Goodbye, Mr Roberts

[c1ue]

Re: Goodbye, Mr Roberts

Huh? That last sentence made no sense. If floor X could hold the weight of the floors above it, then why would it collapse under less force?

Because there is a difference between a force built up over weeks (during construction) vs. an instantaneous force.

Certainly it is possible still that the lower floors could withstand this instantaneous force, but Chandler et al fail to do any type of consideration in this respect.

The WTC steel structure - whether in entirety or just the lower portion - is not an ideal substance. A clue on the propagation time can be inferred from the vibration induced by the plane impact: 0.6s to 0.7s. This vibration can be said to be the effect of a lateral force on the structure travelling up and down said structure as a wave until damped out.

Why does this matter? Because the total available load capacity is limited by the amount of steel structure reachable in this propagation time.

So even in the case where the total force from the upper floors falling is less than the force of the weight of the upper floors at rest, there are still significant qualitative differences which could still explain a structural collapse.

Chandler's argument is that at the instant of t = 0 (collapse) that the lower structure is already exerting a sufficient force capacity to support the upper structures - i.e. the load capacity is sufficient and there is no impact propagation issue.

But this is likely be wrong. Because even if the upper stories fell only 1 meter, the time to fall this distance is 0.45s (a 3 meter fall is 0.55s) [using the equation sqrt(2*distance/gravity) = t] which is likely much higher than the propagation time within the WTC structure. This means the previous resistance force will have completely dissipated by the time the upper stories actually (re) contacted the lower structure. The lower structure would thus have at least much less, possibly zero 'resistance' force.

Chandler fails to even mention this - hence his credibility is reduced.

[radon]

Re: Goodbye, Mr Roberts

Could you be more explicit in your suggestion, radon? I missed your point.

My point in that example is that both you and skyson seem to be under some mistaken impressions about force. For instance in the above example it appeared to me that both you and skyson thought that the rife and bullet ended up with the same energy because of newtons 3rd law. This is clearly not the case and it is an example of what Chandler is attempting to exploit.

When structures deform and decompose energy is transfered and this happens over time. In the, albeit distant now, past I have had some success with getting people to understand the nature of a limit and what its implications are when dealing physics by introducing Zeno's paradox. Sometimes it help people realize how important time is and why Newton's calculus is so useful.

In any case, here's one more attempt at explaining what I think is shown by Chandler's work.

Let's say that the official story is correct. In particular, the upper floors suffered critical damage from the plane impacts and subsequent fire, so started to collapse. This much even I could agree with. Whatever floor (80 or 100 or whatever) was most damaged would begin rapid failure. The floor above, already weakened itself by the rising fires, would come down and fail, and so forth, with catastrophic failure rapidly moving up from the point of initial failure, somewhere around the 80 or 100th floor, whatever it was.

So far, so good. Even I find that plausible.

Now what happens to the floors below the impact zone. So far as I understand from the official story, these stories, up until the moment of general collapse, were in pretty good shape. Some have argued that the steel in these lower floors could have been already heated to the point of significant weakening; that I strongly disagree with.

For the sake of discussion, allow me to assume for the rest of this post that the steel in the 80 or 100 floors below the impact zone was at pretty close to full strength and structural integrity, right up to the point of general collapse. If that assumption is wholly unacceptable to you, then you can skip the rest of this post ... oh well.

Ok, so what do we have at this point? We have the upper floors collapsing rapidly onto the lower floors. Now by the official story, if I understand it correctly, these falling and self-destructing upper floors essentially crushed the lower floors, top down, bang, bang, bang, one floor at a time, all the way to the ground. First the top of the building (above the impact zone) weighed too heavily on the severely damaged impact area, crushing it, and then all that stuff, including the still partially formed upper most floors and debris, came crushing down on the lower floors, top down, one floor at a time. Hopefully I am presenting the official story correctly here.

