Merged Discussion of femr's video data analysis

[W.D.Clinger]

Pgimeno, I understand that you sincerely believe this.

Is there anyone else besides Pgimeno that sees this acceleration profile for a large building to be normal and expected?

Yes.

On 10 July 2010, in "The physics toolkit" thread, I wrote:

Abstract: The corner's downward acceleration of greater than 1g at the beginning of its descent is just what you'd expect from the physics.

For several days prior to that, I had been repeating the same mistake Dr Frank Greening made in 2008 and Major_Tom's been repeating ever since:

I have to retract this statement:

For example, we know that downward accelerations greater than 1g are physically implausible.

That isn't true in this case, because the corner being tracked is not the roof's center of gravity.

Looking at the YouTube video femr2 cited, I see that the corner did not begin its descent until some time after the opposite side of the building had already fallen some distance and built up downward velocity. The means the roof's center of gravity began its descent before t=4.871538205, and the roof had rotated during that descent.

Taking a idealized view of the situation, let's assume the roof's rotation ends abruptly at t=4.871538205, and the corner's downward component of velocity (from that time onward) is equal to the downward velocity for the roof's center of gravity. That implies a very large downward acceleration for the corner at t=4.871538205 as its velocity rises rapidly from zero to match the velocity of the roof's center of gravity, to which the corner is still attached. If you spread that acceleration over the first two seconds, say, you'll get accelerations that look like what you see in femr2's data and in tfk's graphs.

In short: The corner's downward acceleration of greater than 1g at the beginning of its descent is just what you'd expect from the physics.

It's often hard to tell what femr2 is thinking or saying, but he may have figured it out also.

Myriad figured it out nearly two years ago:

I suggest attachment to the core could be the primary factor.

Attachment to the core could explain numerous behaviours.

And I agree completely.

From nearly two years ago: http://www.internationalskeptics.com/forums/showthread.php?postid=4912626#post4912626

So, having established that something that's attached to something that's already falling may accelerate faster than g, I re-examined the available information on building 7 and found considerable evidence that the wall in question was indeed attached to other parts of the building, and that other parts of the building did indeed begin falling first.

Therefore, I conclude that a brief period of free fall or even faster than free fall acceleration of a portion of a building experiencing progressive collapse, while it might be an unusual phenomenon, is not unexpected or unexplainable given the known circumstances.

It seems to have been a very long run for a very short slide,* but as long as we got there eventually I guess I shouldn't complain.

Respectfully,
Myriad

 

[Major_Tom]

Again, you are just telling a nice story and calling it physics. Where on earth have you seen another example of this range of accelerations?

A good place to start is with known demolitions. Many. many demolitions for years. Scientists like Drs Yarimer and Lapa studying them. Many on film.

They provide the perfect laboratory to put your story to the test.


Using this large body of knowledge, please show me a single case of something in the ballpark of this acceleration range.

And if you cannot it shows you are just telling a story to fool yourself and others.

You spend so much time looking for patchwork justifications for your story that you forget to do any fact-checking or follow-up study at all.

 

[DGM]

Again, you are just telling a nice story and calling it physics. Where on earth have you seen another example of this range of accelerations?

What are you saying? Are you saying femr2 is wrong, the whole thing never happened or forces not bound to the laws of physics were in play?

Let's start here. Do you agree WTC7 was in fact on earth (specifically. NYC, USA)?

 

[ozeco41]

What are you saying? Are you saying femr2 is wrong, the whole thing never happened or forces not bound to the laws of physics were in play?

Let's start here. Do you agree WTC7 was in fact on earth (specifically. NYC, USA)?

For some strange reason working inwards (downwards if you prefer) from the big picture doesn't seem to compute for a surprisingly large number of people.

...but let's see how you go.

For the record I agree.

 

[Major_Tom]

Of course not. Femr has the only data I trust to date.

I am obviously saying you should perform reality checks to make sure you are not telling yourselves convenient stories.

Like how this acceleration profile is normal and expected. By what standards? None. Because you want to believe with no further checking.

Any examples of this early acceleration range in even known demos? The follow-up study by Frank Greening didn't reveal any. Has anyone in this forum found an example in the last few years?

Probably not. So by what standard? Mutual convenience?

 

[beachnut]

Again, you are just telling a nice story and calling it physics. Where on earth have you seen another example of this range of accelerations? ...

Here is a model of how things fall faster than g. I know you hate models, engineering and physics, but here we go again.




How does femr's analysis support your claims the gravity collapse is an illusion?

 

[NoahFence]

Why do we put so much stock in what happened previously, to compare to something that's NEVER happened before?

 

[carlitos]

Without use of the quote function, it is impossible to know what MT's "of course not" refers to.

