The Science Forum

Was my post too long for people to read on here?

I read through most of it, but I'm not impressed by free calculations that much. Potential energy from falling is according to the equation Mass * height * g. If the mass is considered to be proportional to the volume that means height counts twice. The energy required to destroy a building should also be more or less proportional to its volume, so in tall buildings we should expect that the ratio of energy available from the fall to energy needed to destroy them will be favorable toward energy. Once the fall starts and gains some momentum, the materials should yield like butter.

The other arguments do impress me. Let me add some things from NIST's report on building 7.

http://www.nist.gov/customcf/get_pdf.cfm?pub_id=861610

Here's what NIST has to say:

NIST Report on WTC 7, executive summary wrote:WTC 7 was unlike the WTC towers in many respects. It was a more typical tall building in design of its structural system. It was not struck by an airplane. The fires in WTC 7 were quite different from those in the towers. Since WTC 7 was no doused with thousands of gallons of jet fuel, large areas of any floor were not ignited simultaneously. Instead, the fires in WTC 7 were similar to those that have occurred in several tall buildings where the automatic sprinklers did not function or were not present. These other buildings did not collapse, while WTC 7 succumbed to its fires.

Also:

NIST wrote:This is the final report of the National Institute of Standards and Technology (NIST) investigation into the collapse of WTC 7, conducted under the National Construction Safety Team Act. The report is the result of an extensive, state-of-the-art reconstruction of the events that affected WTC 7 and eventually led to its collapse. Numerous facts and data were obtained, then combined with validated computer modeling to produce an account that captures the key features of what actually occurred. However, the reader should keep in mind that the building and the records kept within it were destroyed, and the remains of all the WTC buildings were disposed of before congressional action and funding was available for this Investigation to begin. As a result, there are some facts that could not be discerned and, thus, there are uncertainties in this accounting. Nonetheless, NIST was able to gather sufficient evidence and documentation to conducts a full investigation upon which to reach firm findings and recommendations.

....
Factors contributing to the building failure were: thermal expansion occurring at temperatures hundreds of degrees below those typically considered in design practice for establishing structural fire resistance ratings, significant magnification of thermal expansion effects due to the long-span floors, which are common in office buildings in widespread use; connections that were designed to resist gravity loads, but not thermally induced lateral loads, and a structural system that was not designed to prevent fire-induced progressive collapse.

The report also mentions that the fuel lines that went to the backup generators were almost certainly not a serious contributing factor.

Within the building were emergency electric power generators, whose fuel supply lay in and under the building. However, the fuel oil fires did not play a role in the collapse of WTC 7. The worst-case scenario associated with fires being fed by the ruptured fuel lines (a) could not have been sustained long enough, or could not have generated sufficient heat, to raise the temperature of the critical interior column to the point of significant loss of strength or stiffness, or (b) would have produced large amounts of visible smoke that would have emanated from the exhaust louvers. No such smoke discharge was observed.

I like to focus on the reports of the fires themselves because those are the most possible to recreate with confidence, and NIST did take the trouble to set up experimental test fires to compare with their predictions. We can't know the specifics of what happened to the structural components with as much certainty, so that part of the story gets a bit hazy. Though I guess in WTC 7, they were able to narrow it down to a single support beam playing the crucial role.

I'm asking myself what's more parsimonious? A fairly low temperature fire displacing that beam by expanding nearby beams in a lateral direction...... or a nano-thermite device cutting straight through it? The answer depends on what you're already predisposed to believe about everything else, really.

I wouldn't place such an action outside the reach of Mossad. They've got a super-holy outlook about things, where nothing is ever really wrong if it serves the greater good of Israel. They've done enough awful things I wouldn't be surprised if they killed 3,000 Americans too. It's also possible for simply greedy people, or "Bilderberg Group" type folks who think they're on a mission to restructure the world. Those kinds of idealists are no different from Islamic idealists. Crazy, kill happy, self justifying, & certain that history will see things their way. What I do doubt is that the government did it.

