The Twin Towers

This page deals with evidence relating to both the North Tower (WTC 1) and the South Tower (WTC 2).

South tower, early in collapse

South tower, early in collapse

A frequent argument against the explosive demolition theory, as applied to the collapses of the Twin Towers, is that they do not look like conventional controlled demolitions, being carried out from the top down. This is true – normal demolitions are carried out from the bottom up. This argument carries no weight, however, as there is no reason why a demolition must be done that way. It is, after all, only a question of where the explosives are laid and the order in which they are detonated.

Bottom-up demolition is preferred, where possible, because much less explosive is required, as the mass of the falling building provides energy which assists the demolition. Obviously the towers had to be brought down from the top to create the illusion that it was caused by plane damage and fire.

There is however another interesting point. These towers were about three times the height of any building which had ever been demolished in the past. They were also very slender. Any attempt to drop them from the bottom would have run an extremely high risk that they would not fall straight down but would topple over. This would have had a devastating effect on the neighboring real estate and would have caused many more deaths.

One has to ask why bin Laden or al Qaeda would have worried about New York real estate and death rates. It is reasonable to believe that external terrorists would have had three concerns:

  1. To minimize risk of detection.
  2. To minimize cost.
  3. To maximize damage.

These concerns would have been best dealt with by using a small amount of explosive on one side of the towers, near the ground, so as to deliberately topple them, as one chops down a tree. Above all, the terrorists would have wanted to avoid detection. Imagine how difficult it would be for an outsider to install explosives all the way up these well secured buildings without detection. In contrast we note that it might not have been a very difficult task for an insider, as Marvin Bush, brother of George Bush, had earlier been a director of Securacom, the company in charge of security.

North tower, early in collapse.

North tower, early in collapse.

There are many lines of evidence for controlled demolition of the towers using explosives. The most glaringly obvious is the quantity of material thrown out from the towers as they fall and the violence of the ejection. Heavier objects lead the way and drag dust behind them in a curved path. The rate the dust falls is an indication of its density as will be discussed later.

The simplest hard scientific evidence for the use of explosives is found in the study of the rate of collapse. It is not quite as simple as in the case of WTC 7, where the average rate of collapse was so close to free fall that it is immediately clear that the only possible explanation is controlled demolition. In the case of the towers the collapse rate is slower so it is necessary to see whether any process other than controlled demolition is feasible.

An examination of the forces exerted in the collapsing building provides the answer. When a force is exerted on an object which is free to move, it will accelerate. Our everyday experience teaches us that the rate of acceleration is proportional to the force applied. It follows that if we can measure the acceleration we can calculate the force.

It is our knowledge of the rate of acceleration of a freely falling body that has enabled us to calculate the force of gravity here on earth. The rate of acceleration is found to be very close to 9.8 metres (or 32.2 feet) per second per second. If a body is falling at a rate less than that, there must be something applying an upward force, resisting gravity. We can calculate the size of the upward force from the reduction in acceleration.

This has been set out very clearly by David Chandler. He is a high school teacher and has the knack of explaining serious physical concepts in a very efficient manner. He shows that the acceleration of the roof of WTC 1 is constant right from the start and is 64% of the acceleration due to gravity. This means that the upward force restraining the fall must be 36% of the force due to gravity.

Now comes the essential clue to this debate. According to Newton’s third law, for every force there must be an equal and opposite force. This means that the falling top of the building must be exerting a force on the lower portion of exactly the same size, 36% of the force due to gravity, or 36% of its weight.

The building was designed with a substantial safety margin. At any point in its height, it was capable of supporting several times the weight of the portion above, yet here we see the lower portion failing, even though the force on it is only a small fraction of the weight of the portion above. This lower portion was not damaged by plane impact and not affected by heat, yet it is only resisting with a force of about a tenth of its design strength. Only explosives can account for this incredible loss of strength.

David Chandler’s explanation of this is summarized here.

Having deduced, by a scientific studyof the video evidence, that explosives were used in a top down sequence, it becomes apparent that the rate of collapse would have been under the control of the perpetrators by timing the sequence. It seems likely that the rate was chosen to be substantially lower than free fall in order to have the debris falling a little ahead of the collapse front, thus obscuring the dust puffs from the explosives. This was successful with WTC 1 except at the very top, as shown in the photos and videos. In the case of WTC 2 it was not so effective and at least three rows of dust puffs can be discerned in this video before the expanding dust cloud totally obscures the area.

Jim Hoffman has studied this collapse carefully and shows that the explosion bursts are occurring on every fourth floor. This is clearly shown in frame 147 in this set. We cannot tell whether the same spacing was used further down where the dust blocks the view.

The "spire" stands for a few seconds in clear air.

