The use of science and engineering is critical to understanding what happened. Voluminous evidence supports several key facts about the attacks of 9/11.
The destruction of the Twin Towers and WTC Building 7 were not gravity-only collapses due to structural trauma and fires.
The damage at the Pentagon can only be explained by a large momentum impact by an object with the dimensions of a Boeing 757. No evidence of damage that can be solely attributed to explosives has been identified.