Dave Heller of Berkeley, CA wrote:
To Anders of Taarbaek, Denmark:

If you're a mathematician, you should have no problem proving the collapses were due to fire and gravitational forces. The speed of the fall, about as close to free fall in a vacuum you can get without actually being in a vacuum, leaves no room for any other energy.

That means that there is no energy to throw massive beams hundreds of feet into adjacent buildings, there's no energy to pulverize most of the concrete into talcum powder like dust and there's no energy to even break all the thousands of weld joints and nuts and bolts holding the towers together.

I just did a radio interview with Professor Judy Wood of Clemson University who did an analysis of the towers collapse based on my article. Her article is a little more technical than mine, but should help you clarify any doubts you have.

Professor Wood holds a PhD and teaches materials science at Clemson. Oddly, her colleagues don't dispute her science, just the obvious conclusions she makes from it.

Anders, I encourage you to get my email address through Tony if you would like to discuss this further. Also, Professor Wood (if that's really her ;-) )has her annonymous email address on the billiard ball site and I'm sure she'd be pleased to assist you as well.