 

[Major_Tom]

WDC: "In short: The corner's downward acceleration of greater than 1g at the beginning of its descent is just what you'd expect from the physics. "

How about what is actually witnessed with a real building as seen in many filmed demolitions?

What about in any real case? What about if people intentionally demolish a building?

You do not have to reinvent the wheel and guess an answer. It is very convenient not to look for any examples. This way you can tell a story that is subject to no reality checks.

You determine normal and expected by looking other examples. If you have no other examples how normal is it?

 

[Major_Tom]

Compared to the research of Framk Greening what you do in this forum is a cartoon. Thanks for the great example. Beachnut.

 

[carlitos]

If you have no other examples how normal is it?

In the case of Johnny Van der Meer pitching 2 consecutive no-hitters, not very normal. But it happened.

In the case of a rotating object falling with parts of that object accelerating at faster than g, there have been about a dozen examples that you have ignored.

 

[Major_Tom]

WD Clinger, here is a reproduction of a post I wrote a day or 2 after Frank Greening posted the original NIST curve:

Just to finish a point:

It is easy to graphically see how the building resists collapse as a function of time.


Taking Einsteens graph of a(t) above and remembering that this is the same as the magnitude of F(g)-F(c) (same shape with a different scale), and knowing that F(g) is constant....


We can see the shape F(c) takes just by flipping Einsteens graph upside down. In other words, just mirroring Einsteen's graph around any line a= constant for all t shows us the exact shape of the graph of how the sum total of the forces within the building resist collapse over time.

It crossed F(c)= 0 at two points: The two moments of time when a=g. And when t=0, F(c)=F(g).


If you imagine Einsteen's graph flipped upside down, you can see how building resistance held pretty well during the first few moments and then dropped like a roller coaster.


The sum total of building resistance quickly drops to absolute 0 and than some. F(c) strangely temporarily dips into the negative, baffling adherents of the Newtonian physical world view the world over.

But in our simplified model, We suspect that F(c) has at least two separate recognizable components

F(c)= F(r) + F(s)

Where the vector F(r) is the general resistance of the building to being crushed

and F(s) is a transcient spring force directed downwards.


the vector F(r) always acts upwards because it is inherently resistive.

The vector F(s) only acts downwards and is only considered to exist during a certain interval of the collapse, peaking as a(t) peaks (hence transient).

So, as vectors, they cancel one another.


We can then graphically see how the building resistance then increases rapidly, reaching a point of peak resistance. But then, yet again, resistance to crushing seems to weaken.


The confusion over an F(c) temporarily pulling the building downwards is in not recognizing it is not a purely resistive force.

The negative number may just mean that, when the "spring" was fully loaded, the magnitude of F(s) exceeded that of F(r). It doesn't mean F(r) completely disappears.

>>>>>>>>>>>

Posted in 2008 here. That took us about 2 days. It is not hard to understand the physics.


But you are still missing the point that real buildings are not observed in this range, even while being intentionally demoed.

 

[Oystein]

...
How about what is actually witnessed with a real building as seen in many filmed demolitions?

What about in any real case? What about if people intentionally demolish a building?
...

You seem to imply: If building intentionally demolished, then no freefall.

Formally:
A -> not C
with A = "intentional demolition" and C = "freefall"
Now, we could put
B = not C = "not freefall"
and
not B = not (not C) = "not not freefall" = freefall

Let's apply the Modus Tollens of Propositional Logic, which goes like this:

((A -> B) and not B) implies not A​

Here:

(("intentional demolition" -> "not freefall") and "freefall") implies "not intentional demolition"​

MT, the logic at the base of your post would prove, with mathematical precision, that WTC7 was not intentionally demolished because it exhibited freefall, which intentional demolitions never do.

Do you agree?

 

[Major_Tom]

You seem to imply: If building intentionally demolished, then no freefall.

Formally:
A -> not C
with A = "intentional demolition" and C = "freefall"
Now, we could put
B = not C = "not freefall"
and
not B = not (not C) = "not not freefall" = freefall

Let's apply the Modus Tollens of Propositional Logic, which goes like this:

((A -> B) and not B) implies not A​

Here:

(("intentional demolition" -> "not freefall") and "freefall") implies "not intentional demolition"​

MT, the logic at the base of your post would prove, with mathematical precision, that WTC7 was not intentionally demolished because it exhibited freefall, which intentional demolitions never do.

Do you agree?

Of course not. I am saying that you cannot show similar early acceleration profiles for other buildings. It is not "normal and expected".

Simple. No need to twist it like a pretzel.

 

[Oystein]

Of course not. I am saying that you cannot show similar early acceleration profiles for other buildings. It is not "normal and expected".

