A satellite is any object that travels around a larger object. The moon is the biggest satellite orbiting the Earth. More than 3,500 man-made satellites circle the Earth as well. When the first satellite, Sputnik (SPOOT-nik) was launched by the Soviet Union on Oct. 4, 1957, no one knew how much satellites would change life on Earth. People quickly began to realize some possibilities. Today, you use satellites whenever you watch TV, call long-distance, cruise the Internet, or listen to a weather forecast. See PDF to learn some of the ways humans put satellites to work.