Re: Physics of the 9/11 building collapses?

Edward Green wrote:

hetware wrote:
Well, now you're asking a hard (as in hard vs. soft) question, so "it
seems reasonable to me" is probably not an adequate answer. However:
dropping 20 to 30 floors of an office tower 20 meters (accepting your
figures) is a pretty large hammer, don't you think? It certainly
doesn't seem unreasonable.

But even if, for the sake of analysis, we /do/ accept the additional
assumption that the buildings would collapse under such conditions, there
are still many unanswered questions regarding the mechanism of collapse. I
have not seen any detailed engineering diagrams of the composition of the 1
and 2 WTC cores. I guess it's possible that the massive columns failed at
the splices, or something. The physical work required to cause such a
failure may not be significant in comparison to the amount of potential
energy of position stored above the points of failure. But this is all
very speculative without both design details and physical evidence.

The simple pancake model of one floor crushing the floor beneath it would
almost certainly have taken far more time than did the actual collapse.
I'm not sure how to estimate the work required to crush a floor, but simple
SWAGs lead to collapse times much higher than are calculated with a pancake
model assuming no structural resistance.

Hah. Now we uncover our deep seated prejudices. ;-) I happen to have
been born and raised in Manhattan, so it seems quite natural to me that
people should live stacked up like coral cells.

<offTopic>
I spent a couple weeks in NYC when I was about 11 years old. I distinctly
recall that I felt uncomfortable with the population density. But that is
off topic. And the topic of this thread is very important.
</offTopic>

Supposing this were true, I'm not sure it would be evidence on the side
of explosives. What would be the relative contribution of a sufficient
amount of explosives

"Explosives" is probably not the correct term to use. "Cutting charges" is
probably a better concept to explain the significant amount of heat
observed.

to do the job, vs. the graviational potential
energy and ordinary combustion?

Gravitational potential energy is worth considering, but my intuition tells
me it would be unlikely to cause the observed thermal patterns. It also
appears that what NASA and USGS observed was only superficial. There seems
to have been much more heat hidden under the rubble. Moreover, the heat
appears to have been concentrated in the steel. That is suggestive of
thermite.

Ah. But they go hand in hand, from my point of view. We are not
conducting a hard engineering review of all the available data, in
light of expert knowledge of structures.

What I am trying to do is to decouple the human factor from the physical
analysis. If the collapse of the buildings can be explained based on
reasonable assumptions regarding the initial conditions, then any
subsequent investigation into who was behind the collapses would take a far
different course.

We are having a discussion as
more or less informed laymen of the relative plausibility (appropriate
Bayesian prior) of various scenarios -- at least that's what I think we
are doing. Of course it is of the very nature of Bayesian priors that
they are subjective, but not therefore that their basis is outside the
realm of rational discussion. In particular, the assignment of our
best rational prior probability to one of two possible scenarios (say)
involves all our own prior knowledge, including our knowledge of human
behavior. Humans after all were part of the process, no matter what
happened.

Indeed. OTOH, the art of problem solving in physics has to do with
abstracting essential aspects of a problem and analysing them in isolation.
I do agree with Hofstadter's warning against being overly reductionistic,
but he also gives the opposite warning.

I was merely presenting an alternative third scenario to (1) bin Laden
orchestrated it all (2) the evil US government orchestrated it all: (3)
bin Laden orchestrated it mostly, with help from evil elements in the
US government. I wasindicating that, given my own prior experience,
that if you "want" to implicate the US government, I find (3) a vastly
more probable scenario than (1).

<offTopic>
Well, there are a lot of problems regarding the idea of a broad-based
conspiracy. There simply could not have been too many people aware of the
whole plan - no matter what that plan was, or who was doing the planning.
The idea that "the government" is behind it are nonsensical. I've been a
US DoD employee (Soldier). My father was employed by the US Government as
a safety engineer for 40 years. His second wife is currently employed by
the US Government. I would never, my father would never, and his wife
would never condone or wittingly participate in such a conpsiracy.

There appears to be good evidence that the video tapes where Osama bin Laden
supposedly takes credit for the attacks were fake. But that doesn't mean
the tapes originated in Doug Feith's Pentagon office. It's possible an, as
yet unidentified third party would have been the actual force behind the
attacks, and they played off of the US Government's interest in bin Laden
as a decoy.

