Astronomy in Rudolfine Prague

Thanks to Rudolf II, a remarkable and unparalleled meeting of the minds took place in Prague at the end of the European Renaissance. The seat of his power was Prague Castle, at the centre of Bohemia, at the geographical centre of Europe, at the centre of the known world. Here he established a magic circle into which he invited some of the most creative and original minds of the day. But it wasn’t political power he was after, he was already the most powerful man in Christendom, he was after power through knowledge, in both its positive and negative aspects. Rudolf had a love of learning, passion for the arts, interest in natural sciences and delight in collecting.

Portrait of Rudolf II, Holy Roman Emperor c. 1580
Portrait of Rudolf II, Holy Roman Emperor c. 1580

Described by a noted contemporary as “the greatest art patron in the world”, Rudolf II Habsburg (1552–1612), king of Hungary and Bohemia, and Holy Roman Emperor, raised court patronage in post-Renaissance Europe to a new level of breadth and extravagance. The thriving city and era over which he reigned, from 1583 until his death twenty-nine years later, is known as Rudolfine Prague. Seat of the emperor almost uninterruptedly from the mid 14th century, Prague became, under Rudolf’s guidance, one of the leading centers of the arts and sciences on the continent. His taste for outstanding decoration and fantastic imagery were legendary, while his ambition and insight as a patron and collector changed the way art would be viewed by future generations.

Prague was founded in the late 9th century around the castle district of Hradcany, the oldest of the city’s four districts, and became the imperial residence during the reign of Charles IV in the 1300s. Rudolf II, son of Maximilian II, was named Holy Roman Emperor in 1576, and returned the court to Prague in 1583, after its temporary relocation to Vienna. As the city once again became the political and cultural focus of the empire and Hradcany earned the status of a royal town, Rudolf II brought into his service some of the most important European artists, architects, scientists, philosophers, and humanists, the English magus John Dee, the German alchemist Oswald Croll, the Polish alchemist Michael Sendivogius, the Italian philosopher Giordano Bruno, turning Prague into what has been referred to as a “Parnassus of the arts”.

Prague Castle in 1595
Prague Castle in 1595

The emperor’s ambitions as an architectural patron are evidenced by his redesign and expansion of the castle, the construction of a new town hall and archbishop’s palace, and the commissioning of several new churches. Yet, it was in painting, sculpture, and the decorative arts that Rudolf’s impact was most celebrated and distinct. Among the artists who came to the imperial court were the painters Bartholomeus Spranger, Hans von Aachen, Pieter Stevens, and Roelandt Savery; the miniaturists Joris Hoefnagel and his son Jacob Hoefnagel; the sculptor Adriaen de Vries; the goldsmiths Paulus van Vianen and Wenzel Jamnitzer; and Aegidius Sadeler, who, as Imperial Printmaker (from 1597), popularized the emperor’s image and disseminated knowledge of his artists’ works. Foreign artists were especially prized by Rudolf because they gave international weight to his domain and satisfied his taste in art—for Italian and Netherlandish work, in particular, fostered at the Habsburg court in Spain, where he was educated.

Rudolf’s unrivaled passion for collecting culminated in one of the greatest of princely Kunstkammers, which contained small bronzes, works in cut stone, medallions and ivories, books and drawings, coins, scientific instruments and natural objects, as well as some paintings. Often dismissed as an unsystematic cabinet of curiosities intended for amusement or wonder, Rudolf’s Kunstkammer probably served as a place of refuge or serious contemplation, and indeed reflected, in an ordered way, the broader scientific and artistic interests of the court. Gerhard Emmoser’s dazzling celestial globe with clockwork; Female Nude; Apollo; Relief Allegory of Virtues and Vices at the Court of Emperor Charles V, listed in the early seventeenth-century inventory of the collection, exemplify this close association. The intricate and colorful allegorical portraits of Rudolf II painted by Giuseppe Arcimboldo point to the direct collaboration that took place between artists and scholars. Rudolf also amassed a collection of paintings numbering in the thousands. Italian works were common, including those by Paolo Veronese (Mars and Venus United by Love), Correggio, and Leonardo da Vinci; as were works by Northern European masters, including Albrecht Dürer and Pieter Bruegel the Elder.

Rudolf painted as Vertumnus, Roman God of the seasons, by Giuseppe Arcimboldo (1590–1). Rudolf greatly appreciated the work.
Rudolf painted as Vertumnus, Roman God of the seasons, by Giuseppe Arcimboldo (1590–1). Rudolf greatly appreciated the work.

