The start of the space age can be dated from two separate events towards the end of World War Two. First was the development of rockets that could escape the Earth's atmosphere - and with it, the potential to fire objects into orbit.
The second was the realisation that those orbiting objects - called satellites - could be used as reflectors to bounce signals around the Earth...
The first steps towards the technology of modern rocketry were taken by the American Dr Robert Goddard and by the German Werner von Braun in the 1920s and 1930s. Both were trying to perfect liquid-fuelled rockets - but it was von Braun who would ultimately be successful.
During the Second World War, von Braun and his fellow German scientists tried to perfect a rocket to carry out long-range bombardment of English cities.
Their principal version was the Aggregat 4 (A4) - which became notorious as Hitler's V2 or 'vengeance weapon'. The first two launches ended in failure but the third try, on October 3, 1942, saw a V2 lift off from its Baltic island launch pad, follow its programmed trajectory and land perfectly on-target 193 kilometres (120 miles) away. On the way it had risen 60 miles - beyond the outer edges of the Earth's atmosphere. So, this date can be said to mark the beginning of the space age.
Once Werner von Braun's V2 missiles ceased raining destruction on London and other cities, a young RAF technician called Arthur C. Clarke conceived a vision for the post-war future in a magazine called Wireless World.
In a letter headed 'V2 for Ionospheric Research', Clarke explained how a network of satellites could be placed in stationary orbit, 22,300 miles above the Earth's surface.
Later, in an article titled 'Extra-Terrestrial Relays' published in October 1945, Clarke explained how these satellites could be used to transmit radio, TV and telephone signals around the world.
The notion of the geostationary (or geosynchronous) orbit was first proposed in 1945 when the science fiction writer Arthur C. Clarke published his visionary concept of relaying communication signals from one ground station to another via artificial satellites circling the Earth.
Keeping a steady flow of information between two ground stations and the satellite would need the satellite to remain in a fixed position in sight of both stations.
Clarke reasoned that if the satellite orbited in the same direction and the same orbital speed as the Earth's rotation, it would appear to remain in a fixed position in the sky.
He correctly calculated that the satellite would exactly match the speed of the Earth's rotation and keep in constant orbit at an altitude of 35,800km (22,300 miles) above the equator.
The first communications satellite to be placed in this type of orbit was Syncom 2, launched by NASA in 1963. Most of those that followed were also placed in geosynchronous orbit.
