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31-08-2015, 08:16

Interpreting Visual Evidence

Astronomical Observations and the Mapping of the Heavens

Ne (often-repeated) ; i narrative about the scientific revolution is !; that it marked a crucial ::::::::::: break separating modern science from an earlier period permeated by an atmosphere of superstition and theological speculation. In fact, medieval scholars tried hard to come up with empirical evidence for beliefs that their faith told them must be true, and without these traditions of observation, scientists like Copernicus would never have been led to propose alternative cosmologies (see "Ptolemaic Astronomical Instruments" on page 521).

The assumption, therefore, that the "new" sciences of the seventeenth century marked an extraordinary rupture with a more ignorant or superstitious past is thus not entirely correct. It would be closer to the truth to suggest that works such as that of Copernicus or Galileo provided a new context for assessing the relationship between observations and knowledge that came from other sources. Printed materials provided opportunities for early modern scientists to learn as much from each other as from more ancient sources.

The illustrations here are from scientific works on astronomy both before and after the appearance of Coperni-

A. The Ptolemaic universe, as depicted in Peter Apian, Cosmographia (1540).

It at the night sky. Galileo studied the moon, finding on it mountains, plains, and other features of an earthlike landscape. His observations suggested that celestial bodies resembled the earth, a view at odds with the conception of the heavens as an unchanging sphere of heavenly perfection, inherently and necessarily different from the earth. He saw moons orbiting Jupiter, evidence that earth was not at the center of all orbits. He saw spots on the sun. Galileo published these results, first in The Starry Messenger (1610) and then in Letters on Sunspots in 1613. The Starry Messenger, with its amazing reports of Jupiter’s moons, was short, aimed to be read by many, and bold. It only hinted at Galileo’s Copernicanism, however. The Letters on Sunspots declared it openly.

C. Brahe's universe (c. 1572, A, earth; B, moon; C, sun).

D. Galileo's sunspots, as observed through a telescope (1612).

Cus's work. All of them were based on some form of observation and claimed to be descriptive of the existing universe. Compare the abstract illustrations of the Ptolemaic (image A) and Copernican (image B) universes with Tycho Brahe's (image C) attempt to reconcile heliocentric observations with geocentric assumptions or with Galileo's illustration of sunspots (image D) observed through a telescope.

Questions for Analysis

1. What do these illustrations tell us about the relationship between knowledge and observation in sixteenth-and seventeenth-century science? What kinds of knowledge were necessary to produce these images?

2.  Are the illustrations A and B intended to be visually accurate, in the sense that they represent what the eye sees?

Can one say the same of D? What makes Galileo's illustration of the sunspots different from the others?

3. Are the assumptions about observation contained in Galileo's drawing of sunspots (D) applicable to other sciences such as biology or chemistry? How so?

A seventeenth-century scientist needed powerful and wealthy patrons. As a professor of mathematics, Galileo chafed at the power of university authorities who were subject to church control. Princely courts offered an inviting alternative. The Medici family of Tuscany, like others, burnished its reputation and bolstered its power by surrounding Itself with intellectuals as well as artists. Per-

Suaded he would be freer at its court than in Padua, Galileo took a position as tutor to the Medicis and flattered and successfully cultivated the family. He addressed The Starry Messenger to them. He named the newly discovered moons of Jupiter “the Medicean stars.” He was rewarded with the title of chief mathematician and philosopher to Cosimo de’ Medici, the grand duke of Tuscany. Now well positioned in Italy’s networks of power and patronage, Galileo was able to pursue his goal of demonstrating that Copernicus’s heliocentric (sun-centered) model of the planetary system was correct.

This pursuit, however, was a high-wire act, for he could not afford to antagonize the Catholic Church. In 1614, however, an ambitious and outspoken Dominican monk denounced Galileo’s ideas as dangerous deviations from biblical teachings. Other philosophers and churchmen began to ask Galileo’s patrons, the Medicis, whether their court mathematician was teaching heresy.

Disturbed by the murmurings against Copernicanism, Galileo penned a series of letters to defend himself, by addressing the relationship between natural philosophy and religion, and he argued that one could be a sincere Copernican and a sincere Catholic (see Analyzing Primary Sources on page 529). The Church, Galileo said, did the sacred work of teaching scripture and saving souls. Accounting for the workings of the physical world was a task better left to natural philosophy, grounded in observation and mathematics. For the Church to take a side in controversies over natural science might compromise the Church’s spiritual authority and credibility. Galileo envisioned natural philosophers and theologians as partners in a search for truth, but with very different roles. In a brilliant rhetorical moment, he quoted Cardinal Baronius in support of his own argument: the purpose of the Bible was to “teach us how to go to heaven, not how heaven goes.” Nevertheless, in 1616, the Church moved against Galileo. The Inquisition ruled that Copernicanism was “foolish and absurd in philosophy and formally heretical.” Copernicus’s De Revolutionibus was placed on the Index of Prohibited Books, and Galileo was warned not to teach Copernicanism.

GALILEO GALILEI BEFORE THE INQUISITION BY FRANCOIS FLEURY-RICHARD. This nineteenth-century painting of Galileo before the Holy Office dramatizes the conflict between science and religion and depicts the Italian natural philosopher as defiant. In fact, Galileo submitted but continued his work under house arrest and published, secretly, in the Netherlands. ¦ Would Galileo himself have subscribed to the message of this much later painting, that religion and science were opposed to one another?