Hello all,
I want to reply briefly to the points that have been raised.

1)the NIST report is not the only report on the issue. The page:
http://www.icivilengineer.com/News/WTC/report.php

links to many technical reports on the collapse. I cited the NIST report,
because it seemed to be most comprehensive.

In addition, Silverstein commissioned his own report. This was performed
by Weidlinger and Associates. So, did the insurers. Their report was done
by 'Failure Analysis' and may be found online at:
http://reconstructionreport.org/article.pl?sid=02/11/01/1916239

The insurers, note, had a lot to gain from the controlled demolition
hypothesis but their comments on the weidlinger report have to do with
details.

A series of MIT professors also wrote articles on the subject that may be
found through the first link above.

2)The question of why the towers fell straight down and whether the force
of the upper floors collapsing was enough to cause them to fall is
addressed in the paper by Bazant and Zhou(Journal of Engineering Mechanics
2002). It may be found online at:
http://www-math.mit.edu/~bazant/WTC/WTC-asce.pdf

Briefly, the paper concludes, based on simple assumptions, that the force
of the upper floors collapsing was about 31 times larger than the load
the structure was designed to hold. This is an approximate number and
probably will be largely corrected because the lower structure probably
had large amounts of surplus strength but this is still quite a large
number.

3)The criticisms made on the wtc7 website are somewhat unconvincing. For
example, the person says that NIST seems to have ignored 'conduction'
between different elements. This seems incorrect. What NIST says is that
it modelled individual elements of steel as 'finite-elements'. These
elements interact with each-other and transfer heat. In fact, one of the
points of the experiments on small elements of steel was to determine the
heat-conductivity.

Also, while the NIST report may not be trusted, given all the effort they
put into thermal modeling, this allegation that they made the most
elementary schoolboy mistake is somewhat strange and off the mark.

Finally, the claim that the steel-structure would take the 'heat away'
does not seem convincing. In fact, the lower portions of the tower had
their insulation intact. Under these conditions a temperature gradient
would have formed with the damaged and burning tower at significantly
higher temperatures than the section below. This is not inconsistent with
the 'conduction' of heat.

4) Also, people wanted NIST to generate a 'visualization'. Generating an
accurate visualization is actually quite a hard task requiring a lot of
computing effort. In fact, one of the major achievements of the simulation
done on the Pentagon, by people from Purdue University was they were able
to 'visualize' the sequence of events. It is reasonable for NIST not to
engage in this effort unless there was strong motivation.[for the purdue
university people, they wanted to show their supercomputing prowess].

5)Also, it makes sense that NIST stopped their simulation after
'initiation' of collapse. Their entire analysis was done in a static mode,
with things sitting in their places and getting heated and weakened. The
collapse, itself is a different ball-game and much harder to simulate
accurately. All, they need to show is that collapse was initiated, and the
paper referenced above seems to make that clear.

 5)Finally, there is again the question of an alternate theory. With any
study as complicated as this, it is always possible to point out
omissions. The issue of a convincing and worked out alternate theory
remains. The controlled explosions camp been able to garner some
structural engineers to perform a study and calculate the amount of
explosives and show that this theory fits the observed data better.

Suvrat



On Sat, 10 Dec 2005, gretavo wrote:

OK so I skimmed the 298 pages of very accessible writing in the NIST
report.  The dedication on page 13 of the PDF (which is locked and can't
be copied from, hmm) is the first problem.  You have to read it to get
the whole idea, but it begins the report by stating that "jet-laden
planes were flown into the towers by terrorists"  a claim for which
there is as yet no evidence.  In addition, the report was prepared by
NIST, a section of the department of commerce, which is part of the
executive branch and not at all unbiased.  It must in our investigation
then be treated as a questionable source.  This is especially troubling
given the complexity of their analysis, including the computer modeling
which naturally could have been designed, through trial and error, to
simulate as closely as possible the results of the disaster without
necessarily bearing close resemblance to what actually occured.  The
length of the document suggests exhaustiveness, but we know from the
alternative explanation sites that there are some inconsistencies if you
bother to look for them--pictures, for example, showing people trapped
in the towers, poking their heads out of the damaged areas, weakening
the supposition that intense heat was responsible for the structural
failure.  But again, we are just beginning this particular discussion,
and the NIST report is just one report with dubious provenance, imho.

gretavo

Suvrat Raju wrote:

Hello David, Gretavo and all:

Again, I would like to encourage everyone to have a look at the NIST
report I linked to in the last study. It supersedes other studies and
articles written on the subject. One of the reasons its hard to discuss
WTC 7 or the Pentagon with the same certainty is because no comparable
reports exist for these sites. The WTC 7 NIST report is still in
preparation and no comparable study is planned for the Pentagon.