The "spire" stands for a few seconds in clear air.

Shortly after the main collapse an extraordinary event occurred. The dust that was generated by the collapse proved to be so dense that it fell vertically within a few seconds. This appears to confirm that this is not ordinary dust but is the location of most of the concrete. We can see the sky clearly over the base of the building. This heavy dust, falling rapidly, provided the energy to hurl the dust outward in the great rolling clouds that are now so well known.

We also see that the collapse is not complete. A portion of the core remains standing, often called the “spire”. It is not merely balancing there, as videos show that it sways back and forth, indicating that it is attached at its base. Maximum stress at the base would exist at the extreme positions of the sway. Having survived the countless impacts of the collapse, and also the sway, one would think that it would stand permanently, but it does not.

The "spire starts to move down vertically.

The "spire" starts to move down vertically.

Moments later the steel starts to fall vertically. This indicates that the steel had been cut through at a point well above the ground. As the steelwork is no longer falling around it there is no reason why this should happen, so this final stage of the collapse cannot be attributed to impact from material falling from above, as in the official theory. It appears that an explosive charge must have gone off rather later than intended.

Once again we see that the official explanation for the collapse is proved false by scientific examination of the recorded evidence.

4 Responses to The Twin Towers

  1. Simon says:

    “At any point in its height, it was capable of supporting several times the weight of the portion above, yet here we see the lower portion failing, even though the force on it is only a small fraction of the weight of the portion above. ”

    You’re failing to take into account the momentum and hence the force of a falling (and therefore accelerating) mass compared to that mass at rest.

    Here’s a simple experiment for you to try:

    1) Place your hand on your desk, palm down, and rest a brick on the back of your hand. You can feel the weight of the brick, right? The force of gravity is keeping the brick pressing on your hand.

    2) Now lift the brick two feet above your hand and drop it.

    3) How does your hand feel now? The weight of the brick didn’t change, but what about the force?

    4) Now think about momentum and how it relates to force, and think about the top portion of a skyscraper at rest versus that same portion in motion.

    • Frank Legge says:

      Thanks for your comment Simon. If you are not convinced by the explanation presented by David Chandler, perhaps you should look at the paper The Missing Jolt: a Simple Refutation of the NIST-Bazant Collapse Hypothesis by G MacQeen and A Szamboti, Apr 2009.

      What you appear not to have taken into account in your mental experiment with the brick, is that the brick would slow down drastically when it hits your hand. It is the deceleration of the brick which provides the energy which hurts or damages your hand. In the case of the falling top of the towers, in contrast, there is no sign of deceleration so very little energy was given up and hence very little force could have been applied by the two parts against each other.

      A more useful mental experiment with the brick would be to imagine that your hand is not on your desk but simply held out horizontally when you drop the brick on it. I think you will find that your hand accelerates considerably while the brick barely slows. The brick is slowed very little because your hand provided little resistance. That would be like what happened in the towers – the lower section, unheated and undamaged, provided very little resistance. What could account for that?

  2. Paddle says:

    Scale tests will always be a problem with this as when objects become larger the physical properties that stop things falling become disproportionate to their weight. This is mostly to do with surface area (which scales in a liniar fashion) vs volume (which scales exponentialy). [snip]

    You are right that scale models are flawed but it is because strength scales to the power of 2, while mass and volume scale to the power of 3.

    There is also the claim [by David Chandler] that a falling object would impart less force than a stationary object. The simple mistake that happened here is that the force of the fall was in adition to the objects weight.

    No, there is no mistake. Remember the equation F = Ma where F is force, M is mass and a is acceleration. The mass is of course constant. If falling freely, it will fall at the acceleration due to gravity, 9.8 m/s/s. If we observe an acceleration less than that, we know that the downward force is less than the force of gravity, so something must be pushing up on the falling mass. The tower below the falling mass must have been pushing up while it was collapsing. As David shows, the tower below was pushing up with a force about 10% of its design strength. Of course there is nothing which can make steel suddenly that weak so the steel must have been severed by explosives. Once you allow that, then you can see that the acceleration can be controlled by the timing of the charges.

    After reading the missing jolt, two reasons come to mind for their being no jolt of movement. The first is that this is an inelastic collision (even though he mentaions that that doesn’t matter). [snip]

    So you are saying that there were jolts but they couldn’t be seen. Now if that were true, the jolts would be destroying the top block at the same rate as the lower part of the tower was being destroyed. As there were only 13 floors above, there could have been no more than 13 jolts, so the collapse should have quickly stopped. It did not, proving that explosives were used.

    The second reason is that when the tower collapse began, there was ….essentialy [] a crumple zone between the block that fell and the tower, once again removing any visible jolt.

    The same argument applies – the collapse should have stopped.

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