WTC freefall for first 2.5 seconds? (engineer replies only please)

[Sizzler]

http://911blogger.com/node/17685

Can one of the engineers on this site please watch this video and give me your opinion.

From 9-11 blogger:

Regarding the video:
Contrary to the August 2008 NIST report on WTC7, the acceleration of Building 7 has been measured and is found to be indistinguishable from the acceleration of gravity over a period of about 2.5 seconds during the fall. Freefall indicates zero resistance. It also indicates that the energy of the falling mass is not available to do work on the lower structure (i.e. such things as breaking, bending, crushing, etc.) A video detailing the measurement process and commenting on the results is posted on the AE911Truth YouTube channel, accessible through http://www.ae911truth.org/freefall. The video responds to the recently released NIST WTC7 document.

I have two questions basically.

1. Is his analysis correct; is the building (or at least the outer shell) essentially free falling for the first 2.5 seconds? And if not, why not?

2. Is this possible without an added force to remove resistance and allow free-fall (ie, demolition of some sort)?

Could the engineers here please respond to this. Thanks.

p.s. I post this video because it appears to be lacking "woo", at least from my layman perspective.

[technoextreme]

As an engineer I can say with a 100% certainty that you can't measure acceleration using the videos.

[Sizzler]

As an engineer I can say with a 100% certainty that you can't measure acceleration using the videos.

Thanks for the reply. Could you or anyone else tell me why? I could see this being the case if one were trying to measure acceleration for a very short interval, perhaps a few points of a second. However the acceleration is measured over a period of of more that 3.5 seconds (approx) and for 2.5 seconds of that, it is measured at essentially free-fall.

Am I wrong, and if so why. Thanks in advance.

[rwguinn]

Thanks for the reply. Could you or anyone else tell me why? I could see this being the case if one were trying to measure acceleration for a very short interval, perhaps a few points of a second. However the acceleration is measured over a period of of more that 3.5 seconds (approx) and for 2.5 seconds of that, it is measured at essentially free-fall.

Am I wrong, and if so why. Thanks in advance.
In answer to why you can't measure acceleration from the video:
No accurate time reference, (frame rate can vary) no accurate (I.e., undistorted (unless you have video from straight on, perpendicular-to-the wall-at-the-same-elevation)) distance reference. A mis-measurement of as little as .05 seconds or 1 foot is significant. The time reference is also very short. Accumulated error is huge. Remember it only takes 37% longer to fall 12 feet at 1/2 g as it does at 1 g...
As far as "the energy of the falling mass is not available to do work on the lower structure ", this is true for free-falling mass.
When it hits something, e.g., the lower structure, it is no longer free falling...

[technoextreme]

Thanks for the reply. Could you or anyone else tell me why? I could see this being the case if one were trying to measure acceleration for a very short interval, perhaps a few points of a second. However the acceleration is measured over a period of of more that 3.5 seconds (approx) and for 2.5 seconds of that, it is measured at essentially free-fall.

Am I wrong, and if so why. Thanks in advance.
Well because of the reason why the guy gave in the movie. It's a crappy image. Even a smooth crisp .jpeg image is missing information in the image. It may not seem important in the case of the looking at pictures of dogs but when you are trying to do what the guy is doing it's dam well pretty important. It's the same reason why biomedical images are lossless versus lossy.

[Sizzler]

In answer to why you can't measure acceleration from the video:
No accurate time reference, (frame rate can vary) no accurate (I.e., undistorted (unless you have video from straight on, perpendicular-to-the wall-at-the-same-elevation)) distance reference. A mis-measurement of as little as .05 seconds or 1 foot is significant. The time reference is also very short. Accumulated error is huge. Remember it only takes 37% longer to fall 12 feet at 1/2 g as it does at 1 g...
As far as "the energy of the falling mass is not available to do work on the lower structure ", this is true for free-falling mass.
When it hits something, e.g., the lower structure, it is no longer free falling...