Ok let's ask what it would take to crush one of the heretofore undamaged lower floors. It would take pressing or impacting on it with more force than the normal static load of whatever was above it, right? Rather obviously, an undamaged floor N could support the full static weight of all floors N+1 up to the roof. The reason (by the official story) that floor N failed suddenly was that it rather suddenly got impacted with more than that amount of force, that is with more than the static weight of the floors above it. It got hit with the dynamic weight of those floors falling. Each floor below the original impact zone got hit with more force than the normal static load of those floors above it, right?

I claim that the following three statements are true for any (small, relative to the earth) object falling toward the earth (or other large mass):

• If the falling object is met with a force that's equal to the weight of that object, it continues to fall at constant velocity.
• If the falling object is met with a force that is greater than it's weight, it falls slower (decelerates.)
• If the falling object is met with a force that is less than it's weight, it falls faster (accelerates.)

The "small" and "large" are not essential to the mechanics involved, but are suggested by the common use of such words as "falling" and "weight". I may be bigger than the average human (most cows are ), but no one (to my face) speaks of the earth falling toward my mass .

Anyway, confirm for yourself if you will that the above three statements are true.

Chandler's observations demonstrate that the upper building was "falling faster". Upper WTC1 was accelerating downward at 6⁺ m/secē and upper WTC7 was accelerating downward at 9⁺ m/secē. Therefore, by the third statement above, upper WTC1 and WTC7 were each "met with a force ... less than it's weight."

So, for any floor X between 1 and the bottom of the impact zone (or whatever the equivalent was for WTC7?), we have that floor X was structurally sound and at roughly full strength, until suddenly, it was met with a force less than that which it had been supporting, causing it to collapse catastrophically.

Huh? That last sentence made no sense. If floor X could hold the weight of the floors above it, then why would it collapse under less force?

A) Obviously the support column can withstand a great deal of force. But nothing is moving, there is no mechanical energy being transfered. In a collapse this is not the case. The forces change dramatically over time, but your force diagram of the initial state doesn't tell you about that. Also when hard things things run into each other they experience very high accelerations for short periods of time. What happens to your floor when it experiences a couple hundred thousand times the force it was designed to support over the course of a tenth of a second? Generaly the result is catastrophic failure.

B)These are not homogeneous structures. The floors are suspended and aren't supporting anything. This is a large tube with support columns in the center. Once the support columns become misaligned, for whatever reason, they will fall all the way to the ground without encountering significant resistance. And yes, the previously suspended floors will pancake all the way down.

What I would have expected Chandler's measurements to find, if the official story was correct, is that the falling upper portion decelerated (slowed down) as it impacted the lower portion that was being crushed by reason of suddenly having more force down on it than the normal static load it bore. The falling portion would decelerate (fall slower), most likely losing all velocity before reaching the ground, leaving the remaining floors below that point still standing.

Why would anyone expect that when the entire building is experiencing a continuous acceleration of 9.8m/s. It appears to me that Chandler is both using F = d(mv)/dt without the notion of time, and misapplying it when he should be using the work energy theorem. He is also deliberately misrepresenting the very structural details that contributed to the collapse. I'll go further and say that if he is a physicist he has deliberately constructed this argument to prey on the public. I find this brand of solipsism to be distasteful.

[Ghent12]

Re: Goodbye, Mr Roberts

I claim that the following three statements are true for any (small, relative to the earth) object falling toward the earth (or other large mass):

• If the falling object is met with a force that's equal to the weight of that object, it continues to fall at constant velocity.
• If the falling object is met with a force that is greater than it's weight, it falls slower (decelerates.)
• If the falling object is met with a force that is less than it's weight, it falls faster (accelerates.)

The "small" and "large" are not essential to the mechanics involved, but are suggested by the common use of such words as "falling" and "weight". I may be bigger than the average human (most cows are ), but no one (to my face) speaks of the earth falling toward my mass .

Anyway, confirm for yourself if you will that the above three statements are true.

Chandler's observations demonstrate that the upper building was "falling faster". Upper WTC1 was accelerating downward at 6⁺ m/secē and upper WTC7 was accelerating downward at 9⁺ m/secē. Therefore, by the third statement above, upper WTC1 and WTC7 were each "met with a force ... less than it's weight."

