# How Can Air Be Used Doing Work?

Simple water pumps of one sort or another were used before the time of Christ. But air pumps are fairly recent inventions. It was not known until the middle of the seventeenth century that air could be pumped. It would not have become known so soon as that if Otto von Guericke, a German scientist, had not liked to work with science in his spare time. Guericke, mayor of Magdeburg, Germany, experimented with air pressure during his leisure time. As a result of these activities, he invented the first air pump, or “suction pump.” With this pump he demonstrated the force of the atmospheric pressure before the emperor and his “diet” (legislature).

Guericke first made a hollow copper globe, two feet in diameter. He made the two halves of the globe fit together closely enough to be airtight. He did not bolt together or join these halves, or hemispheres, in any way. To this globe he fitted one end of a tube which was made so that it could be opened or closed. He attached the other end of this tube to his air pump. Everything was now ready for the demonstration.

First the tube was opened, and the air was pumped from the globe. The tube was then closed so that air could not enter it. A team of horses was hitched to each hemisphere to try to pull the two halves apart. But the horses could not. Other horses were added to each side. Finally, when there were eight horses on each side, they were able to pull the two halves of the globe apart.

As you can imagine, this demonstration with the Magdeburg hemispheres was viewed with wonder and astonishment by the emperor and his lawmakers. They did not fully understand what held the halves of the globe together.

Even today the correct meaning of the word suction is not generally understood. Many people believe that suction is something that a vacuum does. They think suction means that a vacuum is pulling on something. This idea that suction is drawing or pulling is not correct. Suction is just the opposite. Suction is never a pull but always a push.

Whenever air is pumped out of a space, a partial vacuum is formed in the space.

There can never be a complete, or perfect, vacuum, because it is not possible to pump all the air out of any space. A perfect vacuum would have no air pressure whatever. A partial vacuum has some air pressure, but not so much as that of the atmosphere outside the space. Hence ordinary air pressure always pushes things toward a partial vacuum.