yesterday i saw a show on the science channel about tunnels.One method of boring into softer rock involes dilling holes,filling them with a 2 part mix of un-named liquids,which when charged w/det cords explodes violently. EUREKA!!!!THE TOWERS and#7 's fire sprinkler pipes could have been filled w/liquid explosives and detonated!!!Search google---you will see the towers originally had no sprinkler system installed---until after the 1995 bombing---which ensued up till 9/11/01. Fires in #7 reportedly could not be stopped because "the sprinklers MALFUNCTIONED"...See also suspicious men apprehended after 9/11 with anauthorize passes to lower levels "working on the sprinklers"