Otto von Guericke ( , , ; spelled Gericke until 1666; – ) was a German scientist, inventor, mathematician, and physicist. His pioneering scientific work, the development of experimental methods and repeatable demonstrations on the physics of the vacuum, atmospheric pressure, electrostatic repulsion, his advocacy for the reality of "action at a distance" and of "absolute space" were noteworthy contributions for the advancement of the Scientific Revolution.
Biography
Early life and education
Otto von Guericke was born to a patrician family of Magdeburg. He was privately tutored until the age of fifteen. In 1617 he began studying law and philosophy at the Leipzig University.
Political career
thumb|left|[[Sack of Magdeburg, imperial troops have conquered the toll redoubt and enter the suburbs, April 1631]]
Von Guericke was the offspring of one of Magdeburg's leading patrician families, that were well-educated and well-connected. His father and grandfather had been life-long members of the city council and at various occasions during their careers been appointed to serve as mayor of the city. In 1626, Otto von Guericke started his career as political representative of Magdeburg and accepted an official appointment to join the city council. However, in 1618, the Thirty Years' War had broken out. This exceptionally long, tragic and destructive conflict would soon also descend upon Magdeburg. Only a few years later, he had luckily fled from the city before an army of the imperial Catholic League, led by the Count of Tilly had completely surrounded and cut off Magdeburg. The attack culminated in the single most devastating event of the entire war, namely the Sack of Magdeburg. In May 1631, the imperial troops had crushed the city walls and indiscriminately plundered the riches. Around eighty percent of its more than 25,000 inhabitants perished. The material loss was also unusually high as widespread fires destroyed about 1,700 of a total of 1,900 buildings, including all of von Guericke's personal property. He returned to Magdeburg in 1631 and his academic engineer education designated him an appointee of the reconstruction committee.
Diplomatic pursuits
Otto von Guericke's first diplomatic mission on behalf of the city led him in September 1642 to the court of the Elector of Saxony at Dresden. Von Guericke's mandate was to bring about a more lenient treatment from the Saxon military commander for Magdeburg. In 1648, he represented the city at the peace treaty delegation, that ended the Thirty Year's War. During a 1654 diplomatic mission to Regensburg, Guericke presented his invention of the air-pump to impress those he was going to meet and help sway the talks in his favour, as well as promote his own scientific achievements. Diplomacy assignments, often dangerous as well as tedious, would occupy much of his time for the next twenty years. His private life, of which much remains unclear, was developing in parallel. Otto von Guericke utilised both his official status and his scientific knowledge in each other's support to serve his city's political agenda. Demonstrations of his inventions, such as the air-pump and the electrostatic generator were meant to impress his audiences and improve and extend political communication. He would, if necessary forgo scientific and technical elaborations on how his showpieces worked, leaving people to believe in his wizardry, a characteristic that was of great use for the promotion of a great leader. This book came to the attention of Robert Boyle who, stimulated by it, embarked on his own experiments on air pressure and the vacuum, and in 1660 published New Experiments Physico-Mechanical touching the Spring of Air and its Effects. The following year this was translated into Latin and, made aware of it in correspondence with Fr. Schott, von Guericke acquired a copy. In the Preface to the Reader he claims to have finished the book on 14 March 1663, though publication was delayed for another nine years until 1672. In 1664, his work again appeared in print, again through the good offices of Gaspar Schott, the first section of whose book Technica Curiosa, titled Mirabilia Magdeburgica, was dedicated to von Guericke's work. The earliest reference to the celebrated Magdeburg hemispheres experiment is on page 39 of the Technica Curiosa, where Schott notes that von Guericke had mentioned them in a letter of 22 July 1656. Schott goes on to quote a subsequent letter of von Guericke of 4 August 1657, in which he states that he now had carried out the experiment, at considerable cost, with 12 horses.
The 1660s marked the ultimate end for the Magdeburg citizen's hope of achieving Free Imperial City status, a goal to which von Guericke had devoted some twenty years of diplomatic effort. On behalf of Magdeburg, he was the first signatory to the Treaty of Klosterberg in 1666 whereby Magdeburg accepted a garrison of Brandenburg troops (upon the withdrawal of the imperial garrison) and the obligation to pay dues to the Great Elector, Friedrich Wilhelm I of Brandenburg. Despite the Elector's crushing of Magdeburg's political aspirations, the personal relationship of von Guericke and Friedrich Wilhelm remained warm. The Great Elector was a patron of scientific scholarship. He had employed von Guericke's son, Hans Otto, as his resident in Hamburg and in 1666 had called Otto himself to the Brandenburg Rat. When the Experimenta Nova finally appeared it was prefaced with a dedication to Friedrich Wilhelm.
