9/11 Physics from Non-Experts

[rwguinn]

Uh, how many demolition companies manufacture their own explosives or get them delievered in the mail anyway?

And how do they access those portions of the building? How long does it take to remove the fire protection? How long to install the explosives on just the right columns in just the right places? How long to ensure all the wiring and detonators are done correctly? Any estimates? Or are you again assuming this is something that can be knocked off in ten minutes because it doesn't sound complicated?

(I'd also ask how these planted explosives were shielded from damage after the jets impacted the buildings, how these explosives were shielded from the resulting heat and fires, how the jets managed to crash into each WTC tower at just the right location as to match were these explosives were planted. But I'll leave those questions out for now.)

Why do you assume this? It looks like the old "it doesn't look complicated to do therefore it must not be complicated to do" bug raising its head again.

One might conclude from this statement that knocking a building down with explosives is a relatively easy task that anybody can do without much trouble. Is that what you are saying?

But only if it as uncomplicated and easy to do as you think it is. Again, I point out that you are assuming it would be as easy to do as you make it out to be. Reality tends not to to work that way and things are often more involved or complicated than it might seem on the surface.

Interesting, but none of that has anything to do with working with explosives, nor their handling and installation for the purposes of destroying buildings. If I wanted to ask about working with software systems, then it seems you'd be the guy to ask.

Except you are assuming, without providing any evidence, that such installation would be simple and easy to do.

No, I am saying you are underestimating the complexity of the steps involved.

Simple question to illustrate the point: that twenty or thirty page full-colour flyer you get in your mailbox from Sears or whichever, how many days in advance do you think that flyer was first created? A week? Two weeks? A month? What steps do you think are needed to create a publication like that which 99% of people probably throw out as soon as they get it?

Actually, I have to side with GregoryUrich here--
If the intent was simply to bring down the building, no long lead time was needed--just a half-dozen dedicated idiots with sufficient C4 to blow away about 60-75% of the columns on an individual floor, and enough time to slap them on and set them off- Individual timers, whatever.
Somebody might have noticed a few guys bringing in that much C4, and the booms would have been quite noticeable from some distance away.
The planning and time it takes for CD are merely for safety reasons--to make sure the thing falls where and when you want it to.
To simply bring it down is a lot easier, and quicker. But as many, many others and I have said, someone probably would have noticed

 

[GregoryUrich]

Thanks GregoryUrich.

They seem to be using the metric system throughout. 566,000 short tons make 513,600 metric tons (or tonnes). What do you refer to as specific gravities? I'd like to look further into this.

"Specific gravity" is Bazant's terminology for density over the height of the building. This is Bazant et al.'s latest:

http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/00%20WTC%20Collapse%20-%20What%20Did%20%26%20Did%20Not%20Cause%20It%20-%205-2007.pdf

 

[GregoryUrich]

Uh, how many demolition companies manufacture their own explosives or get them delievered in the mail anyway?

...

Simple question to illustrate the point: that twenty or thirty page full-colour flyer you get in your mailbox from Sears or whichever, how many days in advance do you think that flyer was first created? A week? Two weeks? A month? What steps do you think are needed to create a publication like that which 99% of people probably throw out as soon as they get it?

You are the one comparing this to flyers.

Here's an introduction video from The Orica Group. By the way, it's even simpler than I thought it was:

http://www.i-konsystem.com/html2/digitalrevolution.html

 

[Carefulplease]

"Specific gravity" is Bazant's terminology for density over the height of the building. This is Bazant et al.'s latest:

http://www.civil.northwestern.edu/people/bazant/PDFs/Papers/00%20WTC%20Collapse%20-%20What%20Did%20%26%20Did%20Not%20Cause%20It%20-%205-2007.pdf

This is indeed the paper I was referring to earlier. The term they use is "specific mass". I don't see how you get to 513 tonnes. What values for k_0 and k_2 do you use? The graph in fig. 1 makes it plain that the small correction from the non-linear part of the variation makes very little difference. Assuming 22m bathtub depth as in fig. 3, and 415m above ground, I obtain a value that is very close to 500,000 tonnes. I don't see that they contradict themselves.

