit. It is DESIGNED for columns to hit columns (because they actually want to crush them; b) this was a concrete structure with concrete columns and concrete beams - which is probably why the demolition was planned that way: They wanted to maximize the amount of concrete that gets crushed by gravity.

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Chandler's tracking point and plot, at around 55 s into the video already refered to above, suffers from several more problems

1. The wall, the roofline of which serves as Chandler's target, is toppling towards the camera position, so there is some rotation in addition to linear descent. Because the wall starts out vertical, the trajectory of the target point due to rotation toward the camera, which is located lower, would make it look like moving up, when in fact it starts to come down.
Later, as the wall leans seriously, the rotation may increase the apparant velocity (and acceleration) of the observed point. Although the rotation itself surely decreases later into the descent, which makes matters even more complicated - Chandler considers none of this
2. The straight line he plots through his 17 or 18 chosen data points does not fairly represent acceleration throughout those 3.4 seconds - but he pretends it does. He claims explicitly that the onset of fall is "sudden", that the 2/3 of g are there right from the beginning. But quite obviously, you can draw a straight line to best approximate the first 5 data points, and it would be considerably less steep, representing a lower acceleration. Similarly, you could draw a stright line through his last 4 data points, and get a higher acceleration. So this would make it look as if acceleration is actually increasing over time. (It probably isn't - this may be more an artifact of the rotation I discussed above)
3. As already pointed out, he does not differentiate between collapse stages - initiation (top starts to lean...), transition (all columns get severed over a brief interval) and vertical progression ("crush" throughout entire cross section), which are governed by different processes. If the collapse were initiated by blowing out all vertical supports, he'd have seen instant acceleration near g (and little to no rotation), but instead, during the first 0.8 seconds or so, according to Chandler's plot, "resistance" is the highest. This could be consistent with a lot of columns still having connection, and there being only tilt. Then the top releases - acceleration goes up; it appears to vary (go up and down) even in Chandler's data due to chaos - it is not actually smooth, despite his choice of rather long time intervals.

Oystein

Senior Member
I think one error of thinking that many Truthers commit is this:

To assume that any intact vertical support, when hit by a falling mass, would exert a "resiatance" (upward force) of at least, and actually more, than the weight (static gravitational force) of that same mass, because the vertical supports were able, obviously, to exert exactly the opposite force up of the weight weighing down on them, and then some. And that therefore, there would have to be a net deceleration absent any additional means to reduce vertical capacity, i.e. demolition devices. As if NO structure could ever collapse completely from a local failure.

There are two way to debunk this nonsense:

A) The easy way: By showing a structure that collapses completely under gravity following a local failure - any structure will do, like a Jenga tower or Mike's earlier garage model with wood sticks and magnets. To prove something is possible in general, it suffices to demonstrate one example.

B) The harder way: by pointing out how structural supports actually work: They respond to a weight (load) by deforming elastically. As long as the elastic strain limit is not exceeded, they can continue bearing the same, static load for hundreds of years, constantly. However, the same mass, applied dynamically, exerts a downward force at least twice as big as the static weight, and generally more than that - and that this may easily exceed the elastic strain limit, and then the support deforms, and loses its capacity, and fails; and once it fails, it can no longer bear any weight, not even statically. In a progressive collapse of a building, the important thing to understand is that, as the falling mass deforms the structure below, it needs to descend only a few inches to render the support void, and then it can continue for several feet entirely unimpeded. The resulting NET acceleration (down) can be positive, because all of the mass meets no resistance most of the way down, and a (even if pretty high) resistance for only a small portion of the way. This is true even in the theoretical "column crush" model of B&Z 2001: Each crushed column resists along a shorter distance than it fails to resist.

Oystein

Senior Member
Do you acknowledge this is just a personal theory of yours, right? I don't think NIST for example comments at all on whether or not the falling material missed the columns.
In NIST's FAQ, there is one item on the question of why total collapse was inevitable, explaining why the floor slabs would necessarily fail once hit by a mass of at least 6 floor slabs coming down on them - because it's the truss seats that fail, not the columns, and the truss seats, in total, could at most bear a dynamic loading of 6 floor slabs. So this at least implies that "missing the columns" was a significant driver of collapse progression.

Also, somewhere in the Annexes, they show plenty of truss seats having been bent or sheared up or down, depending on whether they were on floors above or below the initial failing floor. Again, that suggests awareness that collapse progressed by shearing slabs from columns, not by columns crushing.