Think of it this way: What happens at the very first instant that any part of the upper section impacts any part of the lower section? Would the upper section's velocity be instantaneously reduced to zero, since it is met with sufficient normal force to hold up the structure during normal conditions? If the velocity changes from its fall speed to zero at one exact instant, doesn't this mean "infinite or undefined" acceleration; hence "infinte or undefined" force*?

As Chandler did not go into a structural analysis of steel except to say that the force involved during collapse was much lower than the normal force applied while witholding the weight of the buiding, what would Chandler say of any structure being subjected to infinite or undefined force? It would be destroyed, of course. The questions are where and when? The answer to where is easy even for Chandler; at the point(s) where the structure is weakest, likely along welds and other connections. The answer to when is not attainable using Chandler's analysis. For that, you need to consider far more complex approaches, incuding energy balance, dynamic modulus of elasticity, and so forth.

In the larger sense, what happens after the top floor of the lower section (or the top parts of the support columns) fracture when subjected to this "infinite or undefined" force? They (and yes skyson, the bottom parts of the load-bearing structure of the upper section) fracture and fall to earth. But now the point below the fracture of the upper parts of the veriticle columns on the lower section (which is the highest load-bearing area of the remaining intact lower section) are subjected to the impact of the portion of the lower section which was recently destroyed and is now falling to earth, the lower part of the upper section that was destroyed and is now falling to earth, and the remainder of the load-bearing parts of the upper section.

In aggregate, the remaining intact portion of the lower section is subjected to even more mass falling onto it at ever-increasing speeds. Also in aggregate, over the 2.5 or so seconds that Chandler sees -6.3 m/s2 acceleration or whatever, the body has aleady fallen through dozens of stories going through a series of "infinite or undefined" instantaneous forces.

* - In reality, any "infinite or undefined" force causes physical material to move, which instantaneously lowers its force to appreciable numbers, and therefore is more a theoretical concept than a real one. If a line or wire under complete tension is subjected to any force perpendicular to it (a pinky, a bird on a taught wire, etc.), then it also undergoes "infinite" force and gives way. Hence concrete moves away from your car as you drive over it, even if on a nearly microscopic level. Think of the question regarding the impact between an unstoppable force and an immovable object, then realize that there are no immovable objects (except perhaps ideas).



Further, as you will probably point out, the velocity of the falling structure did not instanteously change to zero. It was slowed as the material it impacted reached a force that exceeded that which it could withstand. Even a very tiny change in velocity can mean an extremely large acceleration (hence force) on a very very tiny time scale. Chandler's model, again, is insufficient to account for this. But ask yourself this, what happens after this extremely large force breaks the load-bearing capacity of what it impacts? Answer: the fall continues, along with newly broken things. A timescale of 2.5 seconds (where Chandler observed lower-than-gravity acceleration) is geologic by comparison of the timescale involved in impact, hence the enormous spikes in normal force, enough to break the verticle columns at their weak points, get averaged into the gravity-accelerated falling to produce an average acceleration of less than gravity's acceleration.

[Ghent12]

Re: Goodbye, Mr Roberts

Why would anyone expect that when the entire building is experiencing a continuous acceleration of 9.8m/s. It appears to me that Chandler is both using F = d(mv)/dt without the notion of time, and misapplying it when he should be using the work energy theorem. He is also deliberately misrepresenting the very structural details that contributed to the collapse. I'll go further and say that if he is a physicist he has deliberately constructed this argument to prey on the public. I find this brand of solipsism to be distasteful.

I agree wholeheartedly. I hope that he is not teaching high school kids (or anyone) any longer.

[c1ue]

Re: Goodbye, Mr Roberts

A timescale of 2.5 seconds (where Chandler observed lower-than-gravity acceleration) is geologic by comparison of the timescale involved in impact, hence the enormous spikes in normal force enough to break the verticle columns get averaged into the gravity-accelerated falling to produce an average force of less than the normal force.

I think you meant either average velocity or average acceleration.

[Ghent12]

Re: Goodbye, Mr Roberts

I think you meant either average velocity or average acceleration.

Yes, I will correct that.

