Kepler on supernova, theology and astrology
Posted by Darin Hayton on 12/31 at 12:17 PM
Martin Kemp has written a nice little piece for Nature looking at Kepler’s De stella nova (1604).1 The article’s subtitle indicates the general point Kemp is going to make:
Kepler’s interpretation of the supernova of 1604, De Stella Nova, interwove the science of astronomy with astrology and theology in an attempt to determine the correct birthdate of Jesus.
Like many scholars in early-modern Europe, Kepler enlisted astronomy in his efforts to determine more precisely various aspects of Biblical chronology. Along with Kepler Joseph Scaliger, Isaac Newton, Pierre d’Ailly, Philip Melanchthon and James Ussher all used astronomical events in their efforts to understand Biblical chronology.2 The two most important events in the Biblical account were the creation of the earth and the birth of Jesus. A rich tradition arose around efforts to determine the moment of creation. These efforts frequently relied on the construction of a horoscope for the moment of creation, called Thema mundi. Using the chronology provided in the Bible, scholars worked back from contemporary astrologically significant events (most commonly, conjunctions between the superior planets Jupiter and Saturn) to determine the astrologically important event that accompanied the moment of creation. In other words, they used the Bible as a guide to turn the celestial clock backwards until they arrived at the moment of creation. The German astrologer and imperial secretary to Emperor Maximilian I Joseph Grünpeck concluded that the celestial rebirth each year, when the sun entered Aries, mimicked the moment of creation. Therefore, the sun must have been at the first degree of Aries when God began the process of creating the heavens and the earth. By the time God created the earth, the sun had progressed to 19° of Aries. Grünpeck dutifully drew up a horoscope for this moment:3.⇑
Grünpeck used this information to explain the advent and spread of the morbus gallicus (which scholars today often equate with syphilis). He further used astrology to explain the disease’s symptoms (but that’s the subject of another post)
Kepler focused on the other significant Biblical event: Jesus’s birth. The appearance of a new star in 1604 along with an important planetary conjunction provided him with the opportunity to try his hand at Biblical chronology.
In 1604 Kepler anticipated the next Jupiter-Saturn conjunction. The two planets conjoin approximately every 20 years, slowly working their way through the zodiac. Every 240 years this planetary conjunction would shift from one triplicity—a trio of zodiacal signs that were associated with one of the four elements (earth: Taurus, Virgo, Capricorn; water: Cancer, Scorpio, Piscen; air: Gemini, Libra, Aquarius; fire: Aries, Leo, Sagitarius). Then, every 960 years, Jupiter and Saturn would come together once again in the original triplicity. These conjunctions were labelled according to their frequency: great, greater, and greatest conjunctions, respectively. As the name implies, the more infrequent the conjunction, the more significant its effects. The conjunction in 1604 was a greater conjunction as Jupiter and Saturn shifted into the fiery triplicity. Kepler and other astrologers were, understandably, anxious to see what this latest conjunction would cause.
Then, on 17 October 1604 Kepler noticed a new star in the foot of the constellation the Serpent Bearer. This must be a prodigious event, one pregnant with significance. Two years later, Kepler published his On the New Star in the Foot of the Ophiuchus and on the Fiery Trigon that Began Anew at its Rising. A Booklet Full of Astronomical, Physical, Metaphysical, Meteorological and Astrological Disputations (often referred to by its short Latin title De stella nova)
Kepler argued that this new star was analogous to the star that the Magi had followed—both had occurred during related planetary conjunctions. Using this logic, Kepler had only to look for a greater conjunction that occurred around the birth of Christ. He pointed to the Jupiter-Saturn conjunction in the fiery triplicity during 7-5 BC. The Star of Bethlehem then appeared during this conjunction, leading the Magi to the infant Jesus.
Martin Kemp emphasizes correctly that Kepler was using the sophisticated science of his day to understand Biblical events. For Kepler, whatever the divisions between astronomy, astrology, theology, and chronology (that is, between our conceptions of science and non-science) were, these various activities were complementary. Not antithetical.
Kepler’s work on optics needs to be read in the same way, as part of his broader scientific efforts and quite likely as much motivated by his work in astrology as by his work in astronomy.4 Kepler tried to cleanse astrology of the post-classical accretions that had degraded the discipline. Famously, he wrote a treatise outlining what he considered a more scientific basis for astrology: De fundamentis astrologiae certioribus (Prague, 1602). Kepler wasn’t the only person to see an important connection between optics and astrology. At the beginning of the sixteenth century, the astrologer and imperial physician and mathematician Georg Tannstetter produced an edition of Witelo’s optics because it was useful for his astrology. His colleague and friend Andreas Stiborius produced an edition of Robert Grosseteste’s tract on optics, the Libellus Linconiensis de Phisicis lineis, angulis et figuris, per quas omnes acciones naturales complentur, again because it was useful for astrologers. Later in the century the English mathematician and interviewer of angels John Dee also pointed out the importance of understanding optics for the practicing astrologer. As we realize the breadth of their intellectual activities these scholars become increasingly interesting.
1Martin Kemp, “Johannes Kepler on Christmas,” Nature 462(24 December 2009): 987. The full text of the article is, unfortunately, behind a paywall: link to article.⇑
2On James Ussher, see the post at Renaissance Mathematicus defending Ussher from anachronistic attacks: “In defence of the indefensible.”⇑
3In fact, Grünpeck didn’t calculate anything except the price of Pierre d’Ailly’s book, Concordantia astronomie cum theologia, from which he copied both the logic and the horoscope.⇑
4The Renaissance Mathematicus has a nice post on Kepler’s optics: “Shedding some light!”.⇑