Magdeburg hemispheres experiment

To prove the atmospheric pressure, in 1654 Otto von Guericke created a vacuum with the Magdeburg hemispheres for the first time in history. Two teams of horses (8 on each side) could not separate the two hemispheres from which he had evacuated the enclosed air. The weight of the outside air holds the metal hemispheres together. Today this experiment was demonstrated again at the annual Kaiser Otto Fest. It was quite spectacular.