Otto von Guericke was born on November 20, 1602, in Magdeburg, Germany. Whilehe studied mathematics, law, and engineering, Guericke would become famous for his experiments with a vacuum and air pressure.
Following travels to England and France, Guericke returned to Magdeburg in 1627 and became a politician. Unfortunately, this was during the Thirty Years'War, and Guericke and his family had to flee the city in 1631. After the war,he returned and helped rebuild the city, becoming mayor in 1646. Twenty years later he became a noble and added "von" to his name.
During Guericke's time, scientists were involved in an argument about whethera vacuum could exist. Guericke, who believed in the Copernican theory of thesolar system, was extremely interested in understanding the nature of space.He wondered whether empty space could exist. Many scientists held on to theAristotelian theory that a vacuum was impossible. Aristotle (384-322 B.C.) rightly suggested that as air became less dense an object wouldmove faster. However, he went astray by claiming that if there wasn't any air, an object could move infinitely fast. Since he doubted the idea that infinitely increasing speed could exist, he concluded that a vacuum could not existeither.
Guericke was a rare breed of scientist who refused to accept previously heldscientific facts; he believed in experimentation. He decided to try to successfully create a vacuum. In 1647 his first attempt failed, but in 1650 he built another air pump by putting a piston inside a cylinder that had two flap valves (a model later improved upon by Robert Boyle ). He filled a cask with water to remove the air, sealed it, and used his pump to remove the water.
Unfortunately, the cask leaked air. He made a second attempt, placing the cask within another containing water. He hoped the water-filled cask would prevent air from entering the evacuated cask. He was right; air did not leak in, but water did.
Guericke decided to take another tack. He took a hollow copper sphere with avalve built in the bottom and used his pump to remove the air. The sphere promptly crumpled, proving that when the sphere was empty the external air pressure was strong enough to crush the sphere.
This is what should have happened according to René Descartes, who held that space and matter were equivalent, so a vacuum could not exist. Guericke did not agree with Descartes' assertion. Guericke tried again with a more substantial sphere. This time he succeeded in creating his vacuum. He then undertook a series of grandstanding experiments to demonstrate the power of airpressure. In one of the most famous, in 1657, he placed two copper hemispheres together and removed the air. Sixteen horses were unable to pull the two halves apart. Obviously, the external air had substantial pressure; so much, infact, that the hemispheres held together when the internal air was removed.
It is interesting to note that Guericke placed the valve at the bottom of thehemispheres because he believed that air, like water, would seek the lowestlevel. Later he found that air was distributed evenly, since he could createa vacuum regardless of the location of the valve. This led him to think aboutthe density of air decreasing as one's altitude increased. He studied variations in air pressure and, in 1660, invented a barometer, which he used to make predictions about the weather.
Another of Guericke's experiments pitted 50 men against his piston. A rope was attached to a piston in a cylinder and the men were told to pull. Guerickecreated a vacuum on the opposite side of the piston and the men were unable to keep the external air pressure from pushing the pistons into the cylinder.The force of air pressure became very important later in the development of the steam engine.
In a different vein, Guericke also invented the first mechanical static electricity generator, hinting at the future possibility of Robert Van de Graaff'sgenerator. Guericke rotated a sulfur sphere on a shaft. When it was rubbed,it built up an electrical charge that emitted sizeable sparks. Guericke did not give any special consideration to this electrical phenomenon, but during the next century others would continue to experiment with static electricity.