[ThePythonicCow]

Re: Goodbye, Mr Roberts

Because there is a difference between a force built up over weeks (during construction) vs. an instantaneous force.

Force is force; the question is how much. It can be a static force, due to the weight of a mass in a gravitational field, or a dynamic force, evidenced by an accelerating mass.

Certainly the force of a hammer striking something solid is greater than the force (weight) of a resting hammer. But the force of a hammer striking air is less than the force of the resting hammer, because the air does not resist. You know that from personal experience. You do not feel any noticeable resisting force on a hammer as you swing it through the air. Even the force of a large hammer striking a soft marshmallow is less than the force a resting hammer imposes on its support, for the soft marshmallow cannot resist with much force, not even enough force to support the static weight of any decent sized hammer.

If one has the opportunity to measure the acceleration of a dropped hammer onto some material, one can determine whether that material could have supported the static weight of the hammer by the amount of force with which that impacted material resists the fall of the hammer.

Certainly it is possible still that the lower floors could withstand this instantaneous force, but Chandler et al fail to do any type of consideration in this respect.

Huh? This is exactly what Chandler does measure and analyze. He determines just how much such force was applied (substantially less than the static weight, as evidenced by the continued acceleration downward) and observes that the lower floors could easily support this (even if they had no over designed capacity whatsoever), unless something destroyed them first.

Chandler's argument is that at the instant of t = 0 (collapse) that the lower structure is already exerting a sufficient force capacity to support the upper structures - i.e. the load capacity is sufficient and there is no impact propagation issue.

Well, yes, prior to collapse, the lower portion supported the upper, but after collapse initiation, it didn't. The quite constant downward acceleration of the entire upper portion, hence across some entire cross section of the building, after collapse initiation tells us that there were not sufficient local affects that some apparent downward acceleration could have been due to local impact propagation issues pushing something else up at the same time. It all came down.

Something was (rather suddenly) weakening the lower floors below their normal capacity. We (well, some of us) know that something was not the impact of the upper portion, because the upper portion was not decelerating on impact, but continuing to accelerate right through what should have been (by the official story) intact floors.

Something was causing massive, floor-wide, catastrophic, explosive collapse, rapidly working down the towers (or up WTC7). That something was not the impact of the falling upper portion, because the falling upper was not slowing on impact, it was speeding up right though what should have been the impact at 2/3's free fall (WTC1) or almost complete free fall (WTC7.)

The lower structure would thus have at least much less, possibly zero 'resistance' force.

Until something or other inflicts some serious damage on a part of the lower structure, the lower structure has a demonstrated load capacity at least equal to the weight of the building normally above it. Perhaps I missed your point, but it seems to me that you saying this capacity was zero or something close. Well, on that point I'd agree. Indeed Chandler's work tells us just that. When the upper fell into the lower, the lower resisted little, allowing the upper to continue to accelerate downward.

The question is what destroyed most or all of the load bearing capacity of the lower prior to impact.

[Slimprofits]

Re: Goodbye, Mr Roberts

Newt Gingrich at the Southern Republican Leadership Conference says they should campaign on lower interest rates as part of the platform in the fall.

How does that work?

[cjppjc]

Re: Goodbye, Mr Roberts

Newt Gingrich at the Southern Republican Leadership Conference says they should campaign on lower interest rates as part of the platform in the fall.

How does that work?

Best laugh I had all day. Thanks.

[Ghent12]

Re: Goodbye, Mr Roberts

Huh? This is exactly what Chandler does measure and analyze. He determines just how much such force was applied (substantially less than the static weight, as evidenced by the continued acceleration downward) and observes that the lower floors could easily support this (even if they had no over designed capacity whatsoever), unless something destroyed them first.

Bolded emphasis is mine.
That statement is incorrect. Chandler exactly measured the average acceleration and hence approximated the average force over a very long period of time. No analysis or attempt at analysis was made regarding the instantaneous impact between any objects within the event.