Simple. No need to twist it like a pretzel.

It is not normal and expected for intentional demolitions.

That knife cuts both ways, MT. You think that freefall argues against fire-induced collapse, but it in fact argues against intentional demolition first, because that's what we have plenty of video evidence about. On a broader scope, it argues against building collapse for any reason.
Taken to its logical end, it means that building 7 did not collapse at all.
Which is of course a ridiculous proposition. The only way to get out of this obvious nonsense argument is to admit that freefall is not evidence against any initiation mode of collapse.

 

[NoahFence]

It is not normal and expected for intentional demolitions.

A distinction that needs to be drilled into truthers heads apparently.

NOTHING - not a single thing on 9/11 was normal, and should be compared to something that is.

Nothing.

 

[beachnut]

Compared to the research of Framk Greening what you do in this forum is a cartoon. Thanks for the great example. Beachnut.

Like your claim of CD, a fantasy, a cartoon like theory?

How does your claim of CD, you know you said it was an inside job so evil you think of Satan, a Satan you can't name; how does your claim the gravity collapse is an illusion dovetail with femr's analysis?

 

[Major_Tom]

It is not normal and expected for intentional demolitions.

That knife cuts both ways, MT. You think that freefall argues against fire-induced collapse, but it in fact argues against intentional demolition first, because that's what we have plenty of video evidence about. On a broader scope, it argues against building collapse for any reason.
Taken to its logical end, it means that building 7 did not collapse at all.
Which is of course a ridiculous proposition. The only way to get out of this obvious nonsense argument is to admit that freefall is not evidence against any initiation mode of collapse.

The best way to get out is to not go in. Then you are already out.

You post reflects your mind, not anything I said.

You cannot find any examples of this range of early accelerations in another building. Research on known demoltions shows a very different early acceleration.

Everything else is your invention.

 

[Oystein]

The best way to get out is to not go in. Then you are already out.

You post reflects your mind, not anything I said.

My post disects your faulty logic.
I made a formal argument using propositional logic. I entered your propositions, and the result is clear: If your premises are valid, you prove there wasn't an intentional demolition.

A different take would be this:
You argue that because something is unusual, unexpected and rare, it could not happen.
But unusual, unexpected and rare things happen all the time, every day, every second, everywhere.

And a different take still: You have made no argument from first principles that connects freefall at some point in time deep into collapse progression with the mode of initiation.

And a last take would be to ask: What then do YOU conclude from this freefall? What is it evidence for? Specifically? Spell out in concrete terms a hypothesis that satisfies your interpretation of that particular evidence!

 

[Myriad]

Of course not. I am saying that you cannot show similar early acceleration profiles for other buildings. It is not "normal and expected".

Such rapid drops might be normal and expected for intentional demolitions of buildings that are 47 stories tall -- which would be one good reason why they are never attempted!

If you're demolishing a building, you want the building to expend as much of its potential energy grinding against itself as possible. If any portion of the structure topples sideways, you want it to topple "inward" into other still-standing portions, rather than outward where it can fall free. When that's done and there's nowhere left for the rest to go but down, you want it to go straight down all at once, crushing into itself as it falls. That slows the drop.

The faster the drop, the more dust you get, the more ground tremor, the greater the chance of far-ejected debris. Abutters and neighbors hate those things, and will sue you if they cause property damage or casualties. So your job as a demolition engineer is to avoid speed, which means not allowing any portion to fall unimpeded.

For instance, you wouldn't design a demo to completely collapse the wings of a wide building downward first, leaving the center as a standing spire to then topple over by itself. Because that spire would fall too damn fast, and generate lawsuits.

Hence, the typical "implosion" -- cause the perimeters to topple inward first, and then the remaining perimeter and core to sink down together. Everything collides in the lower middle, slowing it down. (Variations exist for buildings of different shapes, for example an elongated building where one end rather than the center might be the last to go.)

The wtc7 collapse was almost the opposite of that. The part you'd normally want to go last, the lower core, dropped first. The part you'd normally want to go first, the top perimeter, went last, after the collapsing interior had overloaded or kicked out its supports. So instead of the perimeter first collapsing into the interior with a slowing effect, it was left standing alone and then got tugged down from below by the already-collapsing interior, speeding it up.

Even if it is possible to achieve something like a "normal" controlled demolition of a building that tall (which has never been demonstrated), that would certainly not be the way to do it.

So questioning why the results were different from a normal CD is like questioning why people who fall out of a plane by accident fall at a much higher average speed than people jumping out of a plane on purpose. The answers being: because people who jump out of planes on purpose use a parachute, and normal CDs use techniques designed to slow the collapse down.

Respectfully,
Myriad