Illustration of the interior of the Soviet satellite Sputnik 1. This spacecraft, the first ever spacecraft to reach Earth orbit, was launched on 4th October 1957 by the Soviet Union. It was a highly polished aluminium alloy sphere, 58 centimetres in diameter, with four long antennas attached to it. It transmitted radio signals back to Earth for a period of 23 days. Sputnik 1 burned up as it re-entered Earth's atmosphere on 4th January 1958. The launch of Sputnik 1 took the USA by surprise, starting what became known as the Space Race between the USA and USSR.