Sally Kristen Ride was an American physicist and astronaut. Born in Los Angeles, Ride joined NASA in 1978 and, at the age of 32, became the first American woman in space. After flying twice on the space shuttle Challenger, she left NASA in 1987. She worked for two years at Stanford University's Center for International Security and Arms Control, then the University of California, San Diego as a professor of physics, primarily researching non-linear optics and Thomson scattering. She served on the committees that investigated the Challenger and Columbia space shuttle disasters, the only person to participate on both. Ride remains the youngest American astronaut to travel to space.