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Common Science 



FIG. 7. The experiment with the Magdeburg hemispheres. 



Before you pumped the air out of the hemisphere, the 

 compressed air inside of them (you remember all the air 

 down here is compressed) was pushing them apart just 

 as hard as the air outside of them was pushing them 

 together. When you pumped the air out, however, there 

 was hardly any air left inside of them to push outward. 

 So the strong pressure of the outside air against the hemi- 

 spheres had nothing to oppose it. It therefore pressed 

 them very tightly together and held them that way. 



This experiment was first tried by a man living in 

 Magdeburg, Germany. The first set of hemispheres he 

 used proved too weak, and when the air in them was 

 partly pumped out, the pressure of the outside air 

 crushed them like an egg shell. The second set was 

 over a foot in diameter and much stronger. After he 



