Magdeburg hemispheres

Otto von Guericke demonstrates the Magdeburg hemispheres in Regensburg, Germany, thus proving the vacuum... 

There is no way that we can model every atom or molecule in a block of material. It is far better to understand the overall macroscopic behavior of a material in terms of the continuum mechanics of elasticity theory, for example. However, it is equally evident that such continuum theories must fail as we approach molecular dimensions where adhesive failure is occurring. It is far too simplistic to suggest that a single variable in the equation of state (e.g. stress or pressure) should dictate adhesion. This might have worked for the Magdeburg hemispheres but does not work for molecular forces. Instead, consider the situation deincted in Fig. 7.14. This shows that, at large scales we should treat... 

The Burgomaster of the city, Otto von Guericke, was then performing the Magdeburg miracles with the evacuated hemispheres which sixteen horses could not separate and with his curious barometer, the little man who remained hidden in a tube when the weather was to be... 

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