It was 29 years ago today that the Space Shuttle Challenger exploded. Twenty-nine years. I still remember it vividly. As a third-grader at Elmer Thienes Elementary School, we were all gathered around TVs to watch the launch because Christa McAuliffe, a teacher, was set to be the first civilian in space. The shock of the explosion is something that has stayed with me over the intervening three decades; it was the seminal moment of my -- and, I suspect, many peoples' -- childhood.

President Ronald Reagan was supposed to give his State of the Union address that night.  After hearing about the explosion just before noon -- the Christian Science Monitor did a nice look-back at Reagan's day -- he scrapped that plan and instead delivered what is widely regarded as one of the finest speeches of his presidency. (You can read it here.) It was short -- 650 words and less than five total minutes in delivery -- but contains perhaps Reagan's most-quoted line: "We will never forget them nor the last time we saw them ... as they prepared for their journey and waved goodbye ... and slipped the surly bonds of Earth to touch the face of God."

President Reagan was supposed to give his State of the Union address that night, but instead spoke about about the Challenger explosion. (The Ronald Reagan Presidential Library)