Acceleration + Serendipity

Some time ago I did an analysis of the downward
acceleration of the roofline of WTC1, the North Tower of the World Trade Center. I was only able to track the motion
through the first few seconds while the roofline was visible
above the debris cloud. I found that the drop of the roofline occurred with sudden onset and underwent a uniform
acceleration 64% of the acceleration of gravity. I started the current project to explore whether
the same acceleration continued all the way down, or whether it changed as the destruction
moved down the building.

I found the answer to THAT question,
but along the way I noticed something else
that is perhaps even more intriguing. We'll come to that unexpected
observation at the end of this video. One of the most conspicuous features of the
destruction of the Twin Towers on 9/11, 2001, was the rapid rate of fall. For most people, their intuition tells them
that buildings do not fall in on themselves, especially that fast,
in any kind of natural event.

Intuition does not have
the last word in a situation like this, but blindly accepting the contrary pronouncements
of authority figures is little better, and perhaps worse, as a guide to the truth. We need to look for ourselves. It is commonplace to hear that
the Twin Towers fell at freefall speed. As a point of clarification, the rate of fall
is characterized by acceleration, not speed.

This is more than just a vocabulary question. It involves a basic concept,
so let's pause for a little demonstration. One tool I use for studying motion
on video clips is a program called Tracker. It's part of the Open Source Physics project
and it's freely available on the internet.

What I'm going to do here is drop
a soccer ball and record its motion. To do that I have to add marks on each frame. The program collects the positions from the pixel
locations and the times from the frame numbers. It displays the data in a table and a graph.

This graph shows
the vertical position, y, vs time, t. What results is a picture of the motion
of the ball spread out over time. To translate the pixel positions
to actual measurements, I have to calibrate the image
by marking something of known length. In this video I'm holding a meter stick,
so by marking the ends of the meter stick the program can figure out how many pixels
on the video make up one meter in the real world.

Another thing we can do is
to look at other quantities. For instance if we plot the vertical
component of the velocity vs time we get a graph that looks like this. Note that the position vs time graph for free fall is in the shape of a parabola, and the velocity vs time graph is a straight line. What's going on here is that when I let go
of the ball the velocity starts out at zero and increases downward by equal amounts
in equal increments of time.

That produces a linear graph. Freefall would be a smoking
gun for explosive demolition because it would indicate zero resistance. Building 7 fell in actual
freefall for over 2 seconds. NIST has grudgingly acknowledged
this in their final report but has refused to even
address the obvious implications.

In my earlier video I measured
the rate of fall of the roofline of WTC1 for the first few seconds while it was visible and found that it came down
with constant acceleration, 64% of the acceleration of gravity. In that video I showed the fact that
the top section of the building accelerated, right through its collision
with the lower section, is also a smoking gun for explosive demolition. Watch the video
"Downward Acceleration of the North Tower." I won't repeat the argument here. In that video I noted that if
that rate of acceleration persisted the tower would fall in 11.5 Seconds.

Jim Hoffman, on his website
911research.Wtc7.Net, does a thorough analysis, from several lines of evidence, and concludes
that the total time for the North Tower to fall was approximately 15-16 seconds. I wanted to understand the rate
of fall beyond the first few seconds. Measuring the motion of falling
clouds of debris is difficult, so rather than a direct measurement I wrote
a program to put two sets of markers on a video of the falling tower. Both start at the height of the roofline.

The blue mark descends at freefall. The red mark descends at 64% of freefall. As we run through the clip, it is clear that the top of the debris cloud
does indeed lag behind both marks. Even the heavy falling debris near
the bottom falls at less than freefall because it is meeting air resistance.

So much for the original purpose of this project. However, along the way I noticed something else. One feature is actually
keeping up with the red mark, the original downward
acceleration of the roofline: that's the sequence of ejections at the
lower right, on the West wall of the tower. That means [that] this wave of ejections is the
fastest moving feature in the building's descent.

If anyone still believes these are
naturally occurring puffs of air
caused by some internal process, such as collapsing floors, they would need to explain how such a process
could propagate so fast within the building, nearly keeping pace with the heaviest debris
falling only through air just a few feet away. If one assumes the floors collapsed
to blow out this much material
in the leading wave of ejections, one would also have to explain how air pressure could be built up and maintained
higher in the building for the other waves of ejections that follow. The fact is, strong, focused ejections
are occurring on multiple floors simultaneously. The theory that these are simply
air being squeezed out defies both common sense
and any kind of honest analysis.

The most reasonable way to account
for the rapid wave of ejections is to recognize them
to be a timed sequence of explosions designed to destroy the underlying
structure of the building, top to bottom. Such a sequence would not be limited
by physical conditions in the building. The downward motion of the explosions is merely
a pattern designed purely for appearances, to mimic a natural collapse, and to stay
hidden under the canopy of the falling debris. If this was the intent, it was not
accomplished successfully as we can see.

Perhaps the reason the leading wave
of explosions propagates down the building at the same rate as the initial
acceleration of the roof line is [that] they were timed
that way on the assumption that the building would continue
to fall at the initial rate all the way down. That last point is just a speculation,
of course, but the measured outcome is not..