You will notice this sort of thing more and more as time goes on.<p>For me the &quot;ah hah&quot; moment was when it hit me that &quot;Where were you when you heard about Challenger?&quot; was my generation&#x27;s version of, &quot;Where were you when JFK was assassinated?&quot;<p>Another easily observed one is music.  Very few people are aware of much that happened in popular music after they hit 25.