Goodbye, Mr Roberts

[ThePythonicCow]

Re: Goodbye, Mr Roberts

The answer to the bold portion, once again, is dynamic loading.

Wrong. If you had the same physics professor as c1ue, then perhaps the two of you should consider initiating a class action lawsuit against him for malpractice .

I've already explained it multiple times above. Chandler explains it clearly in his papers and videos. I hold virtually no hope that I can get you to understand, but foolish cow that I am, I will try one more time.

Let me perform two experiments with your bowling ball. Perhaps using that familiar object will help.

Imagine the following two experiments.

1. In the first experiment I lay flat on my back on the floor and you drop a bowling ball on my chest from a height of 25 feet. The bowling ball is light enough and my chest strong enough that I would have been able to support the static weight of the ball on my chest without injury. Let's say it's a 20 pound ball. My rib cage and bones are strong; I can support that easily enough.
   
   Now let it drop.
   
   Hmm ... guess we'd better perform this first experiment second, 'cause I just got killed when that falling bowling ball crushed my chest -- oops :eek:
   
   Anyhow (perhaps as part of the autopsy) let's calculate what happened.
   
   Presume two more things: that the floor I was laying on is a massive immobile steel reinforced concrete structure, and that my chest slowed down that falling ball as "gently" as possible with my still having a chance to survive, say over a depth of 0.5 feet.
   
   Then by my calculations, the ball hits my chest moving at a velocity of V = √(2 * 32 * 25) = 40 ft/sec. The basic formula I used (solved for V) was Vē = 2*A*S, where V is Velocity, A is acceleration (Gravity of 32 ft/secē in this case) and S is distance (the 25 feet)
   
   While the falling ball is decelerating from 40 ft/sec to 0 ft/sec through the 0.5 feet of my chest, it is exerting a force of its weight, plus whatever force is needed to decelerate it (what you termed dynamic loading, I presume) from 40 ft/sec to 0 ft/sec in that 0.5 foot. That deceleration is found using the same equation as above, this time solved for acceleration (deceleration, actually) X = Vē/ (2 * S), where X is the deceleration, V the velocity (-40 ft/sec) and S the distance (0.5 ft). This yields X = -40ē / (2 * 0.5) = -1600 ft/secē This -1600 deceleration is 50 times Gravity, so that deceleration is imposing a force on my chest of 50 times the gravitational force that the ball would impose if it motionless in 1 Gravity field. This computes to 50 * 20 lb = 1000 lb. Adding these two forces (deceleration and Gravity) together, we get a force of 1000 + 20 = 1020 lb on my chest.
   
   I'm crushed.
   :eek::eek:
2. In the second experiment (done first for the reason noted above) I am first strapped, laying on my back, to a platform firmly attached to a fancy elevator contraption that can move my prone body up or down in whatever rapid, precisely controlled, motions one desires.
   
   Now let's program the elevator contraption to accelerate me sharply downward as the falling bowling ball hits my chest. We program this motion to accelerate me downward at the rate necessary to reduce the impact force of that falling ball sufficiently that, while it continues to accelerate (faster, faster, ...) downward, it is now only accelerating downward at just under 2/3's Gravity (about -20 ft/secē) rather than at freefall (-32 ft/secē) Gravity (ignoring air friction.)
   
   Let's further suppose that we built this fancy elevator contraption over the granite bedrock beneath Manhattan and that the elevator will stop instantly (in less than 1 mm distance say) if it is ever driven down all the way to the bedrock. We've got a Wiley Coyote scene here, with me hurtling to my certain death, a 20 lb anvil (or ball, as the case be) on my chest, to the canyon floor.
   
   I won't bother to presume some distance for the depth of the hole (say it's a few hundred feet) nor to then calculate the forces, times, velocities or accelerations. The results are quite clear and I'm sure we will all agree on them. It did not matter after all which experiment I did first; they're both quite lethal.
   
   Faster, faster, faster, down I go, with the weight pressing quite gently on my chest (pushing on it with a force less than 1/3 it's static weight of 20 lb), until I hit bedrock with a resounding SPLAT! (and the ball then pulverizes any remaining sinew of my chest.)
   :eek::eek:

By now you're probably thinking what the heck; the cow has dug himself quite a hole here and buried his argument a few hundred feet below ground level in downtown Manhattan. His fanciful elevator contraption (in the second experiment) is surely crushed to a billowing cloud of fine dust.

Whether his argument was crushed or went SPLAT, what did it matter? Either way, there's one less contentious cow to content with .

===

Well, sorry to disappoint you, but today is not your lucky day.

Look back up at that second experiment and notice where I emphasized "pressing quite gently". There was a period of time in the second experiment during which the bowling ball was pressing on my chest, though doing so with quite a bit LESS force than a similar ball would press when nothing was moving. My chest was not being injured during that period of time. It was feeling LESS TOTAL pressure than it would have felt if I were just resting a static bowling ball on my unmoving chest.