Chandler's analysis is equivelent to someone claiming to find an immortal single-cell bacteria because the population of said bacteria in their petri dish only ever increases and never decreases. Obviously since the rate of growth was positive, that must mean no deaths occured, right? Such a simplistic conclusion obviously ignores the rate of death, which, being lower than the rate of binary fission, leads to an increase in the average number of cells.

Similarly, that's like comparing world population at the year 1900 and the year 2000 and coming to the conclusion that nobody died. There were no wars, and if there were, nobody died in them. This must be true, because the average force was lower than its normal fo-- err, I mean because the average population increased.

When you ignore minutia and then claim that those minute events such as WW2, cell death, and column impact/failure, etc. must be impossible, you have done an analysis that is insufficient to come to that conclusion.

[ThePythonicCow]

Re: Goodbye, Mr Roberts

My point in that example is that both you and skyson seem to be under some mistaken impressions about force. For instance in the above example it appeared to me that both you and skyson thought that the rife and bullet ended up with the same energy because of newtons 3rd law. This is clearly not the case and it is an example of what Chandler is attempting to exploit.

You switch from force to energy in mid paragraph (and back a few words later, referencing Newton's laws), so I cannot know what you meant, nor comment coherently on your claim that we're mistaken. When a bullet leaves a gun, the gun has an equal and opposite momentum (mv: mass times velocity) to the bullet. Force is evidenced as a change in momentum over a time interval (F = d(mv)/dt = ma, for constant mass.)

A) Obviously the support column can withstand a great deal of force. But nothing is moving, there is no mechanical energy being transfered. In a collapse this is not the case. The forces change dramatically over time, but your force diagram of the initial state doesn't tell you about that. Also when hard things things run into each other they experience very high accelerations for short periods of time. What happens to your floor when it experiences a couple hundred thousand times the force it was designed to support over the course of a tenth of a second? Generally the result is catastrophic failure.

The highlighted sentence above describes exactly what Chandler's measurements demonstrate conclusively did not happen. We now know for a fact that some lower (ostensibly heretofore undamaged) floors did not experience greater (or even close to the) force (than static load) when the falling floors fell to their level, exactly because it is now an uncontested fact that the upper falling flows did not decelerate through the time period of impact and destruction of those lower floors. Rather what happened is that the falling upper floors continued to accelerate at nearly (2/3's) or all of free fall.

That you would place such a sentence in this discussion proves to me beyond any reasonable doubt that you do not understand what was the central result of Chandler's measurements.

B)These are not homogeneous structures. The floors are suspended and aren't supporting anything. This is a large tube with support columns in the center. Once the support columns become misaligned, for whatever reason, they will fall all the way to the ground without encountering significant resistance. And yes, the previously suspended floors will pancake all the way down.

You're ingenious :rolleyes:. This is yet a new collapse theory. You suggest that somehow the center support columns were dislodged and fell to the ground, relatively unimpeded, allowing the floors (no longer adequately supported) to pancake.

I will give you credit for creativity. Now can you suggest to me how any part of the core columns -below- the impact zones of WTC1 or WTC2 became dislodged (without, of course, significantly slowing the near free fall downward acceleration of what was above them)?

Why would anyone expect that when the entire building is experiencing a continuous acceleration of 9.8m/s.

Your comment is incoherent. We're all (on the surface of this planet) experiencing a gravitational force which if unopposed (free fall) is sufficient to accelerate us toward the center of the earth at 9.8 m/secē. But most of us, most of the time, are thankfully not accelerating up or down at all. We are walking, standing, sitting or laying on supports that provide an equal and opposite force.

It seems you will require a better understanding of such concepts as mass, force, energy, momentum, acceleration and gravity in order to master this material. Good luck.

It appears to me that Chandler is both using F = d(mv)/dt without the notion of time, and misapplying it when he should be using the work energy theorem. He is also deliberately misrepresenting the very structural details that contributed to the collapse. I'll go further and say that if he is a physicist he has deliberately constructed this argument to prey on the public. I find this brand of solipsism to be distasteful.

Chandler has a quite clear time scale, obtained from the sequential frames of the videos he analyzes, which have a precise and well known timing. I am rather baffled by your comment that it appears otherwise to you.