1)In particular, I think the report would answer many of the questions that
David asks below. For example, the fires did not go out but kept burning.
Using visual evidence, the report is able to reconstruct temperature
contours in parts of the building.
also, one of the more impressive parts of the report is the very detailed
computer simulation they did. It seems to reproduce, with some fairly
impressive accuracy, much of the observed data. This can also be used to
reconstruct temperature contours.

The simulation and visual data also help track the progress of the
weakening of structures. In the simulation, collapse was initiated after
-- I think 102 minutes -- which is within the actual collapse time to
within a few minutes. Once collapse was initiated, by the top 15 floors
falling down, the rest of the building collapsed immediately.
The report does not deal with the collapse, but the point is that it would
be unreasonable to think that collapse occured in a 'pancake' fashion. The
onset of collapse at the top could have caused the steel to buckle
along the length of the building.

2)
About WTC 7, the only report so far is the FEMA report that is not nearly
as good as the NIST report. It may be found at:
www.fema.gov/pdf/library/fema403_ch5.pdf

However, they do make the point that waste from WTC 7, found 11,000
gallons of diesel fuel. WTC 7 stored tens of thousands of gallons of fuel
within the building to supply emergency generators for the New York
Emergency Management Service, Silverstein and Associates and the US secret
service. This is what is said to have caused the collapse. The FEMA
report, though, does have several photographs of WTC 7 that show it to be
highly damaged after a fire that burnt for many hours.

Also, NIST did make some preliminary statements to the effect that debris

>from the collapsing towers had affected WTC 7 to a greater extent than

previously supposed. Again, speculation on this must await release of the
final report by NIST.

3)About the cover-up, it is correct that much of waste was carted away but
as I mentioned in my earlier email to Lex, NIST was able to examine
several samples of steel from the two towers. So, it is not true that all
evidence was disposed of. It is true that the government was VERY careless
with preserving evidence.

4)About 'molten steel', again see the report on the initial analysis of
steel from WTC 7.
http://www.tms.org/pubs/journals/JOM/0112/Biederman/Biederman-0112.html
It points out, that the heating of the steel lead to the oxidation of
steel. The presence of sulphur led to the formation of an 'eutectic
mixture' of iron-oxide and iron-sulphide. This melts at temperature far
lower than steel.
This is the molten metal that observers seem to have referred to.

5)In all this, it seems that two points cannot be covered .. one has to do
with why the collapse wasnt 'messier'. As I mentioned, there is a limit to
how messy it could have been even under very general considerations but
you are correct that this does not exclude messiness. This, it seems to
me, is a minor criticism and should be put to a structural engineer who
should be able to clear it up.
The second has to do with the squibs and the claim that this was caused by
falling debris. Again, I think it would be incorrect to take the pancake
theory at face-value. Minor collapse, of some kind, was probably initiated
simultaenously across the length of the building. This was then completed
by 'pancaking'. This would explain the lack of resistance to the visible
free-fall collapse of the top of the building as well as the squibs
appearing low-down in the collapse.
I admit this is not a rock-solid theory, but again this criticism is not
devastating.

----------------
I apologise for the excess of equations in the previous few emails. Not
much more remains to be said in that direction. I also think, that it is
important for the opponents of the conventional theory to propose at least
some alternative and defend it. It is certain that with a day or so
of research, I will be unable to answer many questions regarding the
details of the collapse[such as the squibs], but this in itself does not
prove much. As of now, it seems the conventional theory seems to have
much more ammunition than alternatives.

in solidarity,

Suvrat







On Sat, 10 Dec 2005, David Mericle wrote:

Hi all,
I'm glad we are having this debate, especially with several physicists in
our group.  I second the request by Gretavo that we not move on too quickly.
I'm glad we're discussing this piece-by-piece, as there are many questions
and pieces of evidence that need to be carefully examined.  I read the NOVA
interview and the paper by the BYU physicist and a few other things sent
out, and found them all interesting.  Below is my response to what has been
said so far about the collapse; sorry if I repeat Gretavo in places.