I think we can be pretty certain that NIST was also aware that almost all recovered and documented columns were still in one piece, hardly bent and certainly not crushed. Any cursory glance at any source of images of columns post-collapse would reveal that fact. There are a few "iconic" columns (or beams) bent in dramatic curves - but clearly they represent outliers.

That is one of the HUGE problems for the "demolition" theories: The huge number of generally intact wall panels and core columns that were obviously NOT blasted to smithereens. In particular any theory that claims that ALL or most columns were cut MULTIPLE times to allow for the collapse to progress without deceleration or jolt has to fend with the obvious lack of ANY evidence for any columns thus severed, when it actually demands there must be THOUSANDS (240 or so perimeter columns, 47 core columns, if blasted and cut on every floor from the 90th down, that would make for more than 4000 cuts to some 1500 column section, and ZERO wall panels surviving as a whole. If you posit that columns were severed only at the splices, that would still leave you with the problem to explain that Truthers cannot point to a single column or panel with blast marks at the splices. Truthers point to the rapid ejection of dust along horizontal levels as the towers came down - but miss the fact that the wall panels were staggered - the "blast waves" either would have to be staggered as well, which they aren't, or 2/3 of all wall panels (i.e. some 1,500 panels) would have to have been cut at 1/3 of their length, but ZERO actually were).

econ41

Senior Member
But as @econ41 never tires of pointing out, any model that builds on "column crush" is a wrong model to describe the reality of the WTC collapses.
I'm pleased that you noticed . But, fun aside:

That single issue - failing to recognise that the falling material "missed" the columns - has been the #1 cause of confusion over the full history of Twin Towers debate.

And my own personal preference in discussion, analysis and explanation, is to focus on fatal errors in the "big picture" because errors at that level of the taxonomy are almost always fatal to more detailed discussion. (And I won't mention my other "hobby horse" - something about "cannot prove a global negative" in one specific scenario.)

econ41

Senior Member
(I wouldn't be surprised if that point moves over time, I've not done the maths.) But it's definitely not in free fall.
And it could cause an occurrence of Free Fall Acceleration AND still would not be Free Fall. << And that comment should separate those who know their physics from those who are copy-pasting some third party.

econ41

Senior Member
Just a belated suggestion to possibly clarify a couple of minor issues:
Are the kids on a see-saw falling at less than 1 g because of resistance?
Yes. As far as the kid on the descending side is involved the resistance comes from the force between his arse** and the see-saw plank. The plank would have to descend at greater than "g" to leave the kid behind in BOTH the state of "Free Fall" and moving with Free Fall Acceleration.
,
** Excuse "arse" = I don't use "ass" other than in reference to equus asinus and my preferred "bum" probably does not survive across cultural barriers.
Or is it because they're not actually in free fall?

Agreed. Neither Free Fall nor Free Fall Acceleration.
If you support one end of a lever on a fulcrum and let the free end fall, different parts of the lever will accelerate at different rates (some exceed 1g, some don't),
Agreed
although there is no resistance.
It depends how you define the system/sub-system under discussion.

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Mendel

Senior Member.
Suppose the collapse is initiated by blowing out / making disappear by magic all columns (12 feet of column lengths) between two floors. The top then falls in free fall (ignoring resistance by 63x63 meters of slab pushing down on and out of the way ll that air below).
Then, juuuuuuuuust before the next floor is hit, again all columns (12 feet of them) are magically removed, such that the falling top hits a floor slab that is stationary, but without any vertical support.
And so forth.

Because the falling mass hits a floors slab every 12 feet that is (almost) stationary, and that slab has considerable mass, a momentum transfer will occur,
Trying a gif of a "Newton's cradle" (CC BY-SA 3.0 Dominique Toussaint):

If the slabs in your hypothetical experiment have equal mass, then they simply exchange momentum when they collide. The result is functionally the same as if you had dropped each slab separately, with the lower slabs being dropped later. That means the acceleration of each slab is 1 g while it drops, but if you average the acceleration over time starting with the first slab dropping, you get a lot of weighted averages of 0 g and 1 g to add up to a net system acceleration that has to be markedly lower than 1 g.

It's thefefore unreasonable to expect 1 g in a progressive collapse that starts at the top.

If you start the collapse at the bottom, everything above starts falling at the same time, so the net acceleration is closer to 1 g (no averages with 0 g).

Mendel

Senior Member.
It depends how you define the system/sub-system under discussion.
Like I said, terminology.

