He's only a high school physics teacher, but if you watch the youtube video, David Chandler made NIST (National Institute of Standards and Technology) look silly, first saying that free fall couldn't have happened in the collapse of WTC7, then revising their report and admitting that free fall did occur. Of course, they didn't revise their computer model, which doesn't show free fall, nor explain how it could have happened. So when people say that you must have engineering background before you can doubt the official account of the WTC collapses, perhaps you could suggest that they take a high school physics class.
NIST Finally Admits Freefall, Part II
NIST Finall Admits Freefall, Part III