WTC building 7 was a trapezoid type of structure. The larger side of the building would be heavier and more massive. This is where column 79 was located. NIST claims that column 79 collapsed, leading to the collapse of the whole building. Column 79 was on the larger side of the building. Here's a simplified floor plan:
http://i18.photobucket.com/albums/b1.../wtc082108.jpg
Column 79 is at the lower left. NIST claims that only column 79 was destroyed in the beginning of the collapse sequence, and because the same side of the building in which 79 was located was the bigger, heavier side of the building, two different influences should have ensured that the building tilted toward the bigger end,building 7 should have tipped towards one side.
I think many folks don't understand just how tough these buildings really are. In 1999 I was involved with testing the structural integrity of the new EPA building in Sacramento. The 14th floor was stress tested by using 500 55 gallon barrels filled with water. They were placed on a large area of open floor space. Over 110 tons was applied to the floor,and it held this weight for 4 hours, it sagged over 2 feet during the test. No failure at all, everything came back into place after completion of the test, and not even a crack in the concrete. Sorry folks, I can't buy the pancake theory of the heat weakened steel. Anyone know if they every explained the traces of thermite that were found.
One thing I do know is that we will never really find out what happened.