Thanks for the reply, that makes sense.

Why then would NIST make any attempt to measure the acceleration of the building (or at least outer shell) of it, if it is an inaccurate measurement anyway? I am assuming they used the video to determine their own interpretation of the acceleration.

[Sizzler]

Well because of the reason why the guy gave in the movie. It's a crappy image. Even a smooth crisp .jpeg image is missing information in the image. It may not seem important in the case of the looking at pictures of dogs but when you are trying to do what the guy is doing it's dam well pretty important. It's the same reason why biomedical images are lossless versus lossy.

I will direct post 6 at you as well. Thanks in advance.

[rwguinn]

Thanks for the reply, that makes sense.

Why then would NIST make any attempt to measure the acceleration of the building (or at least outer shell) of it, if it is an inaccurate measurement anyway? I am assuming they used the video to determine their own interpretation of the acceleration.
Lots of videos, access to the originals (uncompressed), from many angles--plus they had access to construction details, and a whole hell of a lot better analysts and equipment than the average troother...

[technoextreme]

Lots of videos, access to the originals (uncompressed), from many angles--plus they had access to construction details, and a whole hell of a lot better analysts and equipment than the average troother...
I completely agree with everything he said.

[ktesibios]

For original tapes, the timing accuracy of video is pretty good. Even garden variety microprocessor-grade crystal timebases out of a catalog- such as you're likely to find in a video camera typically have rated accuracies of +- 100 ppm.

For broadcast, standards are even tighter. The FCC mandates that the 3.579545 Hz color subcarrier, which the horizontal and vertical scans are locked to, be maintained to +- 10 Hz, which is +- 2.7 ppm.

Take that original recording, convert it to a streaming format and put it up on YouTube and all your assumptions about the timebase are right out the window.

[rwguinn]

For original tapes, the timing accuracy of video is pretty good. Even garden variety microprocessor-grade crystal timebases out of a catalog- such as you're likely to find in a video camera typically have rated accuracies of +- 100 ppm.

For broadcast, standards are even tighter. The FCC mandates that the 3.579545 Hz color subcarrier, which the horizontal and vertical scans are locked to, be maintained to +- 10 Hz, which is +- 2.7 ppm.

Take that original recording, convert it to a streaming format and put it up on YouTube and all your assumptions about the timebase are right out the window.
I do b;leeve that is what we were saying...

[ktesibios]

I do b;leeve that is what we were saying...

Quite so, I just thought that putting numbers to it might be worthwhile.

I spared you my tales of things **** video editors do to make sure the sound won't sync when you try to lay it back, so count yo' blessings.;)

[Sizzler]

Thanks for you replies guys.

So to sum up, streamed video does not have good enough quality to produce an accurate measurement of acceleration. Seeing as the video's author got a measurement of approximately free-fall, it is possible that the true acceleration was actually lower (obviously not higher because that would defy gravitational law).

On the other hand, original video as well as blueprints can be used to produce accurate measurements of acceleration. Thus, NIST's measurements are accurate because they would have access to such resources.

Is this layman summary correct?

I have a few more questions but I don't have time at the moment to answer them.

Thanks again.

[Newtons Bit]

Error approximation is something that whole chapters of some of my engineering textbooks are devoted to. Most of that is how to determine what errors you have and if they are significant.

The problem with the experiment that this "truther" did is that there is no way to tell what, if any, the error is. The reason is because it is an analysis based on one data source. If there is an error in his data source, not only will he get an inaccurate result, he'll not know it. This I hope is obvious.

The reason why NIST is much more accurate is that they used more data sources. Multiple different cameras/camera angles can be averaged together. You can do a statistical analysis to determine if the individual results of each data source is just gibberish or if they're clustered around something that might be correct.

[gumboot]

Thanks for you replies guys.

So to sum up, streamed video does not have good enough quality to produce an accurate measurement of acceleration.



