September 11 attacks ?!?! (911)?

sooo i just watched a sh!t load of youtube videos about 911 and now i want to knoo more ! like did bush plan 911? did he know anything about it before it happened ? IF THE PLANE HIT THE TOP OF THE BUILDING WHY DID THE BOTTOM COLLAPSE ??? and that whole "flip the 20 dollar bill" thing where it shows the burning twin towers thing ?!?! this is trippy !! our world sucks !!! haha but anyways just say whatever you think. all opinions are accepted