A period between about ad 1450 and 1550 when activity on the Sun seems to have been unusually low, as judged from historical records of naked-eye sightings of sunspots and aurorae, and from measurements of carbon-14 in tree rings. The Spörer minimum and the similar Maunder minimum coincide with a period of lower temperatures on Earth known as the Little Ice Age. It was discovered by the American solar physicist John Allen (‘Jack’) Eddy (1931–2009), who named it after G. F. W. Spörer.