Introduction

What caused the destruction of the World Trade Center Twin Towers and Building 7 on September 11, 2001? More than a decade later, this question continues to be discussed by many people around the world.

According to the official explanation, the World Trade Center Twin Towers (WTC 1 and WTC 2) collapsed due to damage from airplane impacts and ensuing fires, while World Trade Center Building 7 (WTC 7), a 47-story skyscraper also in the World Trade Center complex, collapsed completely and symmetrically into its own footprint due to office fires ignited by debris from the earlier collapse of WTC 1. Though few people have studied it closely, a majority of the public, including most architects, engineers, and scientists, accept the official explanation.1

Much of the public, however, including a considerable number of architects, engineers, and scientists, do not accept the official explanation.2 3 Among those who reject it, the most common explanation is that WTC 1, WTC 2, and WTC 7 were destroyed in a procedure known as “controlled demolition,” whereby carefully placed explosives or other devices are detonated to bring down a structure in a desired manner. September 11, 2001, aside, every total collapse of a steel-framed high-rise building in history has been caused by controlled demolition.

According to this second explanation, the demolition of WTC 1, WTC 2, and WTC 7 would need to have been prepared before September 11, 2001, by demolition experts who had unrestricted access to the buildings. This explanation also implies that the demolition was planned in coordination with the other attacks of that day. Most importantly, if the goal were to make it appear that the airplanes had caused the destruction of the buildings, it could not be left to chance that airplanes would successfully crash into WTC 1 and WTC 2. This explanation, therefore, contradicts the official account of 9/11.

What Does Science Say?

The purpose of this booklet is to provide a careful examination of these competing explanations — which we will refer to as “hypotheses” from this point forward — and a comprehensive overview of the available evidence, so that readers can begin to evaluate which of the two hypotheses is more consistent with the evidence. Because this booklet only skims the surface of this subject, readers are strongly encouraged to study the official reports and the papers referenced herein before reaching their own conclusions.

The position taken in the following chapters is that very little of the evidence can be explained by the hypothesis of fire-induced failure and that all of it can be explained by the hypothesis of controlled demolition. Nonetheless, this booklet will make the best attempt to describe how the authors of the official reports have explained the evidence according to their hypothesis. In many cases, however, we will find that the authors of the official reports denied or ignored the available evidence.

In the end, the goal is to move our collective understanding of the World Trade Center’s destruction beyond misinformation so that we as a society may arrive at an accurate account of one of the most important events in our recent history.