 

[GregoryUrich]

This is indeed the paper I was referring to earlier. The term they use is "specific mass". I don't see how you get to 513 tonnes. What values for k_0 and k_2 do you use? The graph in fig. 1 makes it plain that the small correction from the non-linear part of the variation makes very little difference. Assuming 22m bathtub depth as in fig. 3, and 415m above ground, I obtain a value that is very close to 500,000 tonnes. I don't see that they contradict themselves.

Here's what I did (assuming linear in top part):

avg spec mass top part (1 035 000 kg/m) x 29 floors x 3,7m = 134 032 500 kg
avg spec mass bot part (1 255 000 kg/m) x 87 floors x 3,7m = 403 984 500 kg

Total = 515 040 000 kg = 567 725 tons

Bazant says the mass was "close to 500,000 tons". Everyone I have discussed this with here interprets "tons" as short tons and "tonnes" as metric. That is why I say they contradict themselves. Maybe they meant tonnes, but either way they are way off the mark. The actual in-service weight was probably less than 300,000 short tons.

 

[jaydeehess]

Actually, I have to side with GregoryUrich here--
If the intent was simply to bring down the building, no long lead time was needed--just a half-dozen dedicated idiots with sufficient C4 to blow away about 60-75% of the columns on an individual floor, and enough time to slap them on and set them off- Individual timers, whatever.
Somebody might have noticed a few guys bringing in that much C4, and the booms would have been quite noticeable from some distance away.
The planning and time it takes for CD are merely for safety reasons--to make sure the thing falls where and when you want it to.
To simply bring it down is a lot easier, and quicker. But as many, many others and I have said, someone probably would have noticed

It seems to be the contention though, among many CT theorists, that the towers were indeed dropped deliberatly such that damage is confined mostly to the WTC complex, that one of the 'anomolies' is that the building did not topple at the initial collapse point, and that this is one indication of CD.

GU may not subscribe to such nonsense, but many do.

 

[tsig]

Therein lies the problem with your assessment. When one is not familiar with all the various technical aspects of a particular industry or occupation, it is easy, and perhaps even natural, to greatly oversimplify the tasks actually required by that industry/occupation.

I'm confident, for example, the average layperson who has no experience with how things are printed and published probably thinks those annoying flyers you get in your mailbox from a major retail chain are no big deal to create either. In reality, it's a large industry and a significant undertaking involving a lot of technical aspects.

Yes I have noticed that the less I knew about something the easier it was to do.

Until I tried to do it.

 

[Carefulplease]

Here's what I did (assuming linear in top part):

avg spec mass top part (1 035 000 kg/m) x 29 floors x 3,7m = 134 032 500 kg
avg spec mass bot part (1 255 000 kg/m) x 87 floors x 3,7m = 403 984 500 kg

Total = 515 040 000 kg = 567 725 tons

Bazant says the mass was "close to 500,000 tons". Everyone I have discussed this with here interprets "tons" as short tons and "tonnes" as metric. That is why I say they contradict themselves. Maybe they meant tonnes, but either way they are way off the mark. The actual in-service weight was probably less than 300,000 short tons.

OK thanks. The linearity assumption easily account for the 15,040 tonnes difference. I am pretty sure they meant to refer to 1000kg "tons". They refer to kilograms in the very same sentence. Their estimate may be high but there is no contradiction.

 

[Corsair 115]

Actually, I have to side with GregoryUrich here--
If the intent was simply to bring down the building, no long lead time was needed--just a half-dozen dedicated idiots with sufficient C4 to blow away about 60-75% of the columns on an individual floor, and enough time to slap them on and set them off- Individual timers, whatever.

Okay, I'll defer to you on this - if one is going to take a purely blunt force approach. But as you yourself noted, it'd involve a lot of explosives and the sound of those going off would have been unmistakable.

And as jaydeehess noted, CTers often contend the collapse of the towers was too precise to be anything other than some form of controlled demolition. If it's controlled, then it's not just a matter of stuffing the relevant parts of the building with explosives.

(There's still the question of how those explosives survived the impact of the aircraft and the subsequent fires.)

Here's an introduction video from The Orica Group. By the way, it's even simpler than I thought it was:

http://www.i-konsystem.com/html2/digitalrevolution.html

You perhaps should have read that site more closely. From its FAQ page (emphasis added):

1.5 How well does the i-kon™ System work?

Extensive global applications of the i-kon™ System have demonstrated unsurpassed performance and benefits delivery in surface metal mining, quarrying & construction, demolition, open cast coal, as well as varied underground operations.

