Hello,
I agree with Gretavo here that we have reached something of an impasse.
I think a lot of interesting points have been made in the past few days,
and I've learnt a lot from trying to answer many of the questions that
have been raised. On the other hand, I think we seem to have exhausted the
topic of the physics of the collapse at least for now. So, I would like
to answer a few of the objections that were raised but then hopefully we
can move on, as Gretavo and Lex have been suggesting, to other topics
including
human issues of motive.

1)
The first question that has been raised is one of temperature. I think it
is generally agreed that the jet fuel burnt out soon after the crash ..
the crash itself caused major structural damage and ripped out the
insulation. The fire was then fed by fuel present locally.
The method they use to estimate the intensity of the fire is quite
interesting. There is a paper on this by a large team available at:

http://wtc.nist.gov/pubs/WTC_total__rept.pdf

They look at pictures of how high the smoke plume rose from the WTC
towers. Using this they can estimate how much heat was being generated by
the fires. It turns out that the fires were burning at about 1 GW/m^2.

I think this is the reason that NIST used a similar figure in their test
..this figure(of 900 MW/m^2, I think) is criticised on the wtc7 site, but
it comes from the calculation cited above.

I have limited access to computational facilities right now, and cant
access the NIST report but NIST also
noted the presence of people and their model generates a temperature
distribution in the building that does not involve ultra-high temperatures
near where people were observed.

2)
The second question has to do with the presence of heat at the
bottom of the ruins. Again, I think the heat of any kind of explosion
would have been
overwhelmed by the heat generated by the crash itself. Hitting a nail with
a small hammer makes the nail quite hot and some of the metal in the
basement of the WTC was probably mutiliated beyond recognition. I would
suspect that the metallurgical analyses cited in previous emails are done
on relatively undamaged pieces of metal that were not at the bottom of the
crash.
So, I'm not sure if this can be used as an argument for an explosion.

3)
I realise that building demolition is quite an art and that sometimes
buildings can be made to 'tip over' in demolition.

I think its easier to tip a building over by means of an explosion than by
means of a plane-crash. The reason, is that plane crash is a highly
'inelastic' process. In fact, in a calculation I did in a previous email
regarding the energy required for 'tipping over', the energy of the
plane-itself was I think several hundred times larger than the kinetic
energy that was imparted to the WTC.
An easy way to understand this is that if you throw a ball at a bottle
placed on a smooth floor the bottle tends to move backwards apart from
toppling. The WTC could not 'move' since it was held solid by its
foundation... this means most of the energy of the plane was wasted.

In an explosion, by contrast this is not true. If carried out properly,
all the energy of the explosion can be used to tip the building over.

Also the larger the building the harder it is to tip it over. For small
buildings, 10 stories, I think its quite an art to make the building
collapse in its 'footprints'. For the largest buildings in the world, like
the WTC, I think it would be hard to make them do otherwise.
---------------------------------

My personal biases are that I am a lot more willing to trust a consensus
amongst structural engineers than amongst intelligence agents. This is
why, I'm reluctant to dismiss the reports by NIST and the dozens of other
papers that have ben written on the subject.

I think we actually have some level of precise knowledge about buildings
and their design and its much harder to fake a report about the structural
engineering of the WTC(and much easier to catch such a fake) than a report
about Iraq having WMD.

Of course, I may be wrong here.. but those are my biases.

I think that there are many interesting questions that remain to be
discussed, in particular the extent of complicity of the Bush
administration in the WTC attacks. I agree with Lex that Bush, Cheney,
Rumsfeld are mass-murderers and vicious specimens of the human race. On
pragmatic grounds, I think they would have been scared of engineering an
attack of this kind .. a theory that I find more acceptable is that they
had foreknowledge and turned away. This discussion though, is also a
very interesting one and I'm sure many of us on the list will learn a
lot from it. this may be a fruitful alternative to the discussion on
the physical aspects of the collapse!

in solidarity,

Suvrat