I'd have said that the motion of the one-sided lever is constrained by the fulcrum, but there's no resistance; but obviously the fulcrum exerts a force opposite gravity, which is therefore a resistive force.

The net acceleration of the lever depends on the rotational inertia (and possibly torque) of the lever.

Oystein

Senior Member
Trying a gif of a "Newton's cradle" (CC BY-SA 3.0 Dominique Toussaint):
...

If the slabs in your hypothetical experiment have equal mass, then they simply exchange momentum when they collide.
No.

In a Newton's cradle, you have as nearly as possible elastic collisions, which fully conserve (more precisely: return to the system once elastic strain is released) kinetic energy in addition to momentum.
But when you have a huge part of a building crushing into another huge part of the building, lots of inelastic deformations take place, and indeed these collisions are mostly inelastic. This reduces for good the kinetic energy, and thus the velocity of the system and its acceleration.

Abdullah

Active Member
This is actually quite ironic. The argument here is that the sudden, symmetric collision with each successive floor should have caused a brief jerk (technical term: change in acceleration (I'm trying to steelman the truthers)). The response is of course that the collapse was not perfectly symmetric.

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I see this statement from time to time, but most recently posted by Henkka:

I'm trying to understand how a falling object, with no resistance and being affected only by gravity, can only fall at 65% or 2/3 of g? Doesn't this mean that there is resistance of some kind that is keeping the object from falling at freefall?

Would someone kindly explain? What am I missing?

2/3 of G is not G so there was resistance which disproves the demolition theory. There is no evidence of demolition and never will be because it didn't happen.

Jeffrey Orling

Senior Member
G or a fraction of it has nothing to do with demolition

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G or a fraction of it has nothing to do with demolition
It absolutely does disprove demolition.

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Gamolon

Active Member
G or a fraction of it has nothing to do with demolition
It does when truthers claim that all support was cut simultaneously (zero resistance) with explosives/thermite, below the descending section.

econ41

Senior Member
@ParadoxicalKat -- welcome to the forum.

Two of your assertions are correct:
2/3 of G is not G so there was resistance
Yes. And:

demolition ...... didn't happen.
Also "true". (Strictly it is the extant hypothesis that has not been falsified if we are rigorous in applying the "scientific method")

You will find that some of us long-term members like me can be pedantic about your other two claims. Viz:
...which disproves the demolition theory.
It does count against some forms of CD but is not globally correct. Free fall does not "prove" CD > a topic for further explanation. And:
There is no evidence of demolition...
There is no distinguishing evidence. i.e. evidence that "proves" CD and "disproves" other forms of collapse. For example, the oft-quoted truther mantra - "falling in own footprint" is a feature of a collapse mechanism. Not what started the collapse. CD is a starting trigger. Both "free fall" and "own footprint" are features of the collapse mechanism. Not what started the collapse. Another topic for further discussion.

FatPhil

Senior Member.
2/3 of G is not G so there was resistance which disproves the demolition theory. There is no evidence of demolition and never will be because it didn't happen.

If any part of a building above the point of controlled demolition crushes or crumples (which is the sina qua non of demolitions) it implies there was an upward force upon it to crush or crumple it. And if there's an upward force on the un-demolished part of the building, it's not in freefall. So, unless there's a balancing downward force (which would be an extraordinary claim that would require extraordinary evidence), or a rotation (which clearly won't act equally across the whole interface of collapse, and thus does not help your argument), the part of the building will not be accelerating downward at g.

=> your "not G ... disproves the demolition theory" deduction is false.

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@ParadoxicalKat -- welcome to the forum.

Two of your assertions are correct:

Yes. And:

Also "true". (Strictly it is the extant hypothesis that has not been falsified if we are rigorous in applying the "scientific method")

You will find that some of us long-term members like me can be pedantic about your other two claims. Viz:

It does count against some forms of CD but is not globally correct. Free fall does not "prove" CD > a topic for further explanation. And:

There is no distinguishing evidence. i.e. evidence that "proves" CD and "disproves" other forms of collapse. For example, the oft-quoted truther mantra - "falling in own footprint" is a feature of a collapse mechanism. Not what started the collapse. CD is a starting trigger. Both "free fall" and "own footprint" are features of the collapse mechanism. Not what started the collapse. Another topic for further discussion.

Correct, witnesses do not qualify as evidence.

FatPhil

Senior Member.
Correct, witnesses do not qualify as evidence.

