After the Second World War, the race to develop intercontinental ballistic missiles led the Soviet Union, under Sergei Korolev, to develop the R-7 Semyorka rocket. The same thrust could reach space; once the United States announced in 1955 that it would launch a satellite as part of the International Geophysical Year, the Soviets began work on a satellite of their own. They chose a deliberately simple and reliable design: an 83.6-kilogram polished aluminium sphere, 58 centimetres across, with four trailing antennae and two radio transmitters.

On the night of 4 October 1957 an R-7 lifted off from the Baikonur Cosmodrome in present-day Kazakhstan and placed Sputnik 1 into an elliptical orbit. The satellite circled the Earth every 96 minutes, broadcasting short "beep" signals on 20 and 40 megahertz — frequencies that ordinary radio amateurs could pick up. The signal was not just a technical success but a public announcement that the sky had become political territory.

The reaction in the United States was sharp. In the period known as the Sputnik crisis, education policy was overhauled, ARPA (later DARPA) was set up to coordinate defence research, and on 29 July 1958 President Eisenhower signed NASA into existence. The Cold War turned into a space race driven by the same rocket engines as the missile programmes: on 12 April 1961 Yuri Gagarin became the first human in orbit, and on 20 July 1969 Apollo 11 landed on the Moon.

Sputnik itself fell silent after three weeks and burned up in the atmosphere three months later. But its legacy is permanent. The tens of thousands of satellites now overhead — weather, GPS, internet, global finance — all live in the orbital regime opened that night above Baikonur. If "space" has become an ordinary layer of human activity, this is its starting date.