411 REFERENCE · Wiktionary
Magdeburg hemisphere
Reference material by Wiktionary contributors. This retains its source identity and is not 411 news reporting.
English
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Etymology
They were designed by Otto von Guericke, a German scientist and mayor of Magdeburg, in 1656.
Noun
en historical Either of a pair of large copper hemispheres, with mating rims, that were used to demonstrate the power of atmospheric pressure. When the rims were sealed with grease and the air was pumped out, the sphere contained a vacuum and could not be pulled apart even by teams of horses.