I would submit to you that there's a world of difference between using blasting to open up rockfaces in a quarry and using blasting within the restricted confines of a steel and concrete building structure in terms of the preparation time needed to ensure the job is done as desired.

 

[Apollo20]

Carefulplease:

I do believe that an assumed value of 58,000 tonnes for the upper section of WTC 1 may be a little high. However, the collapse time is relatively insensitive to the mass of the upper section which is much more dependent on what I call E1.

 

[Carefulplease]

Carefulplease:

I do believe that an assumed value of 58,000 tonnes for the upper section of WTC 1 may be a little high. However, the collapse time is relatively insensitive to the mass of the upper section which is much more dependent on what I call E1.

Thank you Apollo20,

This, I find surprising. I agree that collapse time is insensitive to mass when E1 = 0. This is because it then only deviates from free fall time owing to momentum transfer. And "resistance" from momentum transfer is not dependant on total mass. Moreover, momentum transfer has overall a much more important effect on collapse time than structural resistance (E1/unit height) has.

However, momentum transfer is very much dependent on mass distribution over height. I would thus expect variations in mass distribution (near the impact zone) to have effects at least comparable to effects from variations in E1, at least for the acceleration during the first few seconds of the collapse.

(Edited to replace "near the top" with "near the impact zone")

 

[Jonnyclueless]

Another very good point. Basically the only way to accomplish this would be to strip the walls and replace them with some sort of "explosive" drywall. And then there is the issue of making it happen sequentially. Oh, and making sure the "explosive drywall" was installed only on the floors below the impact point. I'm not trying to be a donkey about this either, i'm just trying to apply some logic .

Have you considered that maybe they were being given explosive office supplies? Apparently they had switched office suppliers just weeks before 9/11 with ties to zionists.

Those weren't your every day pens and whiteout. Oh sure it looked like toner.


OK, just wanted to get a first post out of the way and help people think outside the box and in the yard next to the house that the box was delivered.

 

[Furcifer]

OK, just wanted to get a first post out of the way and help people think outside the box and in the yard next to the house that the box was delivered.

Did you see my cat in that box? His name is Shrodie, he is very shy and very elusive.

 

[Jonnyclueless]

I'm not sure if this has been covered because the thread is so large. one claim I keep hearing is that NIST never tested the theory about the trusses sagging. Is this true? I could have sworn I have seen documentaries about this specific testing.

 

[Carefulplease]

Did you see my cat in that box? His name is Shrodie, he is very shy and very elusive.

I might have seen it but I'm only [modulus(psi)]^2 sure.

 

[Furcifer]

I might have seen it but I'm only [modulus(psi)]^2 sure.

What, you saw him? Oh well that changes everything...

 

[Furcifer]

I'm not sure if this has been covered because the thread is so large. one claim I keep hearing is that NIST never tested the theory about the trusses sagging. Is this true? I could have sworn I have seen documentaries about this specific testing.

On a serious note, I've never heard why NIST didn't test 60 foot trusses. For me personally, extrapolation is perfectly acceptable in these regards, but why not test full spans?

 

[Carefulplease]

I'm not sure if this has been covered because the thread is so large. one claim I keep hearing is that NIST never tested the theory about the trusses sagging. Is this true? I could have sworn I have seen documentaries about this specific testing.

Hi Jonnyclueless,

Tests were performed to see if the floor assemblies were compliant with the ASTM E 119 standard for fire resistance. These tests were performed on fire-insulated trusses. They did sag. Some failed to get a two-hour rating.

http://wtc.nist.gov/NISTNCSTAR1-6B.pdf

 

[Carefulplease]

On a serious note, I've never heard why NIST didn't test 60 foot trusses. For me personally, extrapolation is perfectly acceptable in these regards, but why not test full spans?

They did perform tests on full-scale short-span (35 feet) trusses. The largest furnaces available to perform fire tests were those of Underwriters Laboratories of Canada in Toronto. They were able to verify the effects of scale through comparing the results for both full-scale and half-scale tests. To build a 60 feet furnace would have been expansive and would have provided diminishing returns.

 

[Gravy]

On a serious note, I've never heard why NIST didn't test 60 foot trusses. For me personally, extrapolation is perfectly acceptable in these regards, but why not test full spans?

They say there were no facilities large enough to handle the 60-foot spans.