The fancy elevator contraption was thrusting me downward, increasingly fast, out of harm's way.

If we could measure the exact position (hence velocity and acceleration) of the ball as a function of time during that period of time, we would see that the ball was still accelerating downward, just at 2/3's Gravity instead of 1 full Gravity. From exactly such measurements we could know that for that period of time, whatever was below that bowling ball was pressing up at the ball with a force substantially LESS than a table or floor normally presses up on the bowl when it is at rest, a TOTAL force substantially LESS than the static weight of the ball. The TOTAL force from below was substantially LESS than Gravity, for it could not stop the downward acceleration, only reduce it by 1/3.

My chest received no damage during the period of time that the bowling ball was touching it, but still accelerating downward at 2/3 Gravity. The pressure on my chest was quite a bit less (just 1/3) of the pressure of a static ball.

Well, such exact measurements were taken in the WTC1 and WTC7 cases, and such results found. There was a period of time during which, for each building, many floors were being crushed into fine rapidly ejecting dust even as the falling upper portion was still accelerating downward at 2/3 (WTC1) or 1 (WTC7) Gravity.

Whatever was crushing floors during that time period (and the overwhelming and incontrovertible and uncontested evidence is that something was crushing floors during that period) was not the dynamic loading or impact forces between the upper (falling) and lower (still standing) portions of those buildings.

I'm rather sure as well that whatever it was that was "getting the lower floors out of the way" was not a fancy elevator contraption thrusting the lower towers down into a deep hole down to bedrock.

[ThePythonicCow]

Re: Goodbye, Mr Roberts

Whatever was crushing floors during that time period (and the overwhelming and incontrovertible and uncontested evidence is that something was crushing floors during that period) was not the dynamic loading or impact forces between the upper (falling) and lower (still standing) portions of those buildings.

I'm rather sure as well that whatever it was that was "getting the lower floors out of the way" was not a fancy elevator contraption thrusting the lower towers down into a deep hole down to bedrock.

I wonder what it could have been removing those pesky floors so quickly ...

[skyson]

Re: Goodbye, Mr Roberts

Wrong. If you had the same physics professor as c1ue, then perhaps the two of you should consider initiating a class action lawsuit against him for malpractice .

I've already explained it multiple times above. Chandler explains it clearly in his papers and videos. I hold virtually no hope that I can get you to understand, but foolish cow that I am, I will try one more time.

Let me perform two experiments with your bowling ball. Perhaps using that familiar object will help.
........

What else do you do in your life, COW, other than pursuing the truth?

Thanks for the elaborate experiments.

But I am lazy, so understandably, prefer simpler solutions - I don't have to prove anything, just need to disprove one thing...;)

The answer to the bold portion, once again, is dynamic loading. It's not just a computer engineering term.

q: Why can your chest withstand a ten-pound bowling ball to a safety factor of at least four (meaning it could withstand a forty-pound weight, if uncomfortably), but not withstand that bowling ball dropped from 12 feet?
a: Dynamic loading.

q: Why can a given table withstand your weight and then some, but breaks when you jump up and down on it?
a: Dynamic loading, plus cycling if applicable.

Chandler claims that the lower section was only subjected to 36% of the normal force. Perhaps that is the correct figure, perhaps not. Either way, what his simplistic, high-school level view is unable to comprehend, is the time integral involved.
q: Can the lower section withstand 36% of the previous static load if applied over the span of 10 seconds?
q: Can the lower section withstand 36% of the previous static load if applied over the span of 1 second?
q: Can the lower section withstand 36% of the previous static load if applied over the span of 10 milliseconds?
q: Can the lower section withstand 36% of the previous static load if applied over the span of 10 microseconds?
a: In reality, it is likely that the structure received close to 100% of the static load within a few milliseconds, and the normal force plus the restitution impulse were applied far too quickly in far too large a quantity for the load-bearing structure to withstand. This is dynamic loading.

What do you mean by a few milliseconds? Like 3? Where you get that number from?

You have to clarify how far the upper structure travels in that period of time. Remember, we are not talking about a missile penetrating a tank armor.

As COW mentioned in other posts, in US, high rise building common has safety factor of 3-6, meaning support structure damaged up to 67% o 83% would not result in the collapse of structure.

In the case of WTC1, I generously assume the entire 95th floor support structure was destroyed (in fact, it was about 50%-60% from what I read before, but I could not find the literature now), so the whole 16 upper floor fell onto 94th floor at free fall, and the floor height for WTC1 is 3.8 meter:

T(95) = square root(2xdistance/g) = 0.88 seconds.

Free fall time through 94th floor:

T(94) = T(95 + 94) - T(95)= 1.245 second - 0.88 second = 0.365 second.

Now I have not considered how much the resistance of the intact 94th floor would slow down the falling upper section, but this number alone is almost 120 times longer than your "few milliseconds".

