Popular conspiracy theories (continuation of thread hijack)
 

Read this first

Conspire, the show specifically addressed that point. A number of engineers said those puffs were actually windows, concrete and drywall being blown out. They said as the building fell, the energy compressed the air in the lower floors. As the air compressed, it began to blow out windows. The floors disintegrated under this pressure before the higher floors got to them.

I'm no structural engineer, but that seems to make sense.

Re: Popular conspiracy theories (continuation of thread hijack)
 

A shock wave can certainly break stuff below what is being hit. A wave of energy can be just as destructive as a piece of matter.