This is only part of the problem. Another is resolution. For any given image your margin of error is 1 pixel - so if the building's size scale is 10ft for 1 pixel, your margin of error is 10ft. To further complicate it, due to perspective, a given pixel scale only applies at a given distance from the camera, with any variation in distance causing a change in resolution scale. So this further affects your margin of error.

Then with highly compressed streaming video pixel fidelity from the original is incredibly poor (hence that blocky look) so you're adding increased margin of error because you can't even be certain that pixel X is actually where it appears to be at frame Y.

It's notable that in the video the commentator totally glosses over the process of establishing positions on the building, and any reference to image resolution. These are, in fact, the most important steps.

Dismissing the variation in his results with that of acceleration due to gravity (less than 1% variation) as due to image resolution is total nonsensical and meaningless because he has not established what the resolution margin of error is.

Without have the video he used, making any sort of assessment is futile.

[Sizzler]

Error approximation is something that whole chapters of some of my engineering textbooks are devoted to. Most of that is how to determine what errors you have and if they are significant.

The problem with the experiment that this "truther" did is that there is no way to tell what, if any, the error is. The reason is because it is an analysis based on one data source. If there is an error in his data source, not only will he get an inaccurate result, he'll not know it. This I hope is obvious.

The reason why NIST is much more accurate is that they used more data sources. Multiple different cameras/camera angles can be averaged together. You can do a statistical analysis to determine if the individual results of each data source is just gibberish or if they're clustered around something that might be correct.

So if this truther analyzed several data sources instead of just one, and still found in all cases that the first 2.5 seconds were 1% (or near that) slower than gravitational free-fall acceleration, would that be enough to reasonably conclude that that was the acceleration?

Also I ask your opinion on something else. What are your comments on NIST's use of only 2 data points (one of which beginning before sudden decent) when calculating acceleration and then concluding that acceleration was constant for the visible portion of collapse? (my words may be wrong here but it is all in the video as you know).

Do you consider,

1. It a reasonable way to estimate an accurate acceleration rate for the decent of the building?

2. It as sloppy work but not that big of a deal?

3. It to indicate incompetence or perhaps deliberate masking of an issue?

ETA: I am actually directing this question at anyone. (although Newtons Bit your explanations are quite clear.)

[beachnut]

http://911blogger.com/node/17685

Can one of the engineers on this site please watch this video and give me your opinion.

From 9-11 blogger:


I have two questions basically.

1. Is his analysis correct; is the building (or at least the outer shell) essentially free falling for the first 2.5 seconds? And if not, why not?

2. Is this possible without an added force to remove resistance and allow free-fall (ie, demolition of some sort)?

Could the engineers here please respond to this. Thanks.

p.s. I post this video because it appears to be lacking "woo", at least from my layman perspective.
1. Why not check it yourself. Why ask, why not say; look I got this, do you think I am right? Free fall. Just what do you expect the time to be after you check his work? How do you account for errors in your estimation. If you waste much more time on 9/11 truth, you will be upset you could have earned a PhD in engineering in the last 7 years instead of being fooled by liars in 9/11 truth. What is you take on the speed of fall, and why? Most people here can figure this out with a grade school education and research.

What did your estimate say about the video? Did you check it yourself? When you first started posting you seem to trust the lies of 9/11 truth first, and then you back in the knowledge and engineering to understand.

2. There were no explosives or thermite. It is only possible to fall at a velocity as gravity works on it. If you notice the interior, as evidence by the Penthouse falling 6 to 8 second before the facade, is damaged and not holding up the building any more. And the what looks like a nice straight down fall is actually all messed up and bent.

Yes, the fall was faster due to the fact the interior support was totally gone when the façade fell. This was due to fire, more powerful than TNT. No explosives, you would hear them, no thermite, it so stupid it hurts to think of the thermite guys cutting into the wall as it would also be with explosives.

