The fall of the Twin Towers of the WTC has been the subject of a series of expert discussions on the mechanism by which the fall took place, and especially its speed. The official NIST report states the following: "The release of potential energy due to downward movement of building mass above the buckled columns exceeded the strain energy that could be absorbed by the structure. Global collapse ensued." But how, then, is the collapse itself supposed to occur? With what acceleration? Is the fall of the upper floors supposed to accelerate or should it decelerate and subsequently stop due to...