David Chandler (high school physics teacher):
The official story is that the North Tower of the World Trade Center collapsed due to gravity.
This has been critiqued in an analysis by Graeme MacQueen and Tony Szamboti,
and in a related analysis by David Chandler (both in the Journal of 9/11 Studies).
The Balzac-Vitry demolition was a true gravity-driven collapse.
The same analysis that was applied to the World Trade Center is here applied to this known demolition,
with contrasting results.
This analysis supports the conclusions of both papers referred to above:
the North Tower of the World Trade Center was not a natural, gravity-driven collapse.