Otto von Guericke was born on November 20, 1602, in Magdeburg, Germany. While he studied mathematics, law, and engineering, Guericke would become famous for his experiments with a vacuum and air pressure. He died at the age of 83, in Hamburg, Germany, on May 11, 1686.
Following travels to England and France, Guericke returned to Magdeburg in 1627 and became a politician. Unfortunately, this was during the Thirty Years' War; 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 whether a vacuum could exist. Guericke, who believed in the Copernican theory of the solar system, was extremely interested in understanding the nature of space. He wondered whether empty space could exist. Many scientists held on to the Aristotelian theory that a vacuum was impossible. Aristotle rightly suggested that as air became less dense an object would move 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 exist either.
Guericke was a rare breed of scientist who refused to accept previously held scientific facts; he believed in experimentation. He decided to try to successfully create a vacuum. In 1647 his first attempt failed, but in1650 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 a valve built in the bottom and used his pump to remove the air. The sphere promptly crumpled. This showed that when the sphere was empty, the external air pressure was strong enough to crush the sphere.
René Descartes held that space and matter were equivalent, so a vacuum could not exist. Guericke did not agree with Descartes's 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 air pressure. 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, in fact, 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 the hemispheres because he believed that air, like water, would seek the lowest level. Later he found that air was distributed evenly, since he could create a vacuum regardless of the location of the valve. This led him to think about the 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. Guericke created 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, similar to Robert Van de Graaff's generator. Guericke rotated a sulfur sphere on a shaft. When it was rubbed, it built up an electrical charge that emitted sizable 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.
This is the complete article, containing 706 words
(approx. 2 pages at 300 words per page).
