In 1657, German scientist Otto von Guericke began an extraordinary experiment in the city of Magdeburg. Von Guericke fastened together two perfectly matching hollow bronze half spheres. Using an air pump, he then extracted the air, creating a vacuum inside the sphere. Two groups of eight horses try to separate the two halves by pulling them in the opposite direction. The audience was astonished to see how the horses were unable to break the power of the vacuum.