In addition to stimulating culture in Prague through enlightened patronage and collecting, Rudolf II offered direct support of the arts, visiting his artists in their workshops and raising the status of the local painters’ guild from the level of a craft to that of a liberal art. Soon after the emperor’s death in 1612, his collections and court entourage were largely dispersed, leaving little in situ. The legacy of Rudolfine Prague, while apparent in some of the surviving buildings and landscaping of the old city, is best appreciated in the works of art commissioned and collected by one of Europe’s most influential and adventurous patrons.

Since he never travelled, he made the world come to him. The astronomers Tycho Brahe was made Imperial Mathematician in 1599, and then Johannes Kepler, who first served as Brahe’s assistant and then succeeded him in 1601.

Tycho Brahe (1546 - 1601)
Tycho Brahe (1546 – 1601)

Tycho Brahe was born into Danish nobility, the oldest son of eleven children. He spent his teens and early adult years attending several universities, similar to the way Copernicus spent the last years of the 15th century. He also had a connection to the University of Wittenberg – he attended classes there for five months in 1566 and studied astronomy under Reinhold’s successor and Melanchthon’s son-in-law (and pro-Copernican), Caspar Peucer. Later in 1566, while studying at the University of Rostock, Brahe fell into an argument with another student that escalated into a duel. In the ensuing sword fight, Brahe’s foe sliced off his nose, and the Dane had to wear a brass nosepiece for the rest of his life.

Early in his schooling, Tycho fell in love with astronomy. He started buying astronomical instruments and books and making observations. On November 11, 1572, Tycho made one of the most significant observations in the history of astronomy. A little after sunset on that day, he noticed an extraordinarily bright star that he knew had not been there the night before. Brahe went on to observe it for the next 16 months, until it was no longer visible in the firmament. It is now known that he observed a supernova, or exploding star. This bright star was seen by all astronomers in Europe, most of whom thought that it was a comet, then believed that the phenomena occurred between the moon and the sun. However, only Brahe took careful enough measurements to know that it was a star, a fixed star.

In 1573, Tycho published a short book, only about fifty pages long, about his discovery. The book and its author quickly became famous. The ambitious Tycho then used his newfound status to persuade the king of Denmark to build him an observatory. The king gave Brahe a small island near Copenhagen, called Hven, and paid for what quickly became the finest astronomical centre in Europe, one filled with the most advanced instruments available. The king also provided enough financial support for Tycho to hire dozens of research assistants. Brahe, already rich through his family, became even wealthier under the king’s patronage. Like nearly all astronomers before him – except for Copernicus – Tycho believed strongly in astrology. He was an active astrologer, producing prognostications and horoscopes for his patrons, including the king of Denmark, for most of his career.

General view of the Observatory of Uraniborg, constructed circa 1584 by Tycho Brahe
General view of the Observatory of Uraniborg, constructed circa 1584 by Tycho Brahe
Tycho Brahe's observatory on the Island of Hven
Tycho Brahe’s observatory on the Island of Hven

Brahe was fascinated with Copernicus. Though he was never won over to the heliocentric model, he nevertheless honored its founder’s memory. He worked diligently to obtain an already rare copy of the Commentariolus (which Brahe is credited for naming, until Brahe it had no formal title). He sent an assistant to Frombork in 1584 in order to gain a better understanding of Copernicus’ observations. The canons on Cathedral Hill gave Tycho Copernicus’ triquetrum, which they had guarded with care for over forty years. Tycho cherished it for the rest of his life, and displayed it in what was essentially a museum on his island.

On November 13, 1577, Brahe added to his fame. That night he saw for the first time a large comet with a long tail. After observing it carefully for about two months, the Dane knew that it was not a sublunar (occurring between the earth and the moon) phenomenon. It was out in space, among the planets, which meant that it must be piercing the planetary spheres. Those who adhered to Ptolemy’s model believed that the planets were attached to physical, tangible spheres – that is, spherical shells. Here was proof that there were no shells. The 1572 supernova showed that the heavens were changeable, and the comet proved that the planets did not ride on celestial spheres. What else about the old model was not valid?

15 year old King Christian IV with Tycho Brahe at Uraniborg in 1592. Brahe left the observatory on Hven 5 years later, due to a heavy dispute between the King and him.
15 year old King Christian IV with Tycho Brahe at Uraniborg in 1592. Brahe left the observatory on Hven 5 years later, due to a heavy dispute between the King and him.

Frederick II, Tycho’s patron, died in 1588. The new king, Christian IV, was less committed to the astronomer’s research program, which was quite expensive to maintain. Over the next decade, Brahe slowly fell out of favour with the young king and had to close down his observatory. He left his island in 1597 and by 1599 he settled in Prague to become Rudolf’s court astronomer and close companion. By this stage, Brahe’s glory days were behind him. He made one more major discover, though – Johannes Kepler, who became his research assistant in early 1600.

