9 - 1 1 R e s e a r c h essays

Controlled Demolition
of the WTC Twin Towers:

A Review of Arguments, Evidence, and Theories

Jim Hoffman
Version 0.9, Oct. 26, 2006


Many people suspected that the Twin Towers were demolished the moment that they watched the event. I've talked to dozens of people who say they knew as soon as they saw the buildings come down that they were demolised and that they story collapse story being supplied by the news anchors was false. At least one website published a controlled demolition scenario within two days of the attack. Now, more than five years later, the question of whether the three WTC skyscrapers were subject to controlled demolition is the subject of heated debates spanning a wide range of arguments and claims.

Today there are numerous books, dvds, and websites and webcasts that purport to support the demolition allegation with a variety of evidence and claims, but few make a systematic analysis of the evidence. In this essay I will attempt to fairly categorize and summarize the most salient arguments for controlled demolition and the evidence they rest on. I will further review some of the more common theories about how the demolitions may have been engineered, and explain how theories of demolition relate to arguments for and against demolition.




Theories and Hypotheses

In science a hypothesis is a --- whereas a theory is a --- A theory is supported by more evidence than a hypothesis, which is inverse of the vernacular use of 'theory'.

The term conspiracy theory is usually used to ridicule an idea. Thus, describing the idea of demolition of the Twin Towers as a hypothesis, as Steven Jones did on MSNBC's The Situation, gives it an air of credibility. Casting the idea as a "hypothesis to be tested" casts it in more objective light than describing it as a theory.

Controlled Demolition

The term controlled demolition conjures up images of buildings folding in on themselves, and for those who have seen documentaries, drilling, cutter charges, and hundreds of feet of detonation cord. Controlled demolition really means the engineered destruction of structures, of which buiding implosion is just one type.

The description of the Twin Towers' destruction as controlled demolitions is dissonant because the balooning debris clouds that consumed the Towers don't look very controlled. However, they were very controlled in many aspects:

In regard to the fate each of the Twin Towers, there are only two possibilities:

  1. The Tower underwent a gravity-driven collapse due to plane-impact and fire damage: it was a natural or spontaneous event.
  2. The Tower was destroyed through the timed destruction of structures by explosives or other devices: it was an engineered event.

Although there are some fanciful ideas that would challenge this dichotomy, I maintain that it describes an essential fact: If the falls of the Towers were not natural or spontaneous events, then they had to be controlled demolitions.

Evidence for Controlled Demolition

The term demolition evidence is often often used loosely without attempting to establish how it fits into specific arguments for the demoltiion of the Twin Towers. In this essay I'll first review and classify evidence cited by arguments and claims for controlled demolition of the Twin Towers. I'll defer consideration of the arguments and claims themselves to the next section, and in this section consider the evidence in isolation.

Evidence varies widely in its reliability. At one extreme are multiple photographs with good resolution showing an event from different vantage points. At the other are isolated second-hand reports from people claiming to have witnessed the event.

Types of Evidence

Photographs and Videos

Photographic and video recordings of the events in New York City on 9/11/01 and their aftermath provide a wealth of information

Witness Testimony

Engineering History

WTC Performance Documents


Experiments constitute a body of evidence that is not limited to the artifacts that survived the attack and clean-up operation.

Quality of Evidence

Applicability of Evidence

Arguments for Controlled Demolition

In this section I classify, summarize, and critique arguments and claims that have been made for controlled demolition of the Twin Towers. I will review a variety of arguments that range from proofs to flimsy claims that I grudingly designate arguments in order to characterize them..

Inductive and Deductive Arguments

Logical arguments can be broadly dived into two categories: inductive and deductive. An indictive argument proceeds from specific observations to more general conclusions whereas a deductive argment applies general principles to draw specific conclusions conclusions.

Scope of Arguments

Arguments can be characterized by their scope. Arguments for controlled demolition either cite direct evidence of the demolition or attack the collapse theories that constitute the alternative to demolition.

General Collapse Theory

Implicit Collapse Theories

Explicit Collapse Theories

A number of theories of the collapse of the Twin Towers are explicitly articulated by official government reports.

Column Failure Theory

The column failure theory was articulated in an artcle in the Journal of Engineering Mechanics ASCE just two days after the attack.

Floor Pancake Theory

The floor pancake theory was the officially accepted theory until it was supplanted by NIST's new theory in 2005.

NIST's Theory

Principle Arguments

Inductive Arguments

Demolition Features

Engineering History

There are a set of arguments on observations about the history of steel-framed buildings subjected to fires and other structural damage.

Deductive Arguments

There exist a substantial number of deductive arguments for the controlled demolition of the Twin Towers. These show that specific features are incompatable with the the first possibility -- that each tower was spontaneously collapsed. Most of these arguments are applicable to both Towers with some being specific to one Tower or the other.


The destruction of each Tower was characterized by a high degree of radial symmetry about the Tower's vertical axis.


The thorough pulverization of the contents of the Twin Towers is one of the most striking features of their destruction.

Explosive Events

South Tower Top Motion

North Tower Mast Drop

Jets of Gas and Dust

Energy Flow Analysis

Demolition Theories and Claims

A number of unscientific claims that have the effect of diluting and discrediting the clear case for controlled demolition.

Core Attack Theory

Thermobarics Theory

The Basement Bombs Theory

Claims about Pre-Collapse Seismic Spikes

Claims about Pre-Collapse Ground-Level Explosions

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