Legally, witness testimony *does* count as evidence, but it's not considered to be the same type of evidence as physical evidence or documentary evidence.

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Legally, witness testimony *does* count as evidence, but it's not considered to be the same type of evidence as physical evidence or documentary evidence.
It doesnt matter how many witnesses there are or what they say, it will never be evidence for demolition. It is impossible for eyewitness testimony to be considered evidence for demolition.

FatPhil

Senior Member.
It doesnt matter how many witnesses there are or what they say, it will never be evidence for demolition. It is impossible for eyewitness testimony to be considered evidence for demolition.

My rebuttal of that statement is identical to the prior rebuttal you are responding to. There's no point in going round in loops.

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My rebuttal of that statement is identical to the prior rebuttal you are responding to. There's no point in going round in loops.
Then forgive me for dragging this on but that would mean you are arguing eyewitness testimony can qualify as evidence for controlled demolition and I am disagreeing with you, it cannot qualify as evidence for demolition no matter the context. There is 0 evidence for demolition, if witnesses could count as evidence for demolition then there would be evidence for demolition but there isn't because they can't.

Henkka

Active Member
2/3 of G is not G so there was resistance which disproves the demolition theory. There is no evidence of demolition and never will be because it didn't happen.
If 2/3 of G disproves demolition, what does, uh, 3/3 of G prove?

econ41

Senior Member
Then forgive me for dragging this on but that would mean you are arguing eyewitness testimony can qualify as evidence for controlled demolition and I am disagreeing with you, it cannot qualify as evidence for demolition no matter the context. There is 0 evidence for demolition, if witnesses could count as evidence for demolition then there would be evidence for demolition but there isn't because they can't.
Let's take these points oneat a time. Recall that you said:
Correct, witnesses do not qualify as evidence.
Step #1 the witnesses are not evidence. Their testimony could be evidence. Subject to "rules" as to what evidence is acceptable to the tribunal. In the legal domain, the relevant one is "admissibility" and there are equivalents in scientific discourse.

Step #2 - the first issue you raise in your latest post:
" ...that would mean you are arguing eyewitness testimony can qualify as evidence for controlled demolition..."
That is the correct situation as both @FatPhil and I have said.

"...I am disagreeing with you, it cannot qualify as evidence for demolition no matter the context."
Is wrong. It is "begging the question" as one major flaw. Presuming "there was no demolition" when the question being tested by evidence is "was there demolition"?

And the remainder of your post repeats the circular error of presumption.

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If 2/3 of G disproves demolition, what does, uh, 3/3 of G prove?
It proves that the dynamic load of the structure overwhelmed the integrity of the building resulting in a <1% resistance diametric parameter.

Step #2 - the first issue you raise in your latest post:
" ...that would mean you are arguing eyewitness testimony can qualify as evidence for controlled demolition..."
That is the correct situation as both @FatPhil and I have said.
You will have to support your claim with evidence/citations from reputable sources.

econ41

Senior Member
It proves that the dynamic load of the structure overwhelmed the integrity of the building resulting in a <1% resistance diametric parameter.

You will have to support your claim with evidence/citations from reputable sources.
Let's not argue "Burden of Proof". The #1 problem with your claim is that the argument is a circular presumption. Begging the question.

Do you really not understand why your argument is circular? Begging the question?

Henkka

Active Member
It proves that the dynamic load of the structure overwhelmed the integrity of the building resulting in a <1% resistance diametric parameter.
How would the weight of a building ”overwhelm” the structure designed to hold it up, and that had done so for decades? We’re not talking about an anvil crushing a feather here.

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Let's not argue "Burden of Proof". The #1 problem with your claim is that the argument is a circular presumption. Begging the question.

Do you really not understand why your argument is circular? Begging the question?
I believe the part of my post that you're referring to as circular is this.
"if witnesses could count as evidence for demolition then there would be evidence for demolition but there isn't because they can't."
And while I can see how that may be considered circular, that isn't my argument. All I'm saying is that witness testimony cannot be considered evidence for demolition, or at least no reputable source shows that. I'm also saying that there is no evidence of any kind for demolition, I think we can all agree on that.