Tycho Brahe demonstrating a celestial globe to Emperor Rudolph II, a painting by Eduard Ender, 1855
Tycho Brahe demonstrating a celestial globe to Emperor Rudolph II, a painting by Eduard Ender, 1855
Johannes Kepler (1571 - 1630)
Johannes Kepler (1571 – 1630)

Johannes Kepler was a prodigy. His teachers recognised his impressive mathematical abilities early in his schooling. At the age of 20, he received his master’s degree from the University of Tübingen, where he studied under Michael Maestlin, who was an early (though stealth) Copernican.

When I was studying under the distinguished Michael Maestlin at Tübingen six years, seeing the many inconveniences of the commonly accepted theory of the universe, I became so delighted with Copernicus, whom Maestlin often mentioned in his lectures, what I often defended his opinions in the students’ debates about physics… I have by degrees – partly out of hearing Maestlin, partly by myself – collected all the advantages that Copernicus has over Ptolemy.

This passage appeared in his important book, the first of many for the prolific Kepler, entitled The Cosmic Mystery (Mysterium cosmographicum). In its pages, Kepler presented his model of the universe, which was decidedly Copernican. He also argued forcefully for the sun being the reason for this configuration. Copernicus placed the sun at the centre of the universe but did not give it an active role in the scheme – Kepler did, thus anticipating Newton and the theory of universal gravity.

Kepler’s Cosmic Mystery was published in Tübingen, where the professors at the university and his publisher had asked him to make part of his book understandable to laymen. So Kepler wrote a very accessible introduction to his work that directly addressed why Copernicus’ system was dramatically better than Ptolemy’s. The book was published in 1596, 53 years after On the Revolutions. From then on, the tide turned towards Copernicus’ model of the heavens. Kepler sent copies of the book to Galileo (whom he had never met) and Tycho (whom he had also never met). Although the book contained several fundamental flaws, they were not discovered until later. The work had a powerful influence. A leading scholar of early astronomy once noted: “Although the principal idea of the Cosmic Mystery was erroneous, Kepler established himself as the first… scientist to demand a physical explanation for celestial phenomena. Seldom in history has so wrong a book been so seminal in directing the future course of science.”

With the Counter-Reformation gathering steam, the staunchly Lutheran Kepler and his family felt the need to leave Catholic Graz in 1599. He made a bold move to go directly to the most famous astronomer in Europe – Tycho Brahe who was now at Rudolf’s court. With the approval of Rudolf, Kepler became Brahe’s assistant in early 1600.

When they first met, Brahe was fifty-four and Kepler was twenty-nine. It was not an easy collaboration. Kepler called his master ‘the phoenix among astronomers’ but Brahe soon began to treat him like a servant. Where Brahe was an elegant, extravagant aristocrat who believed that the Sun orbited the Earth, Kepler was an impoverished, introverted teacher who believed the Earth orbited the Sun. It was not long before they had a row which led Kepler to withdraw from Benátky Castle. But it was only temporary: the pull of making a great impact in science was stronger than personal differences. Yet for all their differences and tensions, their respective skills proved a perfect match. Brahe was probably the best observational astronomer of all time, whereas Kepler, with poor eyesight, had mathematical abilities second to none. Brahe was able to measure the movements of the planets while Kepler was able to formulate their laws. By bringing the two men together, Rudolf inadvertently made a huge contribution to astronomy in particular and to science in general.

In 1601, Brahe fell terminally ill. Only 56 years old and with mountains of work to finish, the Dane beseeched Kepler to continue the important work on his astronomical tables. It was a scene that harkened back to Peurbach urging Regiomontanus to continue with the Epitome, Copernicus trusting Rheticus with his life’s work when he left Frombork, and Rheticus charging Otto to complete his trigonometry volume. Brahe called his tables the Rudolfine Tables after Rudolf II. Brahe expected Kepler to make the tables fit with his geoheliocentric theory, but it didn’t work out that way.

In this depiction of the Tychonic system, the objects on blue orbits (the Moon and the Sun) revolve around the Earth. The objects on orange orbits (Mercury, Venus, Mars, Jupiter, and Saturn) revolve around the Sun. Around all is a sphere of fixed stars.
In this depiction of the Tychonic system, the objects on blue orbits (the Moon and the Sun) revolve around the Earth. The objects on orange orbits (Mercury, Venus, Mars, Jupiter, and Saturn) revolve around the Sun. Around all is a sphere of fixed stars.

Brahe died, and Rudolf appointed Kepler Imperial Mathematician. Rudolf invited Kepler to take responsibility for Brahe’s instruments and manuscripts and astronomical data. As a result of Rudolf’s perspicuity and generosity, Kepler was able to work in Prague without the fears that Galileo had experienced in Padua and Florence. He was to stay in Prague for twelve years until Rudolf’s death. During this time he wrote about thirty treatises, including his 1609 masterpiece Astronomia nova.

