So how should they have "reacted" when hit by two 747's? What exactly would have been an acceptable collapse or implosion? Toppling over to the side? If they would have done that I'll bet people would've been talking about how poorly designed they were and conspiracy theorists would have said that someone detonated a bomb at the base to cause the topple.

It seems to me that they reacted perfectly to their design and that is to pancake on top of itself to minimize damage to surrounding buildings in the event of collapse. No? Does it not make sense that as the core columns succumbed to the extreme heat they would have, through connection of intermediate members, pulled the exterior steel "panels" inward thus creating an implosion effect. Then as the thousands of tons of steel, concrete, framework, office furniture, etc. came crashing down on lower floors the implosion would continue.

The tremors? Have you ever heard steel snap? Have you ever heard a large steel member dropped or even just hit really hard with a large hammer? If so I bet you'd agree that there may be a small "tremor" associated with the sound, since sound waves can cause small tremors or better yet cause a small video camera to shake a little. Imagine dozens of large steel members all snapping at once while the building is collapsing. Think that might be "felt" a block or so away?

I haven't seen it mentioned here but you have before mentioned the explosions heard before the collapse and I can't pass up the opportunity to throw this in as well. Just to let you know, in case you didn't, buildings have mechanical equipment all throughout that will explode when subjected to extreme heat. You know, like the heat caused by thousands of gallons of jet fuel burning. This is a pretty neat video of an electrical transformer exploding. There are also things like mechanical compressors or even fire extinguishers that can explode in extreme heat.

Carlos