The three events that come to mind, out of a tangle of so many are:
1) The Challenger Accident – 10 years old
2) The fall of the Soviet Union – 16 years old
3) The Chernobyl Accident – 10 years old
Each of these events changed the world. I remember that I was walking in the hallway of my school when the news struck. It was just the start of that whole disaster which led to the discovery that an O-Ring had failed and it pretty much stunned our space program and slowed down subsequent space missions to a crawl. I can remember seeing the explosion pattern on the TV news for weeks after the event.
The fall of the Soviet Union was next. It, in some ways, began with the fall of the Berlin Wall and lead to it's final death years later. When the Soviet Union went to the great beyond, so did the Cold War that had raged between the United States and the USSR. It was a pivotal moment in world history as two enemies suddenly stopped fighting because one simply ceased to exist. The Russian Federation appeared in it's aftermath and we never really got the Cold War started again after that. When the Soviets failed, they left a huge number of nuclear weapons floating in a sea of doubt. I still personally doubt that the Russian Federation has control over all the Soviet missiles that they established. A part of me even thinks that someday some Ukranian goat herder will blunder into a mobile ICBM trailer and wonder if the rusted out hulk is still dangerous.
The third bit was Chernobyl. It pretty much sealed the fate of nuclear power on Earth after proving that a really bad accident is really bad for everyone. Of course, we never learned our lesson with Chernobyl and so we had to learn it all over again with Fukushima.
There are other events, I"m sure, personal events that meant more to me, but these were the best world-changing events that I could come up with on the spot. These are the sort of events that you never forget. I don't put September 11th, 2001 on this list because frankly, that event upset a lot of Americans but it wasn't as vast as the events I detailed above were. Challenger, the Soviets, and Chernobyl affected everything from space travel, to global politics and safety. So for those wondering about 9/11, that's the order of importance for me.