There is no reason Chandler should use an analysis of work and energy instead of his analysis of force and acceleration. Both analyses can be performed. He is not wrong in his choice of analytic methods just because you know of another.

Indeed, in this case it seems that the energy analysis is inconclusive (collapse is plausible, if I understand c1ue's work on this) but the force and acceleration analysis is conclusive -- something else mostly (in WTC1) or entirely (in WTC7) destroyed the load bearing capacity of those lower floors prior to when the falling upper floors fell to impact what remained of them.

When I have one analysis that proves a conclusive result and another analysis that is inconclusive, I find the former analysis more useful.

Finally, your conclusion that Chandler is deliberately (if he is a qualified physicist who presumably knows better) engaging in solipsism is less than persuasive, given the confusions I have noted above in your comments.

[Ghent12]

Re: Goodbye, Mr Roberts

The highlighted sentence above describes exactly what Chandler's measurements demonstrate conclusively did not happen. We now know for a fact that some lower (ostensibly heretofore undamaged) floors did not experience greater (or even close to the) force (than static load) when the falling floors fell to their level, exactly because it is now an uncontested fact that the upper falling flows did not decelerate through the time period of impact and destruction of those lower floors. Rather what happened is that the falling upper floors continued to accelerate at nearly (2/3's) or all of free fall.

That you would place such a sentence in this discussion proves to me beyond any reasonable doubt that you do not understand what was the central result of Chandler's measurements.

You must have me on your ignore list by now. C'est la vie. Chandler's measurements did not prove any such thing. They proved that the average acceleration was lower than that of gravity, and Chandler surmised that this meant that the average force was less than the normal force. If you add together a million different instances in time where the acceleration is exactly -9.81 m/s2 (freefall) with three thousand instances where the acceleration is on average +981.0 m/s2 (an extreme impact number), the average acceleration becomes roughly -6.84 m/s2. Kinda close to exactly what was observed, no?

[c1ue]

Re: Goodbye, Mr Roberts

Force is force; the question is how much. It can be a static force, due to the weight of a mass in a gravitational field, or a dynamic force, evidenced by an accelerating mass.

Force is force - and it isn't energy. Nor is it speed/velocity. Nor is it acceleration. Force is like voltage. Until you have current (time <=> distance), it is meaningless.

Certainly the force of a hammer striking something solid is greater than the force (weight) of a resting hammer. But the force of a hammer striking air is less than the force of the resting hammer, because the air does not resist. You know that from personal experience. You do not feel any noticeable resisting force on a hammer as you swing it through the air. Even the force of a large hammer striking a soft marshmallow is less than the force a resting hammer imposes on its support, for the soft marshmallow cannot resist with much force, not even enough force to support the static weight of any decent sized hammer.

I'm not sure what you're trying to say here. The force of a hammer whether being swung or purely due to gravity at rest are both values for which the force loading capacity of the marshmallow is insufficient.

Swinging a hammer at a harder object gets you some reactive force, but that is again due to a great force loading capacity.

The resistance in every single case above is a function of the force loading capacity of the object hit: a high force loading capacity means the swung hammer bounces back to some degree. A low force loading capacity means the reactive force is low and likely unnoticeable.

But the part you're missing - as is Chandler - is that if the force is sufficient to break the struck object (not pierce), how much actual energy is lost by the hammer in breaking the struck object? Piercing is a different function because a nail doesn't actually break the structure of the board, though it does deform the marshmallow.

The energy 'lost' isn't the full force loading.

Huh? This is exactly what Chandler does measure and analyze. He determines just how much such force was applied (substantially less than the static weight, as evidenced by the continued acceleration downward) and observes that the lower floors could easily support this (even if they had no over designed capacity whatsoever), unless something destroyed them first.

No he doesn't, because

1) He treats everything as if it were ideal: i.e. WTC upper and lower behave as single ideal coherent objects
2) He doesn't examine the details on how the load distribution might change with a 1/4 or 1/5 of core structure severed
3) He doesn't take into consideration the difference between static and dynamic load
4) He doesn't deal with energy - only momentum and force, both of which are only secondary effects from the primary interactions.