Johannes Kepler and Rudolf II in Prague
Johannes Kepler and Rudolf II in Prague

Kepler was troubled by certain discrepancies in the orbits of the planets. He knew that they could not be ascribed to measurement errors because he was aware of just how accurate Brahe’s measurements were. Though there was only an eight minutes of an arc inconsistency with perfect circular orbits, those eight minutes could not be ignored. There had to be some way to explain it. By 1605, after great effort, Kepler devised the idea that carved his crucial place in the history of science – the ellipse: “With reasoning I derived from the physical principles agreeing with experience, there is no figure left for the orbit of the planet except a perfect ellipse.” His first book based on this profound insight was Astronomia nova, published in 1609. As the title implies, the book laid the foundations of the new astronomy.

After 1612, Kepler moved often for professional and religious reasons, yet he still found time to write the definitive technical book that took Copernicus’ fundamental insights in On the Revolutions and redid them using his own discovery of elliptical orbits. The book was entitled Epitome astronomiae Copernicanae and it appeared in three volumes from 1617 to 1621. Kepler’s Epitome was a treasure and it was later utilised by Isaac Newton.

Active and constantly writing to the end, Kepler died of a fever at the age of 59 in 1630. He had finally finished Brahe’s tables and had them published in 1627.

Johannes Kepler firmly established the fundamental truth of Copernicus’ heliocentric model among astronomers and mathematicians. But Kepler’s published works, like Copernicus’, were unrelentingly technical. The scholar who established the Copernican view among laypeople was his contemporary Galileo.

Galileo Galilei (1564 – 1642)
Galileo Galilei (1564 – 1642)

Galileo Galilei was born seven years before Kepler. The native of Pisa was the oldest of seven children born to a well-to-do family; his father was a noted musician and music theorist. Galileo was first attracted to mathematics and became a professor of mathematics at the University of Pisa in 1589, at the age of twenty-five. In addition to mathematics, he was also fascinated by basic physics. He appeared to be indifferent about astronomy, but when Kepler sent him a copy of his Cosmic Mystery, Galileo’s letter of thanks revealed a deep interest:

Many years ago I accepted Copernicus’ theory, and from that point of view I discovered the reasons for numerous natural phenomena, which unquestionably cannot be explained by the conventional cosmology. I have written down many arguments as well as refutations of objections. These however, I have not dared to publish up to now. For I am thoroughly frightened by what happened to our master, Copernicus. Although he won immortal fame among some persons, nevertheless among countless (for so large is the number of fools) he became a target of ridicule and derision. I would of course have the courage to make my thoughts public, if there were more people like you. But since there aren’t, I shall avoid this kind of activity.

Although Galileo says in his letter that he wants to avoid public ridicule, he later showed great bravery in the name of the truth that he believed in.

More about Galileo in a previous post we wrote about him, The Father of Modern Science

It was 400 years ago this month that On the Revolutions was officially outlawed by the Church, by being placed on the Index of Forbidden Books by the Congregation of the Index. Seventeen years later, in 1633, Galileo was found guilty by the Inquisition for voicing the Copernican worldview, which had been officially outlawed in 1616. Aging, ailing and threatened with torture by the Inquisition, Galileo recanted his Copernican views and his discoveries on April 30, 1633.

Pope Urban VIII found several passages in The Dialogue Concerning the Two Chief World Systems to be direct affronts to positions he held; the pope’s beliefs were endorsed in the book by the buffoonish character called Simplicio 🙂 Possibly not as subtle a message as Galileo had hoped.

Though the sentence was not onerous (house arrest for the rest of his days) and he was able to do practically anything he wanted, the effect was severe. Being forced to recant his own scientific findings as “abjured, cursed and detested” caused him great personal anguish but saved him from being burned at the stake. Galileo was never the same.

On the Revolutions was easily available throughout its time on the Index, but the ban on openly endorsing the Copernican cosmology was sufficient to accuse Galileo of heresy. Copernicus’ book was not removed from the Index for more than 200 years – the first Index on which On the Revolutions did not appear was published in 1835. It was joined on the Index by Galileo’s book. In 1757, Galileo’s Dialogue Concerning the Two Chief World Systems was removed from the Index. And in 1992, more than 350 years after the Roman Catholic Church condemned Galileo, the Vatican formally and publicly cleared Galileo of any wrongdoing. On 31 October 1992, Pope John Paul II expressed regret for how the Galileo affair was handled, and officially conceded that the Earth was not stationary! And I thought things were moving slowly at work 🙂

Excerpts from Copernicus’ Secret, by Jack Repcheck and The Mercurial Emperor, by Peter Marshall

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