Today, we take it for granted that we can see live TV pictures of events such as the World Cup or the Olympic Games. These pictures have often travelled to your screen from the other side of the world.
What makes this possible is a ring of communication satellites in geostationary orbit. Flying about 36,000 km above the equator, these satellites appear to hover over the same part of Earth's surface. They receive TV signals from dishes on the ground and then amplify (boost) them. The satellite then retransmits the pictures and sound back to the viewers.
The modern age of satellite TV began in July 1962, when Telstar 1 relayed the first live TV programmes from the United States to Britain. Then in 1965, Early Bird became the first satellite to be used for regular TV broadcasts between North America and Europe.
In the past, TV signals had to be sent to large dish antennas at special ground stations before being broadcast to local aerials. Today, the satellite signals are so powerful that they can be picked up by small dishes on the roofs of offices and houses. This direct-to-home digital TV has become very popular in many countries.
Live satellite links can also be set up between distant offices, or between doctors in city hospitals and patients in remote country villages. Satellites are also used for digital radio broadcasts, which can be picked up by cars and portable radios.