The speed of free fall is the sign of woo! The video used would not even give you the accuracy to see if it is as fast as free fall, we are talking 5, 10 or 20 percent time differences alone, and the ability to see the start of movement is impossible. This is .25 .5 or .125 second difference. Go ahead time it. What about modeling the camera lens errors? The timing errors? Frames per second? Camera timing?

LOL, that is dumb. His video has enough error to mask the 5 to 20 percent less than free fall time. What a dolt.

There is nothing holding up the building at this time of falling. If you add the penthouse section which disappears before this video cheery picking, you have too much time. You must use the time of the initial fall. He also leaves out the small movement tie at the beginning. So he is only trying to make up a lie.

The rate of fall is slowed, he is unable to measure it. Funny how much time these guys waste being apologist for terrorist. Pathetic. Can't find evidence, make up more lies.

Go to school, so in the next 7 years you can tell them they are full of crap.


This guy is the worse kind of liar. He ignores the fact the interior is all but gone when the façade falls! Failure and lies, we can add another biased teacher to the list who apologize for terrorists.

This liar must add the falling penthouse into his time, or explained that is the reason there is little resistance. What a dolt. He ignores the potential energy and the acceleration of gravity. Sad when a teacher is making up lies to support liars.

1 percent is significant. What a dolt. His own presentation proves his ideas false. He stops at 2.5 seconds cause his little study starts to show "resistance". LOL The error in his start time, the first inches of movement can't be seen, so his timing is not correct.

He is not close enough to see the first movement, so that .125 second missing is proof of slower than freefall due to the façade resistance.

Errors. He times only a section of the fall! This means he ignores the time as it starts to move slowly, he just waves his liar hands and ignores almost a second, or .5 second of falling as the façade false apart below, he ignores the first .5 second of falling, which means the time is 20 percent slower than freefall. BUSTED! You can't pick the sections that are close to freefall and ignore the TONS of facade breaking the connections in that first .5 second of constant speed fall! Velocity constant, then it falls again. LIAR guy is so calm as he lies.


The very thing he is saying, he is ignoring. He is saying there is no resistance. He ignores the .5 to .75 seconds showing resistance, and draws his line. Cherry picking failed science teacher.
Debunked by his own fraud timing.

[Sizzler]

1. Why not check it yourself. Why ask, why not say; look I got this, do you think I am right? Free fall. Just what do you expect the time to be after you check his work? How do you account for errors in your estimation. If you waste much more time on 9/11 truth, you will be upset you could have earned a PhD in engineering in the last 7 years instead of being fooled by liars in 9/11 truth. What is you take on the speed of fall, and why? Most people here can figure this out with a grade school education and research.

What did your estimate say about the video? Did you check it yourself? When you first started posting you seem to trust the lies of 9/11 truth first, and then you back in the knowledge and engineering to understand.

2. There were no explosives or thermite. It is only possible to fall at a velocity as gravity works on it. If you notice the interior, as evidence by the Penthouse falling 6 to 8 second before the facade, is damaged and not holding up the building any more. And the what looks like a nice straight down fall is actually all messed up and bent.

Yes, the fall was faster due to the fact the interior support was totally gone when the façade fell. This was due to fire, more powerful than TNT. No explosives, you would hear them, no thermite, it so stupid it hurts to think of the thermite guys cutting into the wall as it would also be with explosives.

The speed of free fall is the sign of woo! The video used would not even give you the accuracy to see if it is as fast as free fall, we are talking 5, 10 or 20 percent time differences alone, and the ability to see the start of movement is impossible. This is .25 .5 or .125 second difference. Go ahead time it. What about modeling the camera lens errors? The timing errors? Frames per second? Camera timing?

LOL, that is dumb. His video has enough error to mask the 5 to 20 percent less than free fall time. What a dolt.

There is nothing holding up the building at this time of falling. If you add the penthouse section which disappears before this video cheery picking, you have too much time. You must use the time of the initial fall. He also leaves out the small movement tie at the beginning. So he is only trying to make up a lie.