General criticisms:

1.  The argument that the building had to fall down, rather than to the
side, seems to me to present a false dilemma characteristic of Eager's
general perspective.  That is, it takes for granted that the official story
is basically correct, that the planes somehow caused the building to fall.
It then seeks the most probable explanation given these assumptions.

To conclude that it is incomparably more likely that the building would fall
down rather than to the side is not the same as saying that it is at all
likely that the building should, under these circumstances, have fallen in
the first place.  In general, I feel that, as the BYU physicist suggests,
Eager and others have been contrasting the likelihood of explanations that
assume the official story, without ever commenting on how likely their
favored explanation actually is.

2.  The cover-up seems to me to be one of the strongest pieces of evidence
that the official story is false.  In the particular case of the WTC
collapse, there seems to have been a major cover-up involving immediately
removing the steel and evidence at the base in very strange ways.

3.  The point Lex makes is important: If you can't explain WTC7, then you
have to be more open to unnatural causes of the collapse of WTC 1 and 2.  In
other words, you might think that the probability of unnatural collapse of
WTC 1 and 2 is low, but that the probability of unnatural collapse of WTC 1
and 2 given a controlled demolition of WTC 7 is considerably higher.


Specific criticisms of the collapse account:

4.  I still have trouble with the fact that the twin towers fell straight
down.  It seems to me that that the point is not that the entire tower
should have fallen to the side, but rather that the fall should have been
much messier than it was.  For example, if one side of a floor broke faster
than the other side, wouldn't the above floors slide off to the side?
Wouldn't we expect this to happen quite a bit in the course of the fall?  I
don't have a sense of how messy the collapse was, but it seems a little too
clean and perfect.

5.  Why the long delay before the towers collapsed?  It seems implausible
that the time when the heat caused the building to collapse would be so long
after the initial crash.  Fuel would burn up quickly, and the black smoke
seems to indicate the fire had nearly died.

6.  As far-fetched as it sounds to talk about controlled demolitions, when I
watch the videos, especially of WTC 7 collapsing, I just cannot get the idea
out of my head.  WTC7 didn't even look damaged, and yet it just collapses
straight down.

7.  The speed of collapse still bothers me in two ways.  First, it doesn't
make sense that the buildings would stand for over an hour and a half, and
then collapse uniformly and instantaneously.  I can't believe that the
critical amount of heat needed would be reached everywhere suddenly and
simultaneously.

8.  Second, it doesn't make sense that the buildings collapsed to the ground
so fast.  On this second point, Suvrat's argument about the pressure waves
passing through is interesting, but I still think that cannot explain the
total lack of resistance from each floor and the consequent speed of the
fall.  Also, I'm certainly not a physicist, but I don't understand how we
get from pressure waves to the steel totally giving way or breaking or
whatever they claim happened.  In fact, it seems to me that with regard to
explaining the collapse, this is a weaker argument than the claim that the
steel was weakened by heat from jet fuel (not that I believe the jet fuel
was there; what I mean is that I understand how the steel being weakened
contributes to the collapse, but not how the pressure waves contribute).

9.  I don't buy the explanation of the squibs.  In the BYU professor's photo
at
http://www.physics.byu.edu/research/energy/9-11%20Picture7%20(squib1).jpg,
the squibs occur too far down from the part of the building that has been
destroyed.  There are too many intact floors between the part destroyed and
the squibs.  That said, in the videos of WTC7, I can't really see the
squibs, and in the picture, the squibs don't seem particularly systematic,
so I'm not sure how well they fit a controlled demolition story.

10.  Could the temperature really have been as hot as Eager says for a
prolonged period of time?  Are claims about this high temperature consistent
with other visual evidence from that day?

11.  Furthermore, his heat/temperature distinction seems to me to work
against, rather than for, the official story.  The claim that the
temperature got up to 1300F, itself open to doubt, is not enough; we need
the stronger claim that it remained at or above this temperature long enough
to raise the temperature of steel to a very high level.

12.  How do Eager and others explain the molten steel at the base?

If we eventually decide that there are serious unanswered questions that
remain outstanding, perhaps we could invite Thomas Eager to come talk to us?

David