An 18-month period, from 1957 July to the end of 1958, in which world-wide collaborative observations were made to study the connection between solar flares, geomagnetic disturbances, radio fade-outs, and particle emission from the Sun. The IGY was designed to coincide with maximum sunspot activity, which turned out to be the largest recorded since the invention of the telescope, and resulted in a greatly improved picture of solar–terrestrial relations. Sputnik 1, the first artificial satellite, was launched during the IGY by the Soviet Union.