Astronomy in the days of Copernicus - scientists, publications, universities
The astronomical interests of Copernicus developed in the period of significant progress in European astronomy, which took place in the latter part of the 15th century. A considerable contribution in this field of science was made by Georg Peurbach and Johannes Mller, also known as Regiomontanus. Peurbach, in accordance with his own plan to revive astronomy through the study of works by ancient authors, presented in his Theoricae novae planetarum (New Theories of the Planets published in about 1474), a shortened lecture on Ptolemys astronomy and its Arabic critics. He also began to write an in-depth analysis entitled Epitomeof Ptolemys Almagest which after his death was completed by Regiomontanus: the work eventually appeared in 1496. In 1471 Regiomontanus started to operate in Nuremberg where he cooperated with Bernard Walther who realised one of the most interesting observational programmes of that era. The results of the calculations of Mercurys positions made by Walther were used by Copernicus in his De revolutionibus.
Having begun his university studies in the capital of Poland in 1491, Copernicus had the opportunity to come into contact with the Cracow school of astronomy, flourishing at that time. In the well-known chronicle of the world, published by Hartmann Schedel in 1493, one may find a statement that in the Cracow university studies of astronomy have reached the highest level and many claim that there is no greater one in the whole of Germany. In that period foreign students did indeed come to Cracow, many of whom later became professors of astronomy in universities in Heidelberg, Vienna, or Wittenberg. At the Academy of Cracow, lectures were based on textbooks which were very popular in medieval Europe. In the case of astrology, Tetrabiblos by Claudius Ptolemaeus and Latin translations of Arabic writings were used. Astronomy was taught according to the Tractatus de sphaera by John of , or Johannes de Sacrobosco, Theorica planetarum by Gerard of Sabionetta, later replaced by Theoricae novae planetarum by Georg Peurbach, and commentaries on the Alfonsine Tables. The scientific activities of astronomers from Cracow concentrated on explaining basic treatises and astronomical tables, and their duties included the preparation of ephemerides which would give warning of interesting astronomical phenomena, calendars, and astrological predictions. The most outstanding representatives of the Cracow school of astronomy were: Marcin Król of Żurawica, Marcin Bylica of Olkusz, Jan of Głogów and his student Wojciech of Brudzewo.
One of the most important features of that scientific community was a critical attitude towards the state of European astronomy, which was based on better or worse developed versions of Ptolemys models and the cosmology of celestial spheres. Marcin Bylica, for example, contributed to the work by Regiomontanus entitled Disputationes inter Viennensem et Cracoviensem super Cremonensis in Planetarum theoricas deliramenta in 1464, though he did not write any significant astronomical treaty himself. As the title says, this dispute between the representatives of the astronomical schools of Cracow and Vienna concerned Theorica planetarum, which was then used, and pointed out the weaknesses of this work. And Wojciech of Brudzewos commentary to Theoricae novae planetarum, which was written in 1482 and published in Milan thirteen years later, devoted much attention to the critical opinions of earlier astronomers on eccentric circles and epicycles, as well as on equant. What is worth mentioning is the fact that at the end of the fifteenth century in the community of Cracow scientists, all the most important trends of European natural philosophy were known and commented on.
In Italy, where he continued his studies, Copernicus had the opportunity to conduct observations together with Domenico Maria Novara, an astronomy professor from Bologna; some of the results that they had obtained were used by Copernicus while working on the heliocentric system. Thanks to Georg Joachim Rheticuss account, we now know that in 1500 in Rome Copernicus delivered a lecture devoted to mathematics which in all probability meant astronomy, but its subject still remains unknown.
Having returned to Warmia, Copernicus maintained contact with European astronomy. This is testified, among other things, by Romes request for his opinion on the calendar reform that was discussed during the 5th Lateran Council (1512-1517), as well as a critique of a dissertation on the movement of the eighth sphere by John Werner published in 1522 in Nuremberg. Copernicuss observations of eclipses conducted together with other scholars, carried out simultaneously by him in Warmia and his colleagues in Cracow, as well as a letter from Cardinal Schoenberg from Rome in 1536 in which the latter offered Copernicus assistance in the publication of his work, may also be another proof of his ongoing cooperation with European astronomers. Another important piece of evidence that the author of De revolutionibus maintained contacts with European astronomers was an expedition of Rheticus, sent to Frombork by the community of scholars from Nuremberg in 1539.
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