I have certain thresholds on these matters, and when you see a comic from xkcd on a topic like this, I think it's time to re-examine the vigor with which you ascribe to a given mode of thought.


http://xkcd.com/966/

Tooltip hover over text from the image on the page wrote:The "controlled demolition" theory was concocted by the government to distract us. "9/11 was an inside job" was an inside job!

iNow wrote:I have certain thresholds on these matters, and when you see a comic from xkcd on a topic like this, I think it's time to re-examine the vigor with which you ascribe to a given mode of thought.

I don't really see what comic has to do with the science behind the collapse of the WTC towers, besides- as I keep saying, re-investigating the collapse of the WTC towers is most certainly not a bad thing, it's science through reliability and repeatability. But, of course, anyone who questions the official story is either a "paranoid conspiracy theorist", "an ignorant troll" or an "extremist"...

It's funny though, I was always under the impression that science is all about questioning and being sceptical (albeit, not too sceptical of course)...

First of all, I never suggested you were a troll, ignorant, extremist, or otherwise... and I don't think that's been a very common response in this thread or others. At other sites, I've seen that happen, but I think responses here (with perhaps one or two exceptions) have been quite productive. Maybe I'm wrong, it doesn't matter though.

Yes, good science is about questioning, showing skepticism, and falsification. It's also about accepting evidence which goes against what we want to believe.

Where things breakdown a bit, though, is when the evidence is rather clear and it gets ignored anyway in favor of some... okay, I'll go ahead and say it... extreme hypothesis.

the funny thing about engineering is that, under circumstances that appear to be identical, structures can behave in totally different ways - presumably through the interaction of multiple components, which can set off a different train of events depending on slightly different initial conditions
that's why engineers use safety factors in their calculations, and that's why scientific experiments may only give an indication of possible behaviour during structural collapse

marnixR wrote:the funny thing about engineering is that, under circumstances that appear to be identical, structures can behave in totally different ways - presumably through the interaction of multiple components, which can set off a different train of events depending on slightly different initial conditions
that's why engineers use safety factors in their calculations, and that's why scientific experiments may only give an indication of possible behaviour during structural collapse

Buckling and material failures are highly non-linear phenomena. Throw in the fact that structures have lots of unknowns --asymmetries, unknown load variations, joint strengths, geometric tolerances, defects, material variability, etc. -- and it is no surprise that the characteristics of a collapse are extremely variable.

Safety factors are intended to accomodate a wide range of uncertainties, which may or may not be realized in practice. Because of safety factors and uncertainty, calculations are usually reliable in predicting positive structural integrity, but usually significantly underestimate the loads required to initiate failure.

It is the stress/strain state immediately prior to failure, not the failure and subsequent structural response that is of interest in diagnosing the cause of a failure. Determining that state can be quite difficult, perhaps impossible, and involves sophisticated methods -- watching news films is not adequate. Evaluation of the events following the initiation of the event is of much less interest -- we know how gravity works.

DrRocket wrote:

marnixR wrote:the funny thing about engineering is that, under circumstances that appear to be identical, structures can behave in totally different ways - presumably through the interaction of multiple components, which can set off a different train of events depending on slightly different initial conditions
that's why engineers use safety factors in their calculations, and that's why scientific experiments may only give an indication of possible behaviour during structural collapse

Buckling and material failures are highly non-linear phenomena. Throw in the fact that structures have lots of unknowns --asymmetries, unknown load variations, joint strengths, geometric tolerances, defects, material variability, etc. -- and it is no surprise that the characteristics of a collapse are extremely variable.

Does that make it surprising, then, that the observable characteristics of all three collapses (WTC 1,2, & 7) would be so very similar? Or is a generally vertical collapse into the building's footprint expected as the most likely outcome?

If its random, then I would think that two consecutive repetitions of the same "die roll" would be stochastically interesting.

kojax wrote:Does that make it surprising, then, that the observable characteristics of all three collapses (WTC 1,2, & 7) would be so very similar?

IMO, No. The discussion taking place here reminds me of numerology... looking for patterns on the periphery where none are needed to fit the evidence.

iNow wrote:IMO, No. The discussion taking place here reminds me of numerology... looking for patterns on the periphery where none are needed to fit the evidence.

In some cases maybe not quite as rational as numerology.