Barbara Morgan carries on Christa McAuliffe's mission

For some reason, we remember where we were when we heard big news. The end of World War II. The Kennedy assassination. Man landing on the moon.

The Challenger explosion was one of those instances.

And while it's been 62 years since the end of World War II, 44 since JFK was killed and 38 since that "one small step," the first space shuttle disaster is receding into the past quickly as well. Can it be 21 years already that thousands of school children watched in horror as their hero, teacher Christa McAuliffe, and the rest of the crew were killed?

Those students, now in their late 20s if not 30s or nearing 40, must be remembering where they were on that January day in 1986.

Barbara Morgan, McAuliffe's backup for that fatal flight, is in orbit now, an astronaut in her own right, assigned to operator the shuttle's mechanical arm.

But Morgan, now 55, will always be a teacher. A week into the flight, she's scheduled to speak to schoolchildren in Idaho, where she lived and taught before joining NASA?in 1998 as its first educator-astronaut.

Many say the cost of human space flight, in taxpayer dollars and human lives, is too high. They have a point. Many of the tasks today's astronauts perform could easily be accomplished by robots at a much lower costs.

But humankind have never been content to stay at home while there are challenges to be met and knowledge to be gained.

Those students who watched those horrible smoke trails above the Florida sky all those years ago have gone on to gain knowledge, meet challenges and have children of their own.

The inspiration provided by teachers like Barbara Morgan -- and Christa McAuliffe before her -- is invaluable.