Excellent!

Yes, I had it running through my mind that a top section should only be able to demolish as much volume underneath as the volume of the top section itself .... but then I figured, "gravity?" After all, this WOULD be true if one tractor trailer met another one of equal mass and velocity on the highway: the two would come to a complete stop and destroy each other. But there's no gravity involved on a horizontal collision.

I'm still not sure he's completely correct either, because ... if you dropped that top section down from 500 feet, you CERTAINLY would have more destructive energy than if it dropped through 4 floors of 10 feet each.

But ya know ... when you watch that north tower collapse, you DON'T even see it DROPPING; it just kind of "sags" down, doesn't it. And if you take a frame by frame look at it, the top DOESN'T crush the bottom; it simply shortens itself as it goes down ... until it's about half its original height ... and THEN the bottom begins to come down as well. It looks phony as hell when you do an extreme slow motion of it.

-Vince