Remember that when the upper floor crushing the 94th floor, it is a linear continuous collision, therefore the impact time is much much longer than your "out of no where" few milliseconds.

You scold at Chandler's "high school level review", but I beg to differ. I truly believe anyone with high school physics knowledge would be able to solve the WTC collapse mysteries. It is about basic physics and common sense. It is how the nature works. You don't need to be a cabinet minister to see the emperor has no clothes.;)

By the way, you have not answer my "high school level" challange. Please do. I am eagerly awaiting your reply.

[Ghent12]

Re: Goodbye, Mr Roberts

Wrong. If you had the same physics professor as c1ue, then perhaps the two of you should consider initiating a class action lawsuit against him for malpractice .

I've already explained it multiple times above. Chandler explains it clearly in his papers and videos. I hold virtually no hope that I can get you to understand, but foolish cow that I am, I will try one more time.

Let me perform two experiments with your bowling ball. Perhaps using that familiar object will help.

Imagine the following two experiments.

1. In the first experiment I lay flat on my back on the floor and you drop a bowling ball on my chest from a height of 25 feet. The bowling ball is light enough and my chest strong enough that I would have been able to support the static weight of the ball on my chest without injury. Let's say it's a 20 pound ball. My rib cage and bones are strong; I can support that easily enough.
   
   Now let it drop.
   
   Hmm ... guess we'd better perform this first experiment second, 'cause I just got killed when that falling bowling ball crushed my chest -- oops :eek:
   
   Anyhow (perhaps as part of the autopsy) let's calculate what happened.
   
   Presume two more things: that the floor I was laying on is a massive immobile steel reinforced concrete structure, and that my chest slowed down that falling ball as "gently" as possible with my still having a chance to survive, say over a depth of 0.5 feet.
   
   Then by my calculations, the ball hits my chest moving at a velocity of V = √(2 * 32 * 25) = 40 ft/sec. The basic formula I used (solved for V) was Vē = 2*A*S, where V is Velocity, A is acceleration (Gravity of 32 ft/secē in this case) and S is distance (the 25 feet)
   
   While the falling ball is decelerating from 40 ft/sec to 0 ft/sec through the 0.5 feet of my chest, it is exerting a force of its weight, plus whatever force is needed to decelerate it (what you termed dynamic loading, I presume) from 40 ft/sec to 0 ft/sec in that 0.5 foot. That deceleration is found using the same equation as above, this time solved for acceleration (deceleration, actually) X = Vē/ (2 * S), where X is the deceleration, V the velocity (-40 ft/sec) and S the distance (0.5 ft). This yields X = -40ē / (2 * 0.5) = -1600 ft/secē This -1600 deceleration is 50 times Gravity, so that deceleration is imposing a force on my chest of 50 times the gravitational force that the ball would impose if it motionless in 1 Gravity field. This computes to 50 * 20 lb = 1000 lb. Adding these two forces (deceleration and Gravity) together, we get a force of 1000 + 20 = 1020 lb on my chest.
   
   I'm crushed.

You claim that I don't understand physics, yet you don't seem to differentiate between rigid-body mechanics and reality. Obviously, the WTC can not be considered a complete, rigid-body for analysis as all aspects point to different parts of it moving in different ways with a large bulk amalgamating more or less in the center as it gets compacted together. Further, you still fail to understand dynamic load and other pertinent aspects. Look up the term 'modulus of elasticity' and do your homework.

Let me try to understand your claim:
The 'nano-thermite very high very quiet explosives' were timed in such a way as to allow the residual structure of the successively-demolished building to apply a normal force of 36% of the ordinary static force over a period of 2.5 seconds or so?
The -6.31 m/s2 acceleration, slower than gravity, now means that the building was now moved out of the way by explosives? I thought your earlier claims were that the building moved at near-free-fall speeds, which could only be explained by explosives as there was nothing to slow down the fall of the upper section? Now it's the other way around...
If the building collapsed at an acceleration of -3.2 m/s2, would that be even stronger proof of explosives?

Up is down to you...

Oh, and the point of quoting just your first experiment would be to say that it is substantially unlikely that your entire chest would be enough to stop the ball. There would only be two points of major resistance, so the ball would stop more or less at one of three locations; above your sternum, above your spine, or all the way through into the ground or whatever you were resting on. Then again, details only seem to matter to you when you subvert them, like raging/small fires and so forth...

[skyson]

Re: Goodbye, Mr Roberts

You claim that I don't understand physics, yet you don't seem to differentiate between rigid-body mechanics and reality. Obviously, the WTC can not be considered a complete, rigid-body for analysis as all aspects point to different parts of it moving in different ways with a large bulk amalgamating more or less in the center as it gets compacted together. Further, you still fail to understand dynamic load and other pertinent aspects. Look up the term 'modulus of elasticity' and do your homework.

