”The basis of science are observations.” This video shows the northwest corner of the North Tower (WTC1) with good details. The video repeats in an ”endless loop” while narrator guides the viewer through a series of observations. We see the building material being forcefully thrown out of the building, from different heights, at the same time. We see heavy building parts thrown out horizontally at high speed, followed by a cloud of dust and debris. We see the beams and framework of the building fall while leaving trails of white smoke behind it, all the way down. We do not see any ”drifting weight” crushing the building; the destruction continues until it reaches the top of the building. We see everything except the steel being reduced to fine powder. Most of David Chandler’s videos involve measurements and analysis data, but this simple exercise in pure observation helps to the analysis in context.