A satellite launched in 1958, no bigger than a grapefruit and silent since 1964, is still the oldest human-made object circling Earth — and it is expected to keep quietly orbiting overhead for another few centuries

On 17 March 1958, a three-stage rocket lifted a polished aluminium sphere from Cape Canaveral and placed it in a long, elliptical orbit around Earth. Vanguard 1 was only 16.3 centimetres across and…