Let me try to understand your claim:
The 'nano-thermite very high very quiet explosives' were timed in such a way as to allow the residual structure of the successively-demolished building to apply a normal force of 36% of the ordinary static force over a period of 2.5 seconds or so?
The -6.31 m/s2 acceleration, slower than gravity, now means that the building was now moved out of the way by explosives? I thought your earlier claims were that the building moved at near-free-fall speeds, which could only be explained by explosives as there was nothing to slow down the fall of the upper section? Now it's the other way around...
If the building collapsed at an acceleration of -3.2 m/s2, would that be even stronger proof of explosives?

Up is down to you...

Oh, and the point of quoting just your first experiment would be to say that it is substantially unlikely that your entire chest would be enough to stop the ball. There would only be two points of major resistance, so the ball would stop more or less at one of three locations; above your sternum, above your spine, or all the way through into the ground or whatever you were resting on. Then again, details only seem to matter to you when you subvert them, like raging/small fires and so forth...

No, you have not considered the safety factors of 3-5.

Notice the 36% is the weight of one safety factor.

So if redo the calculation with safety factor of 3:

36% / 3 = 12%, now meaning the 88% of strength of lower section has been eliminated.

If redo the calculation with safety factor of 5:

36% / 5 = 7.2%, meaning 92.8% of strength has been eliminated.

Since WTC was a well built structure, I would speculate the safety factor of 5.

In addition, Chandler's analysis focuses at the movement of the first 4 seconds. The NIST report puts the total collapse time as 9 seconds, that is free fall speed. "Almost free fall speed" could be 10-11 seconds. This point alone does not disprove either COW or Chandler's analysis.

P.S. please see my post #183 and #170.

[ThePythonicCow]

Re: Goodbye, Mr Roberts

But I am lazy, so understandably, prefer simpler solutions...;)

I've been doing a terrible job of explaining. Mine is incredibly simple and clearly grounded in classical Newtonian mechanics, but I cannot get c1ue or Ghent12 to break out of their intuitive model and correctly understand what I'm saying.

I'm saying thus:

The total force which a given disconnected body exerts on its surrounds is equal to and opposite of the force its surrounds exert on that given body.

The total force which a disconnected body's surrounds exert on a given body is directly proportional (F = ma) to the acceleration of that given body.

One can exactly determine the total force being exerted on a disconnected body by observing the body's acceleration. If it is accelerating in some direction, it's receiving a net force in that direction of magnitude proportionate to rate of acceleration, and it is exerting an equal and opposite force in return.

Chandler gets some clear and indisputable (even NIST final report agreed, though of course didn't draw the obvious conclusions) measurements of the downward acceleration of the falling building tops of WTC1 and WTC7.

The tops were accelerating downward at 2/3's (WTC1) or full (WTC7) Gravity.

Therefore the tops were imposing, and being imposed on by, a smaller magnitude vertical force than they normally saw at rest.

Therefore the bottoms were imposing, and being imposed on by, less vertical force from those dropping tops than when normally at rest.

Therefore any explanation of the cause of undisputed widely evidenced massive floor by floor destruction during that same time period which depends on more, not less, than static load forces between upper and lower, does not apply during this period.

This is, to be specific, the period of early general collapse when floors are failing massively and the tops are falling at increasing velocity.

The counter-intuitive aspect seems to be that a falling object might exert less, not more, vertical force than when at rest. One need only measure the vertical acceleration of a falling object to detect when this is occurring:

• Accelerating downward == less than resting force.
• Decelerating downward == more than resting force.

Mind you I'm speaking of acceleration, not velocity. The classic law is F = ma, not F = mv.

It's not the fall that hurts; it's the sudden stop ;)

I am presenting (quite poorly) straightforward observation and measurement and classical Newtonian mechanics. Chandlers measurements are easily obtained from the videos, without any second guessing of what some blurry spot means in one frame. The NIST final report was compelled to get entirely collaborating measurements, though they then had to obfuscate the implications, for the proper implications would otherwise have dis-proven NIST's analysis.

His calculations on that data are direct and clear. His conclusion is utterly inescapable.

The resulting opposing forces during these measured periods were substantially less than at rest, because the falling upper bodies were accelerating not decelerating downward.

It was not that the falling tops were pushing the lower floors aside, but rather that something else was first destroying the structure bearing capacity of the lower floors, allowing the upper portion to accelerate downward into a space that was no longer bearing much (WTC1) if any (WTC7) load.

===

I keep getting bogged down in efforts to connect with the flawed intuitive models of c1ue and Ghent12, hoping to get their attention with something that seems right in their flawed view, but then surprises them, startling them into a reconsideration. Perhaps they are like many people who are intelligent but not sufficiently trained in classical mechanics; it is common for one's intuitions to muddle the concepts of velocity and acceleration in ways that elude one's conscious analysis.

I don't know with certainty what the impediment to communication is, so probably should not have engaged in speculation on that matter. Whatever the case, I am failing miserably as a teacher and expositor.

