This video is informative, and on the right track. I hope new sets of experiments more closely mimicking the collapses of the towers can be made that will be more convincing. Let's say I drop an egg on a load of eggs. What will happen? Let''s say I drop a cinderblock on a feather. Will there be measurable deceleration of the block? I think some of these arguments need to be refined to focus on the structures and their likely reactions to falling objects. An egg falling on a sidewalk from eight stories will show little resistance. Still, I like this video. Much work needs to be done in this area, but the presentations are getting better and better.