Terrella

Kristian Birkeland's magnetised terrella. In this experiment, he noted two spirals which he considered may be similar to that of spiral nebulae.[1][note 1]
An example of an active terrella

A terrella (Latin for 'little earth') is a small magnetised model ball representing the Earth, that is thought to have been invented by the English physician William Gilbert while investigating magnetism, and further developed 300 years later by the Norwegian scientist and explorer Kristian Birkeland, while investigating the aurora.

Terrellas have been used until the late 20th century to attempt to simulate the Earth's magnetosphere, but have now been replaced by computer simulations.

  1. ^ Birkeland, Kristian (1908–1913). The Norwegian Aurora Polaris Expedition 1902-1903. New York and Christiania (now Oslo): H. Aschehoug & Co – via archive.org. out-of-print, full text online


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