===

Now I will confess to something a little embarrassing here, skyson. I have not figured out what you're saying here.

Could you try presenting your model from the top, as you might present it to a more sympathetic listener?

Is your model presented in terms you like by others or dependent on specific observations or measurements by others which might have gone unnoticed to me? If that is the case, kindly repeat or refer back to the relevant references. If that is not the case, that's fine too.

[ThePythonicCow]

Re: Goodbye, Mr Roberts

Oh, and the point of quoting just your first experiment would be to say that it is substantially unlikely that your entire chest would be enough to stop the ball. There would only be two points of major resistance, so the ball would stop more or less at one of three locations; above your sternum, above your spine, or all the way through into the ground or whatever you were resting on. Then again, details only seem to matter to you when you subvert them, like raging/small fires and so forth...

You quote my first experiment so that you can point out that I left out details of the structure of my chest, such as the fact that I have a sternum and spine.

Yes, I did indeed leave those details out. Yes, I do indeed have a sternum and a spine.

I also didn't count for you how many hairs are on my chest nor provide you with even the slightest description of my skin color (*).

So what?

Having observed that I have a sternum and a spine, but that I failed to state these facts, then it seems that the only use you make of your point is to criticize me for leaving out those details.

Is that the game you are playing? If you can find some detail that the other party did not mention, never mind whether it is important to the presentation, then it's gotcha time?

I pray you have not sunk to such rhetorical depths.

I pray that you had some thought in your mind as to why those particular details of my biological structure were important to this discussion and that you just forgot to mention the thought in your post.

So far as I can tell, my first experiment which you quoted would have been exactly as relevant if I were the only sentient bovine tube sausage in the universe.

(*) Oops - not true - I've made clear my skin color all along - black and white blotches ;).

P.S. -- Perhaps you phrase "it is substantially unlikely that your entire chest would be enough to stop the ball" hints at your motivation for making this point. Yeah, sure, I'll agree that I'd expect the ball to crush most of the tissues it impacts, going just under the one foot total distance rather than the 0.5 feet distance I used for the purposes of a convenient example. So what? My examples were to describe some physics, not to train coroners to correctly analyze deaths by falling bowling balls.

[ThePythonicCow]

Re: Goodbye, Mr Roberts

You claim that I don't understand physics, yet you don't seem to differentiate between rigid-body mechanics and reality. Obviously, the WTC can not be considered a complete, rigid-body for analysis as all aspects point to different parts of it moving in different ways with a large bulk amalgamating more or less in the center as it gets compacted together. Further, you still fail to understand dynamic load and other pertinent aspects. Look up the term 'modulus of elasticity' and do your homework.

It is my understanding that classical Newtonian mechanics applies to squishy bodies as well as rigid bodies.

One can introduce additional terms and concepts to such a discussion by way of explaining things better, doing ones best to explain things and provide useful references, or one can toss out fine sounding terms on the general topic with dismissive arrogance.

I will confess that your response which I just quoted above sounded to me like the latter.

What pray tell is dynamic load, other than just another phrase for a portion of the forces involved?

As best as I can understand the technical content of your reply, you're saying I'm not accounting for all the forces. I am certain you're wrong, if that's your point. You'll have to explain, not just toss words about dismissively, if you wish to communicate your insight successfully.

Yes, I find it quite frustrating trying to discuss this with you. I have no confidence that you have really read and understood my posts and the research of others that I have presented. Rather it seems you glance over them enough to find something to criticize, perhaps something that is missing that would be relevant for some analysis sometime or perhaps some technical term not present that your view finds relevant, and then dismiss the rest of what I present as unworthy. That does not make for fruitful discussions.

Before reading your replies I have a clear understanding which I have taken considerable effort to present in a variety of ways, hoping that one of my presentations would be informative. After reading your replies, I'm generally irritated and no more well informed.

[ThePythonicCow]

Re: Goodbye, Mr Roberts

The 'nano-thermite very high very quiet (A) explosives' were timed in such a way as to allow the residual structure of the successively-demolished building to apply a normal force of 36% of the ordinary static force over a period of 2.5 seconds or so? (B)

The -6.31 m/s2 acceleration, slower than gravity (C), now means that the building was now moved out of the way by explosives (D)?

I thought your earlier claims were that the building moved at near-free-fall speeds, which could only be explained by explosives as there was nothing to slow down the fall of the upper section? Now it's the other way around... (E)

If the building collapsed at an acceleration of -3.2 m/s2, would that be even stronger proof of explosives? (F)

Thanks for making some effort to understand.