There is also the notion of "unwitting accomplices" who, for whatever
reason, might avoid considering the possibility that high-level government
officials might have been behind the attacks, or at least complacent in not
thwarting them. There could be multiple motivations for covering up
different aspects of the whole picture. So could simply be CYA.
</offTopic>

I will admit you have me thinking, and while I still find revisionist
histories of class (2) to be in the same category as denial of WWII
genocide

<offTopic>
Again, this is off topic, but I will suggest you look into that matter a
bit. There are _many_ aspects of that history which have been quietly
revised in profound ways. If you have not watched the video on the first
link in my signature, your probably should. Also look into the case of
Walter Lüftl.
</offTopic>

or the Moon missions,

As for the moonshot, I believe German engineers really did put a man on the
Moon. There are very detailed and convincing explanations for how this was
done. People can repeat the math and physics to verify that the mission
was possible.

some of my gut feel that people in goverment would be _incapable_ of such
infamy do not stand up to closer examination.

<offTopic>
I have more doubts regarding the /competence/ of those who would have been
involved than I do regarding their moral integrity. But, bear in mind that
I am not promoting any "conspiracy theory". I am trying to assess the
existing evidence which intelligent people have identified as questionable.
</offTopic>

To wit, I note that the history of the twentieth century
is replete with governments which did delibrately murder vast numbers
of their own people, and, without really trying, I'm aware of at least
one case where it is widely accepted by mainstream history that an
"atrocity" was staged for manipulating public opinion (the Reichstag
fire).

<offTopic>
There is also the alleged staging of the Gleiwitz radio station attack. Of
course, the Nazis blamed the people who gave you the King David Hotel
bombing.
</offTopic>

Ok... since it is certainly well attested that humans in power can and
will act the way you seem to be hinting that a certain government close
to us may have acted here, I have to ask myself why I find it so
improbable? Are we a better class of people than those other bastards?
Probably not genetically -- we _are_ them, so to speak. However, for
all the flaws one can find, I think we have a better system of
government than was in place to facilitate all the governmental mass
killings one can think of -- mostly dictatorships.

<offTopic>
http://www.redstone.army.mil/history/airfield/chapter1.html
Hamburg, Dresden, Cologne, Essen, Freiburg, Dortmund, Berlin, Munich,
Tokyo...

http://www.armageddononline.net/image/nagasakibomb.jpg
http://www.gwu.edu/~nsarchiv/NSAEBB/NSAEBB162/hiroshima-1.jpg

And that's just a start.
</offTopic>

What is 'my scenario'?

That parties unknown rigged the towers with explosives?

The only part I am actually trying to evaluate in this newsgroup is the
physical plausibility that these three buildings were destroyed using
controlled demolition technology. Or perhaps, put a different way, how
plausible is it that they were _not_ destroyed through controlled
demolition?

I'm trying to explain the physical evidence, not who done it.

There is overwhelming evidence that aircraft were hijacked,

Are you speaking of hijacking the traditional sense of human beings either
controlling the pilot through physical threats, or replacing the pilot with
another human pilot? What evidence for this actually exists?

and in fact hit the towers.

The evidence for planes hitting the towers and the Pentagon is pretty solid.
I will admit, the Pentagon impact has some aspects which do raise a few
questions.

Conspiracies only remain secret if
there are a very small number of conpirators. Oliver North's dealings
and Nixon's activities _might_ have remained undetected -- though they
did not, and they only involved a small number of conspirators.

<offTopic>
I tend to agree, but what I have learned by studying the work of revisionist
historians has shown me that it is possible to generate illusions through a
kind of propaganda-fed mass hysteria. Regardless of what a person
concludes about the alleged existence of homicidal gaschambers at
Auschwitz, it is quite clear that there were many conclusions about what
happened that survived for the better part of a century before the record
was set right. http://www.jedwabne.net/
</offTopic>

If you want some unindicted co-conspirators -- which I still have a
feeling is your agenda, despite your claims to be considering only "the
physical evidence",

There are people who claim the events of 9/11/01 were extremely different
from what we have been told. These people are not stupid. I started
looking into the evidence, and much of what they've pointed to as
suspicious does indeed look suspicious. One very significant part of their
criticism of the official account is that three huge buildings collapsed on
the same day in a way that appears suspiciously similar to what one would
expect in a controlled demolition. To my way of thinking, the building
collapses are the most tangible items available for objective analysis.

the highest probabilities scenarios would involve
only a minimal number: say, some rogue elements in the CIA who were
secretly helping bin Laden, providing him with intelligence, or finding
ways to quash or misdirect investigation which might have foiled his
plot: that's a conspiracy theory with legs.

<offTopic>
I've long suspected that to be the case.
</offTopic>

Forget about controlled demolition: I'm sorry, but that's just nuts.

What about the idea that these buildings were rigged to selfdestruct in the
event of a catastrophic structural compromise, but this built-in 'building
suicide' feature was unadvertised for obvious reasons?

--
http://www.vho.org/GB/c/DC/gcgvcole.html
http://www.vho.org/GB/Books/dth/
http://www.germarrudolf.com/
http://www.ice.gov/graphics/news/newsreleases/articles/051115chicago.htm
.

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