Lesson 3: Astronomy after Copernicus
This chapter covers developments in astronomy in the century after Copernicus, including the introduction of the telescope.
Introduction
The story of astronomy in the decades immediately following Copernicus is not that of the triumph of Copernicanism. Astronomers had many other questions in mind besides whether the sun went around the earth or the other way around.
Astronomy in early modern Europe was a practical discipline. Astronomers were caught between two practical applications of their discipline, one of which was declining in importance while the other was rising. The one that was declining was astrology.
Johannes Kepler, the last important astronomer to be a practicing astrologer, is credited with the saying that mother astronomy would starve were it not for the earnings of daughter astrology. (Opposition to astrology was usually religious rather than scientific.)
Ptolemy, the ancient astronomer, was also revered as an astrologer. Astrology was particularly important for astronomers who worked in royal courts. Serious astronomy could not be done without being well financed. It was necessary to buy and maintain good quality instruments, even before the telescope came into astronomical use.
The people who could best finance astronomy were Europe’s kings, queens and rulers. Astrologers were common at royal courts–one of the most famous was the astronomer of Queen Elizabeth of England, Dr. John Dee, who was also a mathematician and claimed to communicate with angels.
Court astrologer/astronomers drew up horoscopes based on the positions of the planets at the time of great events, such as the birth of a prince, the founding of new palace, or the announcement of a new royal policy, and suggested the most propitious times for royal initiatives.
Astrology in the classical tradition was far more complex than the kind of astrology that most people are familiar with today, the kind found in a newspaper horoscope column. It required serious astronomical knowledge. It was also based on a Ptolemaic, earth-centered cosmology.
Astrology, like other forms of magic, declined in importance in the seventeenth century. What dramatically rose in importance was the use of the stars for navigation. As European ships traveled in uncharted and unknown waters far from the sight of land, the question of a ship’s exact position and its distance from the land was urgent and sometimes even life-or-death.
As new territories were discovered, conquered, and settled, rulers wanted to map them as exactly as possible, and, with the rise of centralized royal absolutist monarchies, Europe itself was far more carefully mapped then it had ever been before.
The stars and planets provided the indispensable reference points for these endeavours. But if points on the earth were to be known with exactitude, the stars themselves had to be known with exactitude, as did the paths of the planets through the heavens. Navigators and cartographers used astronomy to organize space. A third practical use for astronomy was to organize time. The effort of calendar reform, which in its early stages had involved Copernicus himself, culminated in the “Gregorian” reform of the calendar announced in 1582.
The result of years of work by astronomers and mathematicians working under the authority of Pope Gregory XIII, the reform created the calendar we use today. Although the astronomers who created the calendar were Ptolemaicists to a man, that made no difference to their work.