Well, yes, prior to collapse, the lower portion supported the upper, but after collapse initiation, it didn't. The quite constant downward acceleration of the entire upper portion, hence across some entire cross section of the building, after collapse initiation tells us that there were not sufficient local affects that some apparent downward acceleration could have been due to local impact propagation issues pushing something else up at the same time. It all came down.

Again, you are treating dynamic and static loading as identical.

They are not.

Until something or other inflicts some serious damage on a part of the lower structure, the lower structure has a demonstrated load capacity at least equal to the weight of the building normally above it.

A massive weight striking a dynamic blow to the lower structure could easily have inflicted major damage.

As I noted in the previous post - the impact of the 767 caused a tremor in the entire structure of 0.6s to 0.7s. This tremor can be considered a function of the impact as a wave travelling up and down the entire structure multiple times. How many? I have no clue but it is likely at least 4 or 5 trips.

If so, this means a propagation velocity of over 0.1s, or more importantly if an instantaneous blow is struck, only 1/5th of the structure would 'see' the impact.

This is but one example of how large scale, high energy environments like the WTC towers differ from billiard balls.

Chandler et al fail to address this. They assume everything is ideal - an assumption which is fine in a normal architectural sense, but is not in a dynamic environment.

[radon]

Re: Goodbye, Mr Roberts

You switch from force to energy in mid paragraph (and back a few words later, referencing Newton's laws), so I cannot know what you meant, nor comment coherently on your claim that we're mistaken. When a bullet leaves a gun, the gun has an equal and opposite momentum (mv: mass times velocity) to the bullet. Force is evidenced as a change in momentum over a time interval (F = d(mv)/dt = ma, for constant mass.)

I don't see how what I said was ambiguous. I also don't see how you would find me mentioning the work-energy theorem and force in the same sentence confusing. I did want to show that following his line of reasoning is deceptive and will lead to and incorrect conclusion, and that was the reason I chose it as an example.

The highlighted sentence above describes exactly what Chandler's measurements demonstrate conclusively did not happen. We now know for a fact that some lower (ostensibly heretofore undamaged) floors did not experience greater (or even close to the) force (than static load) when the falling floors fell to their level, exactly because it is now an uncontested fact that the upper falling flows did not decelerate through the time period of impact and destruction of those lower floors. Rather what happened is that the falling upper floors continued to accelerate at nearly (2/3's) or all of free fall.

That you would place such a sentence in this discussion proves to me beyond any reasonable doubt that you do not understand what was the central result of Chandler's measurements.

Chandlers measurements show the floors accelerate at some rate less than 9.8m/ss. This is exactly what is expected. Furthermore things coming to a sudden stop undergo a great deal of acceleration, and the resulting amount of force can cause the materials involved to decompose. Collisions are not perfectly elastic. There is no conspiracy required.

You're ingenious :rolleyes:. This is yet a new collapse theory. You suggest that somehow the center support columns were dislodged and fell to the ground, relatively unimpeded, allowing the floors (no longer adequately supported) to pancake.

I will give you credit for creativity. Now can you suggest to me how any part of the core columns -below- the impact zones of WTC1 or WTC2 became dislodged (without, of course, significantly slowing the near free fall downward acceleration of what was above them)?

I consider falling beams misaligned. If they were properly supported they would not be falling right? Anyway how is this a new theory, and where did I imply that they became dislodge below the impact zone? Those columns are heavy and built to carry the load of the structure. They will fall right through the lightly built floors below them with little resistance. As far as a few hundred tons of falling steel is concerned the interior is mostly space.

Your comment is incoherent. We're all (on the surface of this planet) experiencing a gravitational force which if unopposed (free fall) is sufficient to accelerate us toward the center of the earth at 9.8 m/secē. But most of us, most of the time, are thankfully not accelerating up or down at all. We are walking, standing, sitting or laying on supports that provide an equal and opposite force.

It seems you will require a better understanding of such concepts as mass, force, energy, momentum, acceleration and gravity in order to master this material. Good luck.

