Before delving into details of existing evidence, I will point out two problems I have with your approach, Suvrat.  Your method thus far seems two-pronged: 1) citing the conventionally accepted technical studies which make claims that can only be evaluated by experts, and 2) lots of physics equations.

On top of that, you seem in rather a rush to have us move on.  So first I ask you to slow down a bit and give us time to respond (though I'm sure we can catch up while you try to debunk the demolition of WTC7, or explain why the demolition has never been admitted beyond Silverstein's taped remarks that apparently never aired on TV)

Second, I would encourage you to make an effort to treat this not as a case study in physics.  While certain elucidation is possible with equations, using them as liberally as you do leads to some confusion, and not from people not understanding the equations themselves.  The arguments about angular momentum and the "tipping"  as opposed to symmetrical fall of the towers I think are misleading.  A simple thought experiment should suffice.  Assuming a solid structure being struck by a projectile is one thing--your center of gravity argument is valid there.  But no one to my knowledge has suggested that the towers should have tipped over from the impact of the planes.  The problem we have is that since the damage at the impact sites was not equal across the entire range of the structure, it seems remarkable that the top sections above the damage would fall straight down.  Pictures of one of the towers show conclusively that the top section indeed did not fall straight down, but is tipping to one side, which seems to indicate that one side (presumably the side damaged by the plane, did indeed begin to fall first.  As massive as this piece was, I don't think we can immediately assume that the weight of its falling would have caused the completely undamaged and much longer lower section to simply fall straight down under the weight of that collapse.  Why didn't that section, once broken and falling, encounter any resistance that we know could well have changed its trajectory from straight down?  If the piece was heavier and denser than the bottom section could support, or if the bottom section had been weakened, we could see the straight down falling.  But since this section was relatively small compared to the rest of the (undamaged?) structure, I don't see why it's so hard to imagine that it could have just broken, and yes, toppled off the top of the building.  Otherwise why would there be any science whatsoever to bringing down buildings?  If they always fall straight down regardless of the nature of the structural failure affecting them?

More later!

joustingly yours,

gretavo

Suvrat Raju wrote:

1)
An addition about the towers collapsing in their 'footprints'. Actually,
this is not at all remarkable. For an object to 'topple over', its center
of gravity needs to move beyond the base of the object. For a huge tower
weighing thousands of tonnes, a hurtling aircraft does not provide even
a fraction of the angular momentum required for this.
in an explosion or collapse or anything, fragments can fly far but the
bulk of the building just HAS to come down in its footprints.

details of a calculation demonstrating this are in the postscript of this
email. The result, though is that plane had about 1/10,000 times of the
requisite energy required to tip the building!
So, the building HAD to fall in its footprints.

2)Also, the claim that the building was designed to withstand an impact of
a boeing 707 comes from a single source which is a document produced by
the Port Authority, typically used for "talking points". There is no
credible substantiation of this claim. Nor is there any evidence that any
investigation of the actual effects of a 707 crash was carried out.

Suvrat
P.S: Details of Calculation

Let us do this for the case  of the two towers. The towers were about 1400
ft~400 m tall and 210 ft~70 m on the base. They would have to tilt by about 8 degrees to tip over.
gain in height of center of mass = 200 m * cos(8) = 200*.01 = 2 m.
[taking a weight of half a million tonnes]gain in potential energy = m g h
= 5*10^8 * 10 * 2 = 10^10 joules.

this energy must come from the initial rotational energy the plane
imparted to the building. This is NOT the initial kinetic energy of the
plane. We can calculate this rotational energy from conservation of
angular momentum. Lets assume the plane hit the top of the building.
Then
p_{plane} * L = I w = M L^2 w/3

[assuming a building height of 400 m, a plane mass of 200 tonnes, plane
speed of 360 km/hr, a building mass of half million tonnes, we find]

w = 3*10^(-4) rad/s.

What is the ratio of this initial rotational energy to the energy required
to tip the building:
(1/2)I w^2 = 1.2*10^6 J

ratio ~ 10^(-4)


On Fri, 9 Dec 2005, Merrick Lex Berman wrote:

 

a few added items on physics:

seismic spikes:
many articles generally debunk the idea that seismic spikes were caused
by explosives at the base of the towers before the mass of the buildings
struck the ground.   nonetheless i remain slightly skeptical that the
largest spike would occur at the onset of the collapse if the pancake
theory is true.  also it seems odd to me that the towers collapsed
directly onto their own footprints.   i have seen implosions and even
under IDEAL circumstances a lot of things could go wrong.   when a
single plane crashes at a lateral angle into one corner of a structure
like the WTC (which was DESIGNED to absorb a plane impact) i am
skeptical that it would cause such a perfect collapse.  that just
doesn't make sense to me either statistically or mechanically.  the
mechanics would argue that the WEAKENED point would cause a lateral fall.

hot spots:
okay, tell me why molten pools of metal remained too hot to approach and
were visible in space for weeks after the collapse?   and why did the
metal show these characteristics:
*Rapid oxidation and intragranular melting of steel pieces*
The limited metallurgical examination of some of the few pieces of
structural steel that escaped the blast furnaces shows very peculiar
features, such as rapid oxidation turning inch-thick steel into
paper-thin scrolled pieces, cavitation giving steel the appearance of
Swiss cheese, and intragranular melting. These suggest a more exotic
process of destruction than mere explosives.

how did this occur?  you tell me!  and furthermore, why was the metal
IMMEDIATELY hauled away and disposed of, instead of being meticulously
examined?  that in itself is beyond strange... it simply stinks.

building 7:
it did not have significant damage or fire and went straight down.
you've got to be kidding me if you think it was not imploded.  there is
no mechanical stress that has been mentioned (to my knowledge) that
offers even a remotely plausible explanation of the physical collapse of
wtc7.   therefore, one may right question, in my view, the causes of wtc
1 and 2 collapses as well.

lex



Suvrat Raju wrote:

  

To conclude I find the evidence for the "controlled explosion hypothesis"
scanty at the moment.