Zero Gravity
circa 1985: 'Teacher in Space' Sharon Christa McAuliffe and her back-up Barbara Morgan prepare themselves for the STS 51-L space mission by experiencing a brief period of weightlessness in NASA's KC-135 aircraft, nicknamed the 'Vomit Comet'. McAuliffe and her fellow crew members died when the Challenger shuttle exploded during take-off on 28th January 1986. (Photo by NASA/Space Frontiers/Getty Images)