Originally Posted by MediaGuy

Not stop it, but slowed it down. Offered some resistance. There was zero resistance. The top part that started going down had four times its mass and and conserved energy in its path. It's not like it was raised a thousand feet in the air and dropped; it had no velocity.

Even if the lower seventy floors were made of glass they couldn't have fallen so fast.

Remember the laws of motion and path of least resistance principle from science class?

Buildings can't "collapse" that way. It's physically impossible. Not without a little help.

;)