Comments:
(A) no - not "very quiet" (though that is not relevant to particular analysis.)
(B) yes - something (I speculate explosives, for reasons of other evidence, not vital to the present analysis) must have moved the lower building out of the way fast enough to allow it to accelerate downward against only modest impediment.
(C) Aha - while true (slower than gravity) this exposes where you and I failed to communicate. The greater the downward acceleration of the upper portion, the more compelling the case that any potential impeding resistance of the lower layer was removed before it could resist. So long as the motion accelerates downward, then the impeding impact forces are less than the usual forces of static loading due to gravity. The greater (and close to one Gravity) the downward acceleration, the less the impeding forces of impact.
(D) Nothing in this particular analysis, as taken from Chandler, demonstrates that it was explosives in particular. This particular analysis demonstrates that it was not the "Falling Anvil" of the upper portion that caused the destruction of floors by force of impact. This present analysis leaves it to other efforts to discern the origins of the destructive forces.
(E) No - not the other way around, see (C) and (F).
(F) No - smaller downward accelerations indicate greater resisting force remains from the lower portion. If this is a explosive assisted demolition, smaller downward accelerations would indicate less complete removal of lower material prior to the falling upper material impacting with it.

Once you get the physics clear in your mind, (C) and (F) are rather obvious.

[ThePythonicCow]

Re: Goodbye, Mr Roberts

Chandler claims that the lower section was only subjected to 36% of the normal force. Perhaps that is the correct figure, perhaps not. Either way, what his simplistic, high-school level view is unable to comprehend, is the time integral involved.

Your insulting "simplistic, high school level" attribution is incorrect and insulting. Chandler understands his physics quite well, at a substantially level than high school. It's crap like this attribution which led me to not even attempt a reply to this portion of your post when you first made it.

But since skyson honored this comment with a reply, I will attempt one as well.

Chandler plots a serious of points (one every several video frames) over a several second time interval during the early part of the general collapse, when specific points on the substantially intact upper portion are still visible.

Using available PC software applications, he takes the first derivative (velocity) of those plotted position points. He fits a straight line to the velocity plot; it is an excellent fit. The slope of this straight line is an accurate estimate of the acceleration during that time interval. The acceleration is constant and downward at (I forget exactly, but more or less) 64% the acceleration of Gravity (Gravity being 9.8 m/secē on earth at sea level.) Since force is directly proportional to acceleration for a given mass, this tells us that the upward force applied by the stationary lower portion to the falling upper portion, averaged (by that straight line fitting mentioned above) over that time interval is 36% (100 - 64 ==> 36) of the force which the lower portion normally had to present to the upper portion, to hold it's static weight.

The time interval over which he obtained these measurements and the methods and tools of his analysis are clearly presented in his work.

I take it from your criticism that he neglected to consider a time interval that you had not yet understood Chandler's analysis when you made this post.

[skyson]

Re: Goodbye, Mr Roberts

I've been doing a terrible job of explaining. Mine is incredibly simple and clearly grounded in classical Newtonian mechanics, but I cannot get c1ue or Ghent12 to break out of their intuitive model and correctly understand what I'm saying.

.........

I don't know with certainty what the impediment to communication is, so probably should not have engaged in speculation on that matter. Whatever the case, I am failing miserably as a teacher and expositor.

Understand your frustration. Been there, done that.

I completely understand your line of thinking, errr...surprise, surprise, because I am a "truther"!

I was amazed to the fact that why the non-truthers just could not understand something so obvious to the truthers?

Until I slowly discovered that many people's mind is trapped in the a virtual cave, unable to escape:

Socrates begins by describing a scenario in which what people take to be real would in fact be an illusion. He asks Glaucon to imagine a cave inhabited by prisoners who have been chained and held immobile since childhood

.......

Suppose that a prisoner is freed and permitted to stand up. If someone were to show him the things that had cast the shadows, he would not recognize them for what they were and could not name them; he would believe the shadows on the wall to be more real than what he sees. "Suppose further," Socrates says, "that the man was compelled to look at the fire: wouldn't he be struck blind and try to turn his gaze back toward the shadows, as toward what he can see clearly and hold to be real? What if someone forcibly dragged such a man upward, out of the cave: wouldn't the man be angry at the one doing this to him? And if dragged all the way out into the sunlight, wouldn't he be distressed and unable to see "even one of the things now said to be true," viz. the shadows on the wall?

I believe the non-truthers are held prisoner within the confine of these virtual walls:
1. questioning the official theory is unpatriotic.
2. "you are with us, or with the terrorist" -- if one chooses to stand by the US government, then he simply cannot challenge the government.
3. challenge the office theory will hurt the feeling of victim families.
4. a democratic government(US) will not do evil things.
...............

We, humans, are born to be deceived. No matter how rational and logical we are, our thinking will ultimately be affected by our belief system and emotion. We are all trapped in our little caves. Some of us are more easily led out of the cave and venture into the real world, some are less willing.

Unless someone is willing to leave their familiar world - the cave, there is no good for you to tell them the beauty of the outside world. For them, the shadow under the candle has more truth than the real things under the sun.