The rate of fall is slowed, he is unable to measure it. Funny how much time these guys waste being apologist for terrorist. Pathetic. Can't find evidence, make up more lies.

Go to school, so in the next 7 years you can tell them they are full of crap.


This guy is the worse kind of liar. He ignores the fact the interior is all but gone when the façade falls! Failure and lies, we can add another biased teacher to the list who apologize for terrorists.

This liar must add the falling penthouse into his time, or explained that is the reason there is little resistance. What a dolt. He ignores the potential energy and the acceleration of gravity. Sad when a teacher is making up lies to support liars.

1 percent is significant. What a dolt. His own presentation proves his ideas false. He stops at 2.5 seconds cause his little study starts to show "resistance". LOL The error in his start time, the first inches of movement can't be seen, so his timing is not correct.

He is not close enough to see the first movement, so that .125 second missing is proof of slower than freefall due to the façade resistance.

Errors. He times only a section of the fall! This means he ignores the time as it starts to move slowly, he just waves his liar hands and ignores almost a second, or .5 second of falling as the façade false apart below, he ignores the first .5 second of falling, which means the time is 20 percent slower than freefall. BUSTED! You can't pick the sections that are close to freefall and ignore the TONS of facade breaking the connections in that first .5 second of constant speed fall! Velocity constant, then it falls again. LIAR guy is so calm as he lies.


The very thing he is saying, he is ignoring. He is saying there is no resistance. He ignores the .5 to .75 seconds showing resistance, and draws his line. Cherry picking failed science teacher.
Debunked by his own fraud timing.

I only reply to you when I skull f'd drunk. Reply Reply.

[beachnut]

I only reply to you when I skull f'd drunk. Reply Reply.
The idiot shows the work to debunk him. Sorry, I left in a lot of notes and thoughts, too bad I had to watch the video, you can't read my post, I watched your dumb video OP subject woo piece.

As an engineer I watched his video, and caught his major error. As I have always been upset with idiots who fail to time the beginning of the fall, the first few inches. This idiot actually presents the first .75 seconds which he dumps.

I am tried of terrorist apologist, the video author, who actually shows his errors.

Do you lack the ability to see he is a liar? He ignores the first .75 second showing resistance and constant velocity, then he draws his line on the section closer to acceleration of gravity. Then he has to stop again, because it shows resistance, and he never mentioned the first 8 seconds of building falling.

He is a fraud. You can't see it; are you saying you can't think right until you are drunk.

As an engineer, his work is biased, but anyone can see if they look, he is debunked by his own work and words.

[beachnut]

http://911blogger.com/node/17685

Can one of the engineers on this site please watch this video and give me your opinion.

From 9-11 blogger:


I have two questions basically.

1. Is his analysis correct; is the building (or at least the outer shell) essentially free falling for the first 2.5 seconds? And if not, why not?

2. Is this possible without an added force to remove resistance and allow free-fall (ie, demolition of some sort)?

Could the engineers here please respond to this. Thanks.

p.s. I post this video because it appears to be lacking "woo", at least from my layman perspective.
1. NO.
2. The building fell at a speed consistent with gravity after internal failures due to fire. The dolt left out the initial resistance to come up with his lie.

After watching the video a few times to catch the lie, I left my posts unedited and full of junk, just like the video.

I am an engineer, you asked for a response; but a grade school education can find the error in this failed attempt to propel the lies of A&E dolts.

[Pantaz]

Beachnut,
Turn off the computer... go outside, smell some flowers... watch the birds flying... pet a dog... and forget the myopic "truthers" for a while.

[Sizzler]

So if this truther analyzed several data sources instead of just one, and still found in all cases that the first 2.5 seconds were 1% (or near that) slower than gravitational free-fall acceleration, would that be enough to reasonably conclude that that was the acceleration?

