Magdeburg Hemispheres Demonstration (1654)

Otto von Guericke demonstrated atmospheric pressure in 1654 using copper hemispheres before the Imperial Diet in Regensburg. The sealed spheres resisted separation by thirty horses until air was reintroduced, proving the force of the atmosphere.

Episodes

Background and detail

Background. Otto von Guericke, mayor of Magdeburg, invented a vacuum pump to demonstrate atmospheric pressure. Inspired by earlier work, he designed large copper hemispheres to visually prove the existence of a vacuum and the strength of air pressure.

The Demonstration. On May 8, 1654, Guericke performed the experiment in Regensburg before Emperor Ferdinand III and the Imperial Diet. After pumping out the air, teams of thirty horses failed to pull the hemispheres apart, illustrating the immense force of atmospheric pressure.

Resolution. The hemispheres remained sealed until the valve was opened, allowing air to rush in and equalize pressure. This allowed the spheres to be separated easily, confirming that the resistance was due to external atmospheric pressure rather than internal adhesion.

People involved

Sources

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