re: #49 Charles

When you understand the construction of the Twin Towers, it’s not hard to see how they could collapse straight down.

To simplify it a bit, the WTC towers were huge stacks of giant, enormously heavy concrete slabs, held up and apart by steel support girders. When the burning jet fuel reached a hot enough temperature to weaken the steel beams, the slabs began pancaking downwards, releasing an enormous amount of kinetic energy, pulverizing everything between them, and blowing the resulting dust out of the sides in the process.

Some of the last people who escaped just as the buildings were collapsing reported hearing the accelerating crashes as the slabs were coming down.

As inappropriate as the word seems, we’re probably damn lucky the buildings came down like that.