Here are two fascinating articles:
Faulty Towers of Belief: Part I. Demolishing the Iconic Psychological Barriers to 9/11 Truth
Faulty Towers of Belief: Part II. Rebuilding the Road to Freedom of Reason

Now I will confess to something a little embarrassing here, skyson. I have not figured out what you're saying here.

Could you try presenting your model from the top, as you might present it to a more sympathetic listener?

Is your model presented in terms you like by others or dependent on specific observations or measurements by others which might have gone unnoticed to me? If that is the case, kindly repeat or refer back to the relevant references. If that is not the case, that's fine too.

No, I have a simple mind. So, please don't over guessing my words.

I was simply saying that my approach is "not to prove anything, but disprove only one thing - that the total collapse of WTCs by pure gravity is impossible", and I focus on the case of WTC1. The reason being that after studying the works of Gordon Ross, Dr. Greening, Dr. Bazant, and NIST Report, I found this approach is simple to understand, easy to prove, and the conclusion is inescapable. It only involves basic physics, common sense, and readily available documentation.

I lay out my basic points at post #170 again. So far, there is no response to my challenge yet. If there is(perhaps Ghent12?), I will provide more points to follow.

But again, you could only do so much. If someone chooses to stay in the familiarity of his "cave", you will be only ridiculed for telling him that the outside is truer...;)

And suggestion to you, COW: take a rest and go to sleep. You are a programmer, so you should know that when you stuck at a piece of problematic code, it is better to go away, and sleep/play, rather than keep laboring your already exhausted brain. Have a good night.

[ThePythonicCow]

Re: Goodbye, Mr Roberts

Notice the 36% is the weight of one safety factor.

I do not understand what you say here. Please see my post #190 just above for my explanation of that 36% number.

I do not think "safety factor" is a factor in Chandler's analysis. If the safety factor had been exactly ZERO (the next sparrow to land on the roof would have brought the entire tower down) Chandler's analysis still holds. At ZERO safety factor, the lower portion provides sufficient upward force to hold the upper, but cannot take any additional weight.

In the instant before general collapse began, the lower portion, below the impact zone, was undamaged (according to the official story.) Certainly the lower portion was at least still providing 100% or more of the load capacity required to support the top, prior to collapse.

During the time period analyzed by Chandler the (heretofore supposedly undamaged) lower portion was not providing supporting load; it was providing only 36% of supporting load. But it was not damaged by impact from the upper portion at anytime during or prior to this analyzed time interval, as can be directly observed from the motion of the upper portion, which did not decelerate at any point during or prior to this interval.

Impact imparts a force which alters the velocity of a mass. At no time did the lower portion impart a force to (hence receive a force from either) the upper portion greater than the usual static load. Throughout the analyzed time period during the general collapse, the lower portion imparted substantially less, not even the same, force as the usual static load it had been supporting.

36% / 3 = 12%, now meaning the 88% of strength of lower section has been eliminated.

If redo the calculation with safety factor of 5:

36% / 5 = 7.2%, meaning 92.8% of strength has been eliminated.

I have no idea what you're computing here, skyson, though likely my confusion lies with my previous comment about the meaning of that 36%.

[ThePythonicCow]

Re: Goodbye, Mr Roberts

I completely understand your line of thinking, errr...surprise, surprise, because I am a "truther"!

Yeah - ain't that the truth ;).

Until I slowly discovered that many people's mind is trapped in the a virtual cave, unable to escape:

Good explanation.

Here are two fascinating articles:
Faulty Towers of Belief: Part I. Demolishing the Iconic Psychological Barriers to 9/11 Truth
Faulty Towers of Belief: Part II. Rebuilding the Road to Freedom of Reason

The author of these articles, Laurie A. Manwell, states on Page 63 of her second article that she is a PhD candidate at the University of Guelph, Canada. This is the same University at which John McMurtry works. Some of his 9/11 and related work is quite interesting. If I lived closer, I'd stop by Guelph to see if it might have a program of interest to me. It seems like it might be a good place, based at least on this sample of two.

I lay out my basic points at post #170 again. So far, there is no response to my challenge yet. If there is(perhaps Ghent12?), I will provide more points to follow.

I will re-read #170 a bit closer, confident that it is a fair reflection of your basic points. Thanks.

And suggestion to you, COW: take a rest and go to sleep. You are a programmer, so you should know that when you stuck at a piece of problematic code, it is better to go away, and sleep/play, rather than keep laboring your already exhausted brain. Have a good night.

I should warn you that I have enjoyed the same ebb and flow of energy and focus on whatever interested me for over a half-century now.

You've probably got a better chance of converting everyone on this thread to being 9/11 Truthers than you have of changing my style of work.

But I do appreciate the warm concern - thanks.

[skyson]

Re: Goodbye, Mr Roberts

I have no idea what you're computing here, skyson, though likely my confusion lies with my previous comment about the meaning of that 36%.

Chandler explained this at the later half of his article. Search for the figure of "90%".

