On this day in 1957, the Soviet Union launched Sputnik, the world’s first artificial satellite. It was a 58 cm (23 in) diameter polished metal sphere, with four external radio antennae to broadcast radio pulses. The Soviet Union launched it into an elliptical low Earth orbit on October 4, 1957. It was visible all around the Earth and its radio pulses detectable. This launch marked the beginning of the Space Race, where the United States and the Soviet Union competed rapidly to develop new space technology.
The satellite traveled at about 29,000 kilometers per hour (18,000 mph), taking 96.2 minutes to complete each orbit. It transmitted on 20.005 and 40.002 MHz which were monitored by amateur radio operators throughout the world. The signals continued for 22 days until the transmitter batteries ran out on 26 October 1957. Sputnik 1 burned up on 4 January 1958, as it fell from orbit upon reentering Earth’s atmosphere, after travelling about 70 million km (43.5 million miles) and spending 3 months in orbit.
Image source: Sputnik 1 – http://i.space.com/images/i/000/022/356/i02/sputnik-1-nssdc.jpg?1349209213
Image source: Sputnik 1 exploded view – http://i.space.com/images/i/000/022/354/i02/sputnik1-exploded-view.jpg?1349207735