Above all the men of the Renaissance took it on themselves to edit and translate and publish the ancient classics of science and make them available for the study of their own and subsequent generations. The debt which the modern world owes to the Renaissance in this matter is only coming to be properly realized as a consequence of our own development of scholarship in this generation. Only the profound scholar is likely to appreciate properly how much we are indebted to the patient, time-taking work of this period in making books available. Not only the ancient classics but also the works of the Middle Ages on scientific subjects were all published. The early Christian scholars, the Arabians, and above all, the great teachers of the later Middle Ages were edited and printed as an enduring heritage for mankind.
The index of the feeling of the time toward physical science as well as the interest of the scholars of the period in nearly every phase of it is illustrated by the life of Cardinal Nicholas of Cusa, who is usually known as Cusanus. He was a distinguished German churchman who was made Bishop of Brixen and afterwards Cardinal and who had the confidence of the Popes to such a degree that he was sent out as Legate for the correction of abuses in Germany. He was particularly interested in mathematics and the great German historian of mathematics. Cantor, devotes a score of pages to the advances in mathematics which we owe to Cusanus. According to tradition during his journeys over the rough roads in the rude carriage of the time, he studied the curve described through the air by a fly as it was carried round the wheel after alighting on the top of it. He recognized this as a particular kind of curve which we know now as the cycloid and he studied many of its peculiarities and suggested its mathematical import.
He was particularly interested in astronomy and declared that the earth was round, was not the centre of the universe and that it could not be absolutely at rest. As he put it in Latin: terra igitur, quae centrum esse nequit, motu omni carere non potest. He described very clearly how the earth moved around its own axis, and then he added what cannot but seem a surprising declaration for those who in our time think such an idea of much later origin, that he considered that the earth itself cannot be fixed, but moves as do the other stars in the heavens, Consideravi quod terra ista non potest esse fixa sed movetur ut aliae stellae. More surprising still, he even seems to have reached by anticipation some idea of the constitution of the sun. He said: "To a spectator on the surface of the sun the splendor which appears to us would be invisible since it contains as it were an earth for its central mass with a circumferential envelope of light and heat and between the two an atmosphere of water and clouds and of ambient air."
These expressions occur mainly in a book "De Docta Ignorantia," in which the Cardinal points out how many things which even educated people think they know are quite wrong. His other books are on mathematics, though there is a little treatise on the correction of the calendar which shows how thoroughly the men of the time recognized the error that had crept into the year and how capable they were of making the correction. In a book of his on "Static Experiments" he has a very original discussion of laboratory methods for the study of disease which is eminently scientific, and which is described in the chapter on Medicine.
The life of George von Peuerbach, also Puerbach and Purbachius, the Austrian astronomer, one of Cardinal Nicholas' proteges who lived to be scarcely forty and whose greatest work was done just at the beginning of Columbus' Century, is an excellent index of the scientific spirit of the time. About 1440, when he was not yet twenty years of age, he received the degree of Master of Philosophy and of the Liberal Arts with the highest honors at the University of Vienna. After this he seemed to have spent some time at postgraduate work in Vienna, especially in mathematics under Johann von Gmünden. Just about the beginning of Columbus' Century he went to [{346}] Italy. Cardinal Nicholas of Cusa became interested in him and secured him a lectureship on Astronomy at the University of Ferrara. During the next few years he refused offers of professorships, at Bologna and Padua, because he wanted to go back to Vienna to teach in his alma mater. There, with the true Renaissance spirit of non-specialism, he lectured on philology and classical literature, giving special postgraduate courses in mathematics and astronomy. It was at this time that Johann Müller, Regiomontanus, as he is known, came under his tutelage. Purbach deserves the name that has been given him of the father of mathematical astronomy in modern times.
He introduced the decimal system to replace the cumbersome duodecimal method of calculation, which up to his time had been used in mathematical astronomy. He took up the translation of Ptolemy's "Almagest," replaced chords by sines and calculated tables of sines for every minute of arc for a radius of 600,000 units. This wonderful work of simplification naturally attracted wide attention. Cardinal Bessarion was brought in touch with him during a visit to Vienna and was impressed with his genius as an observer and a teacher. He suggested that the work on Ptolemy should not be done on the faulty Latin translation which was the only one available in Vienna at the moment, but on some of the Greek manuscripts of the great Alexandrian astronomer. He offered to secure them and also to provide for Purbach's support during the stay in Rome necessary for the study. The invitation was accepted on condition that his pupil Regiomontanus should go with him. Unfortunately, however, Purbach died before his journey to Rome. His works were very popular in his own time and his commentary on the "Almagest of Ptolemy" as completed by Regiomontanus became one of the standard text-books of the time. Altogether there are some twenty of his works extant and his "New Theory of the Planets" remained a favorite book of reference for astronomers even long after the publication of Copernicus. His industry must have been enormous but was after all not different from that of many of his contemporaries.
Astronomy was to be the great stimulating physical science of the early part of Columbus' Century and Purbach's successor [{347}] in the chain of scientific genius at this time was his pupil Johann Müller, or as he has come to be known from the Latinization of the name of the place of his birth, Königsberg (in Franconia, not far from Munich), Regiomontanus. As we have said, young Müller made his studies with Purbach at Vienna, became very much interested in astronomy and mathematics, at his master's suggestion accompanied Cardinal Bessarion to Italy and under his patronage took up the work of providing an abridgment of Ptolemy's great work, the "Almagest," in a Latin translation for those who might be deterred from the Greek.
Cardinal Bessarion became very much interested in him and gave him a chance to study in Italy. Müller chose Padua and spent nearly ten years there. Whenever anybody in almost any country in Europe wanted to secure opportunities for study beyond those afforded by his native land at this time he went down to Padua. Linacre, Vesalius, John Caius went there for medicine, Copernicus, a little later than Regiomontanus, for mathematics and astronomy and it was the ardently desired goal of many a student's wishes. Müller spent nearly ten years in Italy, most of it at Padua and at the age of about thirty-five returned to Germany to take up his life work. He settled down in Nuremberg, where in connection with Bernard Walther he secured the erection of an observatory. Nuremberg, because of its fine work in the metals, was the best place to obtain mechanical contrivances of all kinds, and many of these were used for the first time for scientific purposes at this observatory. It became quite a show place for visitors and while Nuremberg was developing the literary and artistic circles in which the Pirkheimers, Albrecht Dürer and the Vischers and Adam Kraft shone conspicuously, scientific interest in the city was at a similar high level.
Müller made a series of observations of great value in the astronomy of the time and substituted Venus for the moon as a connecting link between observations of the sun, the stars and the earth. He recognized the influence of refraction in altering the apparent places of the stars and he introduced the use of the tangent in mathematics. His most important work for the time, however, was the publication of a series of astronomical [{348}] leaflets, "Ephemerides Astronomicae" in which his observations were published and also a series of calendars for popular information. These announced the eclipses, solar and lunar, for years before their recurrence and gave a high standing to astronomy as a science. Some of these leaflets even reached Spain and Portugal and encouraged Spanish and Portuguese navigators with the thought that they could depend on observations of the stars for their guidance at sea. In a way, then, Regiomontanus' work prepared the path along which Columbus' discovery was made.