I should warn you that I have enjoyed the same ebb and flow of energy and focus on whatever interested me for over a half-century now.

You've probably got a better chance of converting everyone on this thread to being 9/11 Truthers than you have of changing my style of work.

But I do appreciate the warm concern - thanks.

Here is an old Chinese story for you to enjoy - The Three Season Man:

One day, a man came to Confusius's home. He saw a student sweeping falling leaves at the front, and he asked this student:

"How many seasons are there in a year?"

The student said:"Four seasons".

The mans said:"No, there are only three seasons".

They argued for a long time, before they settled on a bet: they would ask the master Confusius for the answer. If the man won, the student would bow three times to the man, and if the student won, the man would bow four times to the student.

The student called the master out, and he asked him how many seasons there were in a year.

Confusius said:"Of course three seasons. No doubt about it".

The student unwillingly bowed three times to the man, and the man happily left.

After the man left, the student asked:"Master, everyone knows that there are four seasons. Why do you tell him that there are only three seasons?"

Confusius replied:"Don't you see the man is green color? He is a grasshopper. He will die at the end of autumn. How can you convince someone there are four seasons, while his whole life has only three seasons?"

Enjoy the day!;)

[c1ue]

Re: Goodbye, Mr Roberts

Quote:

Originally Posted by c1ue Yet you somehow disassociate the speed of the collapse in Delft and in the other videos I posted. Are you saying these were also demolition jobs?

I seriously doubt that Delft and Madrid were demo jobs. I have no specific timings of either of these, so don't know what such timings would show. I'd be quite surprised if they showed continuous rapid downward acceleration of downward pieces during a period of impact with heretofore undamaged lower structure.

Playing with the formula for determining the time is itself instructive:

time to fall = square root(height divided by 1/2 times gravity )

If h = 1000 feet, t = 7.9s
If h = 160 feet, t = 2.84s (Delpht)
If h = 50 feet, t = 1.76s (New York)

I think it is safe to say Delpht was not significantly over the theoretical free fall time as is the smaller building video. And these weren't demo jobs.

If non-demo jobs can approach free fall speed, why not the WTC buildings? Note Delpht - the fire started on the 6th floor (out of 13).

You failed to understand the physics presented in Destruction of the World Trade Center North (pdf) by David Chandler, linked from my post #162 above.

I read this paper, and Mr. Chandler refers to the safety margin of 3 to 5.

This in turn was referenced from a paper by T. Szamboti, "The sustainability of the controlled demolition hypothesis for the destruction of the Twin Towers"

In this referenced paper, Mr. Szamboti calculated the design stresses of the WTC via a straight compression strength calculation of steel.

So in reality the 3 to 5 came from another 9/11 truth paper - not the architects of the buildings. Said paper says about referenced safety factor:

The reader should be reminded here that the factor of safety shown for the perimeter is for when it is withstanding gravity loads only and it should be realized that the perimeter was also intended to withstand high wind and seismic loads.

Given that it is documented by the NIST that there was noticeable tilt in both WTC1 and WTC2 top floors as they collapsed - it still seems to me that failure of the lower, non-fire floors is very conceivable.

Furthermore said Szamboti paper notes, in agreement with NIST, that 9 core columns were severed in either building, but then glosses over the remaining 10 or 12 damaged columns in either building.

The report also notes a maximum temperature of 1202 degrees F when NIST notes 1832 degrees F.

Final note: the Szamboti report notes that no more than 25% of the weight capacity of the structure would be used on a normal day.

Even assuming everything Szamboti says is correct - and this cannot be assumed given the provenance of the paper, I still don't see a smoking gun.

40% of core columns destroyed outright or damaged.

50% or more strength loss from any remaining standing columns - undamaged or no.

Impact damage not evenly spread throughout the core - certainly most on one side.

Exterior columns showed visible deformation.

Slam dunk for collapse? No

Possibility for collapse? Absolutely

I still don't see a smoking gun.

As for Chandler - he makes a number of assumptions which bring his conclusion into doubt:

1) He assumes the entire force is evenly transmitted through the entire structure. This is the same error which skyson makes. The 2 parts of each WTC building are not billiard balls, there is measurable time necessary for force to transmit through each structure. This measurable time is the difference between impact and static loads - and is why a man can stand on a board but fall through it when jumping up and down.

http://www.youtube.com/watch?v=bEj5HoTWELk&NR=1

In this video, the man stands on the board and even bounces a bit. He then runs, jumps up no more than 4 feet, and breaks the board. Impact vs. Static load.

2) His second conclusion is that the speed of the fall is such that the lower structure can't be resisting. But again, the slower than maximum theoretical falling speed actually is counter to this argument: if the falling WTC floors were only slowed slightly by the lower structure - whether because a pancake or a structural collapse was caused - then either scenario dictates a slower than theoretical falling speed. A timed nano-thermite demolition is a Rube Goldberg explanation in this context.

So, still not very convincing.