How?

[kyrielle]

I don't know how long this link will be good. I posted it in a comment elsewhere, in response to the question of why/how the towers collapsed, with the location of the impact. Here's the analysis I found (was directed to, by whom I no longer recall), for however long the link works:

http://www.salon.com/news/feature/2001/09/11/collapse_background/index.html