And we all skate around on frictionless surfaces too. Forces are static and well behaved. Collisions are perfectly elastic and materials are immutable. I like to make things up too but the real world isn't like that. What happens when a few thousand tones of your closest friends needs to stop in a few centimeters. What kind of opposing force would you need for that? What sort of buildings outside of bomb shelters are designed to supply it?

Chandler has a quite clear time scale, obtained from the sequential frames of the videos he analyzes, which have a precise and well known timing. I am rather baffled by your comment that it appears otherwise to you.

There is no reason Chandler should use an analysis of work and energy instead of his analysis of force and acceleration. Both analyses can be performed. He is not wrong in his choice of analytic methods just because you know of another.

Indeed, in this case it seems that the energy analysis is inconclusive (collapse is plausible, if I understand c1ue's work on this) but the force and acceleration analysis is conclusive -- something else mostly (in WTC1) or entirely (in WTC7) destroyed the load bearing capacity of those lower floors prior to when the falling upper floors fell to impact what remained of them.

When I have one analysis that proves a conclusive result and another analysis that is inconclusive, I find the former analysis more useful.

Finally, your conclusion that Chandler is deliberately (if he is a qualified physicist who presumably knows better) engaging in solipsism is less than persuasive, given the confusions I have noted above in your comments.

This has nothing to do with energy based analysis. I like Hamiltonian mechanics as well as the next person, but my example has nothing to do with it. I used work energy it to illustrate that his argument using only static force is misleading.

Also, my complaint, assuming he knows better, is that his is deliberately preying on people with an unsophisticated physics background using an argument that everyone can understand but is incorrect. This kind of poppycock Chandler foists on people is tempting and people want to believe it, but it has no basis in reality.

In any case now that everyone is talking in circles and there is no budging I think this thread has run its course for me at least. I'm not indefatigable like the others.

[ThePythonicCow]

Re: Goodbye, Mr Roberts

Thank you for responding, radon.

For the record, I found your latest reply mostly just introduced more confused or incorrect statements, without really addressing any of the previous points I raised.

Since you state you've about run out of energy for this, I will not spent time that would likely be wasted, responding in detail.

If there is anyone left reading this thread who found something radon said interesting, and if they would like my reaction, please post such a request. I'll be quite surprised to see such, but if I do, the odds are good I will make the effort to respond.

===

This thread has been an interesting study in the capacity of the human mind to deceive itself.

I began my efforts to discuss the events of 9/11 on iTulip thinking it was a keystone event; that a correct understanding of what happened that day shed a whole new light on our government and institutions; that a correct understanding of the deeply fraudulent nature of our government and major institutions was essential to a proper understanding of our economic circumstances and futures; that we needed to know what was wrong in order to know both how to survive and how to improve things.

I joined iTulip a year and a half ago after leaving my previous "home on the web", Freerepublic.com (a right wing political site), because it was not open to (heck, it was downright hostile to) the truth about 9/11. iTulip has (reluctantly, but still) allowed this discussion (that it's on Rant & Rave is fine by me) for which I am grateful.

Now I find myself darker, more cynical, more discouraged than I have been since sometime 40 or 50 years ago in late adolescence. The deceit is not just in our institutions. It is deeply embedded in the minds of many if not most of even our smartest, best informed people. The situation is more dire than I realized.

Perhaps this shows the essential reason that those far wiser than I have been encouraging us to think and work locally for now. Find some small garden of life that is still reasonably healthy and focus ones energies there. If one looks over the parapet to see what's happening in the larger world, as I've done the last two years, the risk is that one will be destroyed by the horror one sees, that one will have one's life sucked out. But in times of great change and tension, if one does not look about at the larger situation, one risks being swept aside by a tsunami one could have avoided, had one but noticed the signs of its arrival sooner.

What we've seen here on this thread is an example of the success of modern propaganda methods. Evil has run amok in human civilization in so many ways and on such a vast scale that I've lost track.

I had hoped to shine a small light of truth for others, and instead the darkness envelopes me like a fog in the night.

9/11 was the watershed event of our times. Score: humans 0, sociopaths 1.