The space age began in 1957, when the Soviet Union launched Sputnik, the first artificial satellite to circle the earth. In 1961, Soviet cosmonaut Yuri A. Gagarin became the first person to travel in space, when he circled the earth in a Soviet spaceship. In 1969, United States astronaut Neil A. Armstrong became the first person to set foot on the moon. During the l970's, cosmonauts and astronauts for the first time lived in space aboard space stations. In l981, the United States launched the manned space shuttle Columbia, the first spaceship that could be reused and the first spacecraft that could land at a regular airfield. Scientists have used unmanned vehicles known as space probes to study planets, the sun, the moon, asteroids and comets, and other features of outer space.
