The Story of the Magdeburg Hemispheres

In 1654, Otto von Guericke, the Mayor of Magdeburg (Germany) performed a startling experiment.  Von Guericke, who also served from time to time as a diplomat and as an engineer, had been interested in science since the time that he had studied law, as a much younger man.  Since those days, he had kept up to date with the latest scientific discoveries. 

He invented a pump that would pump air, instead of water, and began to experiment with air and the effects of a vacuum.  He demonstrated that fruit could be preserved if placed in a vacuum, and that a flame could not burn in a vacuum.

 At first, von Guericke used wooden barrels for his experiments with vacuums, but he soon discovered that they imploded!  He switched to spherical, metal containers to avoid this problem.

 Von Guericke resolved to do something spectacular for Emperor Ferdinand III.  He had two bronze hemispheres built in his home town of Magdeburg.  Each had a diameter of twenty-two inches.  As a crowd (and the Emperor) looked on, von Guericke placed the two hemispheres together.  Between them was an airtight ring of leather soaked in oil and wax.  A bronze sphere was the result.

 Using his air pump, von Guericke removed the air from inside the hemispheres.  Then, he called for horses …

 Two teams of six horses were hitched to the sphere, one team at each end of the sphere.  When von Guericke gave the word, the drivers urged the horses to pull, and both teams strained to separate the hemispheres.

 Try though they did, the two teams of horses could not separate the hemispheres.  (Later, von Guericke used teams of eight horses, with the same result.)

 When the horses had been taken away, von Guericke opened a valve on his hemispheres, there was a hissing sound as air filled the bronze sphere, and the two hemispheres fell apart, virtually unaided.

 Otto von Guericke knew a great deal about the pressure that air exerted.  He knew that it pressed down with almost fifteen pounds of pressure on every square inch of the hemispheres.  His calculations had shown that it would take a force of over 22,000 pounds to separate the hemispheres!

 Von Guericke is remembered to this day.  The Otto von Guericke University of Magdeburg was named after him and Magdeburg’s city logo (”The City with Traction Power”) features a representation of his hemisphere experiment.  A statue of von Guericke, the hemispheres at his feet, commemorates the work that this scientist undertook.

(Formula for Surface Area of a Sphere = 4πr² )

(Air Pressure at Sea Level = 14.7 pounds per square inch)