JAN. 28, 2013
Teacher Christa McAuliffe and theChallenger Explosion
Challenger
Many people remember what they were doing on Jan. 28, 1986, when theChallenger space shuttle, which was carrying seven astronauts (meet the crew), including S. Christa McAuliffe (pictured back row, second to the left), exploded about 10 miles above Earth. McAuliffe, a social studies teacher from New Hampshire, had been selected to join the mission and teach lessons from space to schoolchildren around the country. Following the disaster, it was determined that two rubber O-rings, which separated sections of the rocket booster, failed to seal properly due to cold temperatures on the morning of the launch.

Several months later, theoretical physicist Richard Feynman, a member of the commission exploring the causes for the disaster, famously demonstrated how the O-rings became less resilient and subject to seal failures at ice-cold temperatures. Feynman later wrote about the investigation, including NASA's overly optimistic approach to safety measures, in his 1988 book What Do You Care What Other People Think?