The Magdeburg hemispheres were designed by German scientist and mayor of Magdeburg, Otto von Guericke in 1654 to demonstrate vacuum and the concept of atmospheric pressure.
The Magdeburg hemispheres, approximately 20 inches (50 cm) in diameter, were designed to demonstrate the vacuum pump that Otto von Guericke had invented. One of them had a tube connection to attach the pump, with a valve to close it off. When the air was removed from inside the hemispheres, and the valve was closed, the hose from the pump could be detached, and they were held firmly together by the air pressure of the surrounding atmosphere.
The force holding the hemispheres together was equal to the area bounded by the joint between the hemispheres, a circle with a diameter of 20 inches (50 cm), multiplied by the difference in air pressure between the inside and the outside. It is unclear how good a vacuum von Guericke’s pump was able to achieve, but if it was able to evacuate all of the air from the inside, the hemispheres would have been held together with a force of approximately 9,000 lbs. (40,000 N), equivalent to lifting a car or small elephant; a dramatic demonstration of the pressure of the atmosphere.
Von Guericke’s demonstration was performed on May 8, 1654 in front of the Reichstag and the Emperor Ferdinand III in Regensburg. Thirty horses, two teams of fifteen, could not separate the hemispheres until the valve was opened to release the vacuum. In 1656 he repeated the demonstration with sixteen horses, two teams of eight, in his hometown of Magdeburg, where he was mayor. He also took the two hemispheres, hung them with a support, and removed the air from within. He then strapped weights to the hemispheres, but the hemispheres would not move. Gaspar Schott was the first to describe the experiment in print in his Mechanica Hydraulico-Pneumatica (1657). In 1663 (or according to some sources in 1661) the demonstration was given in Berlin before Frederick William, Elector of Brandenburg with 24 horses.
WEC Institute’s Magdeburg Hemisphere for 2011
The experiment became a popular way to illustrate the principles of air pressure, and many smaller copies of the hemispheres were made, and are used to this day in science classes. Re-enactments of von Guerike’s 1654 experiment are performed in locations around the world by the Otto von Guericke Society. On the 18th of March 2000, a demonstration using 16 horses was conducted in Great Torrington by Barometer World.
Detroit Seminoles semipro football team attempt to separate the hemispheres
The WEC Institute was asked to assemble a modern Magdeburg Hemisphere for demonstration and testing purposes for a new television series. The above hemisphere was tested on September 20, 2011 at Seaholm High School, Birmingham, Michigan by the Detroit Seminoles semipro football team. They were unable to separate it.
WEC Institute Magdeburg Hemispheres #1 Specifications:
Construction Material: Aluminum
Size: 20 inches (50 cm)
Separation Force: 9,000 lbs (40,000 N)