Later years
In 1677 von Guericke was reluctantly permitted to step down from his civic responsibilities, after repeated requests. In January 1681, as a precaution against an outbreak of the plague then threatening Magdeburg, he and his second wife Dorothea moved to Hamburg, where their son Hans Otto lived. There von Guericke died peacefully on 11 May (Julian) 1686, to the day 55 years after he had fled the siege in 1631. His body was returned to Magdeburg for interment in the on 23 May (Julian). The Otto von Guericke University Magdeburg was named in his honour.
Primary publications
There are three bodies of text, that contain systematic treatises on von Guericke's scientific work.
- 1. Friar Gaspar Schott's 1657 work Mechanica Hydraulico-pneumatica, originally intended as a brief guide to the hydraulic and pneumatic instruments in Athanasius Kircher's Roman museum, an appendix added by Schott, is a detailed account of Guericke's experiments on vacuums.
- 2. Friar Gaspar Schott's 1664 Technica Curiosa, with appendix that contains a reupload of the 1657 account plus more recent material from Guericke.
<gallery>
File:Von Guericke-1.jpg|1672 copy of "Experimenta Nova (ut vocantur) Magdeburgica de Vacuo Spatio"
File:Von Guericke-3.jpg|Title page to "Experimenta Nova"
File:Von Guericke-2.jpg|Title page illustration in "Experimenta Nova"
File:Von Guericke-6.jpg|Index to "Experimenta Nova"
</gallery>
Scientific work
Nature of Space and the Possibility of the Void
Book II of the Experimenta Nova is an extended philosophical essay in which von Guericke puts forward a view of the nature of space similar to that later espoused by Newton. He is explicitly critical of the plenist views of Aristotle and of their adoption by his younger contemporary Descartes. A particular and repeated target of his criticism is the manner in which the "nature abhors a vacuum" principle had migrated from simply a matter of experiment to a high principle of physics which could be invoked to explain phenomena such as suction but which itself was above question. In setting out his own view, von Guericke, while acknowledging the influence of previous philosophers such as Lessius (but not Gassendi), makes it clear that he considers his thinking on this topic to be original and new. There is no evidence that von Guericke was aware of the Nouvelles Experiences touchant le vide of Blaise Pascal published in 1647. In the Experimenta Nova, Book III, Ch. 34, he relates how he first became aware of Torricelli's mercury tube experiment from Valerianus Magnus at Regensburg in 1654. Pascal's work built upon reports of the mercury tube experiment which had reached Paris via Marin Mersenne in 1644. An indication of the unresolved status of the "nature abhors a vacuum" principle at that time may be taken from Pascal's opinion, expressed in the conclusion of the Nouvelles Experiences, when he writes: "I hold for true the maxims set out below: (a) that all bodies possess a repugnance to being separated one from another and from admitting a vacuum in the interval between them – that is to say that nature abhors a void." Pascal goes on to claim that this abhorrence of a void is, however, a limited force and thus that the creation of a vacuum is possible.
There were three broad currents of opinion from which von Guericke dissented. Firstly, there was the Aristotelian view that there simply was no void and that everything that exists objectively is in the category of substance. The general plenist position lost credibility in the 17th century, owing primarily to the success of Newtonian mechanics. It was revived again in the 19th century as a theory of an all-pervading aether and again lost plausibility with the success of Special Relativity. Secondly, there was the Augustinian position of an intimate relation between space, time, and matter; all three, according to St. Augustine in the Confessions (Ch. XI) and the City of God (Book XI, Ch. VI), came into being as a unity and ways of speaking that purport to separate them – such as "outside the universe" or "before the beginning of the universe" are, in fact, meaningless. Augustine's way of thinking is also attractive to many and seems to have a strong resonance with General Relativity. The third view, which von Guericke discusses at length, but does not attribute to any individual, is that space is a creation of the human imagination. Thus, it is not truly objective in the sense in which matter is objective. The later theories of Leibniz and Kant seem inspired by this general outlook, but the denial of the objectivity of space has not been scientifically fruitful. His model consisting of a piston and an air gun cylinder with two-way flaps designed to pull air out of whatever vessel it was connected to, and used it to investigate the properties of the vacuum in many experiments. Guericke demonstrated the force of air pressure with dramatic experiments.
In 1657, he machined two 20-inch diameter hemispheres and pumped all the air out of them, locking them together with a vacuum seal. The air pressure outside held the halves together so tightly that sixteen horses, eight harnessed to each side of the globe, could not pull the halves apart. It would have required more than 4,000 pounds of force to separate them. It is estimated that by pumping the air out of these spheres, he was able to reduce the internal pressure to roughly 1/25 of an atmosphere. Von Guericke also showed that electrical (magnetic) attraction does not require a medium to operate in