Institute and Museum of History of Science, Florence, ITALY

                      The main characters                   
Pierre Gassendi (1592-1655) Otto von Guericke (1602-1686) Thomas Hobbes (1588-1679)

Otto von Guericke
Otto von Guericke, Experimenta Nova (ut vocantur) Magdeburgica De Vacuo Spatio, Amsterdam 1672

Otto von Guericke, Experimenta Nova (ut vocantur) Magdeburgica De Vacuo Spatio, Amsterdam 1672, frontispiece

The descendent of a well-off family in Magdeburg, he studied Law at the university of Lipsia (1617-1620), Helmstedt (1620) and Jena (1621-1622), then going to Leida, where in addition to his legal studies, he went to course of mathematics and started to deal with engineering problems. After holding various public posts in his home town, he moved in 1631 to Erfurt, to work as an engineer for the Swedish government, transferring then to the service of the Elector of Saxony in 1635. In the years between 1646 and 1676, he held the post of Burgomaster of Magdeburg. Despite the fact that his time was largely filled by the burdens of public life, von Guericke continued to interest himself in experimental science, and was soon aware of the new developments in the debate in physics related to the innovative cartesian theories, and to the barometric experiments of Torricelli. To put Descartes' "plenist" thesis, which denied the existence of the vacuum, to the test, von Guericke thought up and constructed - alongside many failures - various models of pumps to produce a vacuum. In the same years, he replicated the barometric experiments and profoundly studied the problem of air pressure.

It is in this context that, in 1657, Von Guericke performed his most famous experiment. Two bronze hemispheres, around 50 cm in diameter, and fitting together perfectly, were put together, and then, with an air-pump, a vacuum was produced between them. Incredibly, to separate the two parts took the combined forces of two teams of 8 horses, pulling in opposite directions. The evocative experiment, first described in Gaspar Schott's Mechanica hydraulico-pneumatica (1657), and then spectacularly repeated before the Berlin court in 1663, confirmed the torricellian discoveries and highlighted the surprising effects of atmospheric pressure.





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