azredscorpion (@azredscorpion)

This Kostack Studio World Trade Center simulation is useful because it strips away the smoke. In the real footage, fire, dust, debris, distance, and chaos hide a lot of the motion, so many people think the towers simply dropped straight down into their own footprints. The simulations show the collapse starting in the damaged, fire-weakened zone: the upper section begins to move and tilt, then the destruction travels downward. The towers do not vanish vertically into their footprints. Large parts of the upper structure and exterior move outward and sideways as the collapse develops—motion that the debris cloud quickly hides in the actual videos.