First I will answer that oft-repeated question: Where were you when you heard/saw the news?
Me? It was about 7 in morning here and Dad woke me up saying that two planes had crashed into the WTC and knocked them down. I, hoping to sleep in since I was on exam leave (as I am now).
I got up, and when I came into the kitchen I was confronted with this endless repeating of these planes flying into the WTC towers, from every camera angle, over and over again.
It was a sick feeling. And then, the people that were falling from the towers, trying to escape, I was reminded that there is nothing that the media won't cover. It was horrible, but I was transfixed, and that day I did all my biology study in front of the TV, even if the reports were repeats. I swear I heard the CNN report on Bin Laden at least ten times that day. I kept all the newspapers from the day, and the magazines like Time and Newsweek.
Even though many lives were lost, it's in my opinion that something like that had to happen. The US's eyes were opened to the fact that things were very shaky in the Middle East, particularly Afghanistan, and that they had to step in and fix things up. And that was a very important move. It's a shame that it had to happen at the cost of so many innocent civilian lives, but it needed to happen. The US needed to know that what other people thought of them wasn't necessarily positive.
No doubt that it's changed the world. They talk 'post 9/11 and pre 9/11'. I mean....it was almost like the sinking of the Titanic in 1912. It proved the notion that nothing is invincible, even a great and powerful country like the United States, and that change was needed in order to prevent something like that happening.
Anyway, that's my two cents on the matter.