Gentlemen....
On Monday 17/9 The Times had a couple of articles relevant to this topic,the second of which concerned last week's catastrophe.
Go to
www.thetimes.co.uk/section/0,,74,00.html. Should this fail go to the home page,click on Features,then Science.
My initial reaction to the collapse of both buildings in such a short time was one of surprise.However,on today's edition of Jimmy Young's programme he interviewed a Professor of Structural Engineering (my apologies if I haven't got his Academic discipline quite correct)and he said it was a tribute to the structural strength of the buildings that they did not collapse immediately.Consequently many more people survived than might have done.
On a personal note,I have given much time over the past week to try and comprehend what motivated these people to do what they did.I am no nearer to an answer.
My condolences to all concerned.