Magdeburg Hemispheres

Magdeburg hemispheres are a pair of copper hemispheres from one of the famous experiments performed between 1654 and 1663 by O. Guericke. He removed the air out the copper hemispheres to make them fit together and sealed them with grease at their rims in such a manner as to form a hollow copper spherical vacuum. He then showed that two teams of horses, harnessed to each sphere in opposite directions, could not pull the hemispheres apart. Guericke’s demonstration was first performed in front of the Reichstag and Emperor Ferdinand III in Regensburg. Thirty horses, in two teams of fifteen, could not separate the hemispheres until the vacuum was released.