[II2II]

Funny story there: I was stuck with a conspiracy-minded high school teacher who insisted that some sort of flash lower down in one of the towers was proof of a demolition. I got fed up with listening to it each day, so I calculated how long it would take a shock wave to propagate through steel, from the crash site to the flash below. It pretty much worked out.

[noman-land]

What was the teacher's reaction?

[II2II]

From my recollections, not much. I was on a practicum in his classroom, so it was different from the usual teacher/student dynamics. It was a great teachable moment though!

[nullorempty]

Congrats. You solved the puzzle.