How would the weight of a building ”overwhelm” the structure designed to hold it up, and that had done so for decades? We’re not talking about an anvil crushing a feather here.
Because it was designed to support a static load, not a dynamic one. On top of this the weight of the upper portion of collapsing building would be compounded with the weight of the floors it's destroying and could accelerate at a rate indistinguishable from gravity. All of this is hypothetical though because it didn't collapse at the rate of gravity for any portion of the collapse.

econ41

Senior Member
All I'm saying is that witness testimony cannot be considered evidence for demolition, or at least no reputable source shows that.
Take care. You are conflating two different aspects:
(1) The admissibility and relative "strength" of evidence. AND

(2) Whether or not the issue in contention is accepted as true or false.

For example there is witness testimony of "loud banging noises" during the WTC collapse events. That is valid evidence. Some witnesses attribute those noises to "explosions". Also valid evidence. Even fewer witnesses attribute the noises to the use of steel-cutting explosives. Also valid evidence. BUT all the available evidence should THEN be "weighted" by the assessor of fact and the overall assessment - the "accepted" or "extant" hypotheses conclude "No case for CD". That does not exclude the witness evidence from consideration. But it is outweighed when assessed in the context of all evidence. The evidence for "No CD" is far stronger than the evidence for "CD". That does not make the evidence invalid. Merely outweighed by other evidence.

I'm also saying that there is no evidence of any kind for demolition,
And I'm saying you are wrong. The falling at 2/3rds "g" is evidence for CD But it is also consistent with "No CD" so, as I said in my first post to you:
"There is no distinguishing evidence. i.e. evidence that "proves" CD and "disproves" other forms of collapse.
The evidence supports both sides. Therefore it adds nothing to the "proof" either way. But that does not mean that it is not evidence.
I think we can all agree on that.

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(1) The admissibility and relative "strength" of evidence. AND

(2) Whether or not the issue in contention is accepted as true or false.
(1) Even if it is admissible as testimony, it's still not evidence for demolition. It's evidence that someone claims to have experienced something, not evidence that it happened. It cannot qualify as evidence for demolition whether weak or strong.
(2) The issue in contention is "is there evidence for demolition" and this is accepted by the scientific community as false.

For example there is witness testimony of "loud banging noises" during the WTC collapse events. That is valid evidence. Some witnesses attribute those noises to "explosions". Also valid evidence.
That is valid evidence that they think they heard loud banging and they think they heard explosions.

Even fewer witnesses attribute the noises to the use of steel-cutting explosives.
What they attribute it to is NOT evidence. Their testimony is what they claim to have experienced, not what they think it might have been. Explosion can be interpreted a number of ways. Even if they said "I saw them setting up explosives and I saw the explosives detonate and I saw them push the detonator", none of that would be evidence for demolition.

That does not exclude the witness evidence from consideration.
That is where you're wrong, it is excluded from consideration for demolition.

The evidence for "No CD" is far stronger than the evidence for "CD".
The evidence for "No CD" is the complete and total lack of evidence for CD. If the witness testimony counted as evidence for CD(it doesnt) then there would not be "no case for CD".

The available body of evidence does not necessarily contradict CD, CD simply lacks the evidence necessary for consideration. That is why NIST did not pursue CD, there was no evidence to support it. If witness testimony could be considered evidence for CD then NIST would have investigated CD. You may call that circular reasoning but I call it critical thinking and rational thought, Eric Conley.

econ41

Senior Member
(1) Even if it is admissible as testimony, it's still not evidence for demolition.
Self rebutting. It is admitted as evidence in the form of testimony. Which is a weaker form of evidence than (a) Evidence of physical objects; OR (b) Evidence of documentation. Witness testimony evidence is further down the order of "strength" but there is little point in pursuing the full topic of "Evidence 104" either in the legal setting or the scientific equivalents.
It's evidence that someone claims to have experienced something, not evidence that it happened
You are still confusing "what happened" with "what evidence supports it" (And a couple more differences but let's clear up our primary misunderstanding first.)

Until we clear up this main confusion there is no point in me addressing the remainder of your comments.
You may call that circular reasoning but I call it critical thinking and rational thought, Eric Conley.
Do you really want to play the game that way?

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benthamitemetric

Senior Member
If witness testimony could be considered evidence for CD then NIST would have investigated CD. You may call that circular reasoning but I call it critical thinking and rational thought, Eric Conley.
Whether or not NIST investigates a phenomena has no inextricable logical connection to whether such phenomena occurred. That's putting far too much importance on NIST as an infallible arbiter of cosmic truth, which it is not. That said, NIST did investigate controlled demolition theories using the evidence available and, on the basis of that evidence, determined (correctly) that they were meritless.

Staff member
The topic is,

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