This is going to be somewhat different. Instead of a despatch from another world, I'm going to look at this from our world. I could have chosen many other September 11ths (1857 and the Mountain Meadows Massacre, 1897 and the fall of the Kingdom of Kaffa, 1921 and the settling of the first Moshav in Palestine, 1926 and the attempted assassination of Mussolini, 1945 and the Liberation of Batu Lintang, 1973 and the Murder of Allende)... but with this Blog being only a few days old, nothing but 9/11 THE 9/11 makes sense.
So... what might have changed if 9/11 had not happened?
First of all, thousands of people would still have been alive, not only the immediate victims but those caught in the aftermath. Certainly 7/7 would never have happened in London, neither would the war in Afghanistan. But on the other hand, there would not have been a wave of sympathy for the victims that showed many in the world for their fundamental decency.
On the other hand, it seems obvious that neither Libya nor the IRA would have renounced terrorism except in revulsion at the events of 9/11. Colonel Gaddaffi saw immediately that Terrorism had become impossible as a tactic in warfare once this act of mass murder had been committed. He also ended Libya's chemical weapons program and invited inspectors in to see that it was dismantled.
For good or ill the murder of nearly 3000 people that day has changed the world utterly. It is only nine years ago, but we know already that it will be remembered for a long time to come, because an attack on New York City is an attack on the whole world.