Also I ask your opinion on something else. What are your comments on NIST's use of only 2 data points (one of which beginning before sudden decent) when calculating acceleration and then concluding that acceleration was constant for the visible portion of collapse? (my words may be wrong here but it is all in the video as you know).

Do you consider,

1. It a reasonable way to estimate an accurate acceleration rate for the decent of the building?

2. It as sloppy work but not that big of a deal?

3. It to indicate incompetence or perhaps deliberate masking of an issue?

Bumped for any of the engineers. Seems the mods at 9-11 blogger aren't willing to post any skepticism.

[TjW]

Your question has already been answered by Newton's Bit and gumboot in posts 14 and 15.
Science is, by its nature, reproducible.
So, given adequate data, in the sense of multiple videos of adequate resolution (both pixel and timing), a knowledge of the placement of the cameras and the optics involved, accurate measurements of visible points on the buildings from the "as-built" plans, the NIST results could be duplicated. Anyone competent to do so would also be able to supply the error bars on their estimate and why they are there.

OTOH, for a rough-and-ready estimate, you could look at the pictures up to about 2 1/2 seconds after they began and notice the relationship between the stuff that first fell off the tower and where stuff is falling off now (the collapse zone).
If there was one percent or less difference between the collapse and a free fall acceleration, the collapse zone and the first pieces would be at virtually the same altitude. They're not. The collapse zone is much higher. I really don't expect you to honestly answer this question, but what does that tell you about the acceleration of the collapse relative to free fall?

[GregoryUrich]

Bumped for any of the engineers. Seems the mods at 9-11 blogger aren't willing to post any skepticism.

Siz,

I have seen at least two of David Chandler's previous analyses that have serious problems and misunderstandings that negate his conclusions. I haven't looked at this analysis, but after the previous two, I'm not willing to spend time on it.

Dr. Greening, Einsteen and OneWhiteEye are working on this issue here (http://the911forum.freeforums.org/withering-critique-of-the-new-wtc7-report-t44-105.html). Their approach seems to be reasonable and I know Dr. Greening is quite careful. Their initial results indicate a fairly constant acceleration for the first 3-4 seconds of around 8.75m/s^2.

[Sizzler]

Your question has already been answered by Newton's Bit and gumboot in posts 14 and 15.
Science is, by its nature, reproducible.
So, given adequate data, in the sense of multiple videos of adequate resolution (both pixel and timing), a knowledge of the placement of the cameras and the optics involved, accurate measurements of visible points on the buildings from the "as-built" plans, the NIST results could be duplicated. Anyone competent to do so would also be able to supply the error bars on their estimate and why they are there.

OTOH, for a rough-and-ready estimate, you could look at the pictures up to about 2 1/2 seconds after they began and notice the relationship between the stuff that first fell off the tower and where stuff is falling off now (the collapse zone).
If there was one percent or less difference between the collapse and a free fall acceleration, the collapse zone and the first pieces would be at virtually the same altitude. They're not. The collapse zone is much higher. I really don't expect you to honestly answer this question, but what does that tell you about the acceleration of the collapse relative to free fall?

Thanks for your reply in the first paragraph.

As for the question you asked me in the third paragraph, I have a suspicion you are referring to the collapses of WTC1/2, although you don't specify. OP is discussing WTC7.

[Sizzler]

Siz,

I have seen at least two of David Chandler's previous analyses that have serious problems and misunderstandings that negate his conclusions. I haven't looked at this analysis, but after the previous two, I'm not willing to spend time on it.

Dr. Greening, Einsteen and OneWhiteEye are working on this issue here (http://the911forum.freeforums.org/withering-critique-of-the-new-wtc7-report-t44-105.html). Their approach seems to be reasonable and I know Dr. Greening is quite careful. Their initial results indicate a fairly constant acceleration for the first 3-4 seconds of around 8.75m/s^2.

Thanks Greg. for your reply.

Dr. Greening is a better source in my opinion too. Thanks for the link; I will check it out right now.


Cheers