In trying to come to terms with what actually happened during the collapse
of
the World Trade Towers, the biggest and most obvious problem that I see is
the
source of the enormous amount of very fine dust that we see generated during
the
collapse. Even early on, when the top of the building has barely started to
fall, we see this characteristic fine dust (mixed with larger chunks of
debris)
being shot out very energetically from the building. During the first few
seconds of a gravitational fall nothing is moving very fast. Where does the
energy come from to turn all this reinforced concrete into dust? It is
difficult to know the exact amount of energy it would take to reduce a four
inch
thick by almost one acre slab of concrete to a fine powder, but it is
clearly
very large. The chemical bonds holding the concrete together are very
strong, I
would guess several orders of magnitude greater than the gravitational
energy of
a floor falling through one or several stories. And yet the collapse occurs
in
about 9 seconds, only slightly more than an unresisted free fall from the
same
height, indicating that there was very little resistance.

The floors themselves are quite robust. Each one is 39" thick; the top 4" is
a
poured concrete slab, with interlocking vertical steel trusses underneath.
This
steel would absorb a lot of kinetic energy by crumpling as one floor fell
onto
another. And yet we see a very fine dust being blown very energetically out
to
the sides as if the entire mass of concrete (about 400,000 cubic yards for
the
whole building) were being converted to dust.


Puzzling Evidence: the Videos

The video "--=Ground level closeup of WTC South Tower collapse and escape
from
dust cloud.avi" shows the WTC south tower very soon after it starts to
collapse,
and shot from almost underneath the building. (You can see a lot more if you
can
slow it to .25X or go frame-by-frame.) At the very start of the clip you can
see
how perfectly even the collapse is, advancing with what look for all the
world
like rows of explosions progressing in a perfectly straight line around the
two
sides of the building that you can see, and advancing down in an extremely
uniform way. As the demolition wave advances there is only dust and smoke
where
the top of the building used to be, and a great quantity of dust mixed with
small pieces of structural steel is ejected out horizontally and quite
rapidly.
To account for this very rapid ejection of debris without the use of high
explosives, especially in the early stages of the collapse, seems quite
impossible.


If you look closely as the wave travels down it seems to spare the corners,
perhaps letting them lag behind to help keep the implosion aligned. The
demolition wave is clearly advancing ahead of the actual collapse of the
structure, and speeds up as it travels down. The delays between demolition
charges would have to be very precisely controlled to create this effect,
suggesting to me that each floor was wired to a separate detonator, with
control
of the sequencing most likely done remotely. This would also allow the
collapse
to be triggered from the point of impact of the plane to make it look more
realistic. Such sequencing could easily be done from a laptop connected
wirelessly to the towers, as long as each floor could be detonated
separately.**



Soon the photographer is running away to escape the dust cloud, holding the
video camera at his side and pointing back. As he runs you can see an
enormous
cloud of dust chasing people down several blocks of the surrounding streets.
The
cameraman and the people with him are running full tilt to get away from the
dust flow, which seems to rapidly fill all the streets for a several block
radius around the site. ("Close-up views of huge dust cloud from 1st
collapse.mpg" also shows an interesting view of the immense pillar of dust
where
the South Tower had been as it pours down and races out along the
surrounding
streets.)


The other striking thing visible at the beginning of the clip is how much
very
fine concrete dust is ejected from the top of the building very early in the
collapse. Since it should at most be accelerating under gravity at 32 ft.
per
second per second, things would actually be moving quite slowly at first,
reaching about 200 mph at the end of the ~1400' fall if nothing slowed it
down. It is very hard to imagine a physical mechanism to generate that much
dust with concrete slabs bumping into each other at 20 or 30 mph. And the
extreme fineness - I have heard it described as like talc - and uniformity
of
the dust makes its origin quite puzzling.


This huge amount of very fine dust seems to virtually fall in place, much of
it
within the outlines of the former building. This created a pyroclastic flow,
or
perhaps more properly a turbidity current: a slurry of dust and air much
denser
than the air around it, that can accelerate to considerable speeds as it
falls.
This is the dense cloud that chases the cameraman down the street for
several
blocks, and can be seen in several of the videos. From what I understand the
surrounding area for several blocks radius was covered by several inches of
very
fine concrete dust, which would seem to account for most of the concrete in
the
structure. And there seem to have been very few macroscopic chunks of
concrete
found at the sites, much less the pile of broken but not pulverized floors
that
one might reasonably expect to find after the dust cleared.


The Afterglow


This is perhaps the strangest feature of the collapse: in both collapses,
the
videos show a bright glow that develops as the bulk of the dust cloud hits
the
ground. A good example of this is "Close and medium view north tower-
immense
dust cloud and strange afterglow.mpg". At 45 sec., as the dust cloud from
the
North Tower collapse hits the ground, there is a sudden very bright glow
that
develops. It may seem at first that this is some kind of video artifact, but
a
similar glow is seen in several views, and occurs at the same point in the
collapses (see "Both collapses - bright afterglow at 1min 07sec.mpg"). At
about
16 sec. Into "South tower of WTC collapse from north, then closeup.mpg" we
see
the beginning of this glow after the South Tower collapse, but the clip
abruptly
cuts away before it is well established.

"Bright afterglow of south tower collapse.avi" starts after the South Tower
has
fallen, but a very bright and persistent glow can be seen where it had been.
The beginning of "Both collapses - bright afterglow at 1min 07sec.mpg" shows
the
South Tower afterglow, and the sudden "ignition" of the North Tower
afterglow at
1 min. 07 sec., which is so bright that it almost burns out the image.

I have no explanation to offer for this effect, and have heard no accounts
of it
being seen by witnesses. Is this something that shows up on video (near UV?)
but is not visible to the naked eye? All I can say is that it seems to be
real,
and occurs with both collapses.



** Actually the sequence of the south tower collapse is a bit strange. (See
the
video clip "--=Close-up of south tower collapse.mpg") First we see the top
of
the building start to tip to one side as a monolithic block, which we would
expect to continue to rotate and topple to the side. Instead, almost as soon
as
it starts to tip, the building below it starts to collapse, allowing it to
drop
straight down. There are very visible rings of explosions that start at the
level where the building has begun to tip and travel rapidly down the
building.
And instead of continuing to topple to the side, the top portion actually
telescopes into itself at the same time that it sinks effortlessly into the
building beneath it. Before it disappears into an immense dust cloud, we see
the distance between the roof and the bottom of the upper section actually
collapse to less than half its original height. This is especially
remarkable
because it is essentially in free fall at this point, so there should not be
any
internal forces causing it to collapse on itself.

On Sun, 09 Nov 2003 14:35:22 GMT, "STFU" wrote:

In trying to come to terms with what actually happened during the collapse
of
the World Trade Towers, the biggest and most obvious problem that I see is
the
source of the enormous amount of very fine dust that we see generated during
the
collapse. Even early on, when the top of the building has barely started to
fall, we see this characteristic fine dust (mixed with larger chunks of
debris)
being shot out very energetically from the building. During the first few
seconds of a gravitational fall nothing is moving very fast. Where does the
[about 500 lines of bull**** snipped]

WTF does this have to do with boatin? You need to get yourself to your boat,
ASAP.

John
On the 'Poco Loco' out of Deale, MD

Go to sciam.com and read "why the towers fell".

Please leave this newsgroup and find another to troll.