History of Cosmology
In a recent post, I set forth a three part history of knowledge, drawing on, but not identical to, Michel Foucault’s archaeology of human sciences in The Order of Things. It goes something like this:
Period Knowledge is
1300-1600 The Renaissance hidden in the world
1600-1800 The Enlightenment best way of comprehending the world
1800-1950 The Modern Period historical state of belief about the world
Foucault goes on to label the categorization of knowledge in these periods as Similitude (recognizing the hidden correspondences), Taxonomy (applying the right framework within which everything fits), and History (understanding the progression of ideas and events in time). My last post looked the history of biological knowledge. This one covers how we look at the planets and the universe.
In the Renaissance, the universe was seen as an ordered whole. The now famous Ptolemaic picture of the earth surrounded by planets traveling in concentric sphere represented more than a picture of the physical universe. Throughout the Middle Ages, it had developed into a set of symbols for understanding the forces at work in the world. (C.S. Lewis has a lovely analysis of this in his book The Discarded Image.)
Dante’s Paradiso demonstrates the medieval mindset, with each of the farther heavens demonstrating greater virtue until we hear of the Empyrean, the realm of true light beyond the orb of the stars. This is not an astronomical observation, but an anagogical (teaching) tool, meant to speak of what it means to achieve true blessedness.
Renaissance thinkers believed that the courses of the planets both signaled and activated events on the earth. The concept of similitude captures the idea that we participate in heavenly events (“as above, so below”) making astrology more about seeing the underlying patterns than believing it was a simple question of cause and effect (history). The word influenza, for example, comes from an idea that heavenly bodies “influence” earthly disease.
Copernicus’ motivation for removing the Earth from the center was not, for good or ill, based solely on the data. It was an attempt to preserve the dignity of the Sun over that of Earth. His new model (On the Revolutions of the Heavenly Spheres 1543) also worked with the data, but it would take the observations of Tycho Brahe and the mathematics of Johannes Kepler (A New Astronomy 1609) to provide a theory truly better than that of Ptolemy. (See Owen Gingerich’s The Book Nobody Read.)
For the next 200 years, the universe was viewed as a clockwork mechanism. No longer a teaching tool for the ascent of the soul, it was viewed instead as evidence of the regularity and precision of God’s craftsmanship. It was a wound up clock, keeping perfect time for the inhabitants of Earth. The planets were subsumed in a catalog of heavenly events that included stars, comets, and eventually galaxies.
Brahe was one of the first of several generations astronomers funded by princes (and the occasional cardinal) to catalog events in the heavens and figure out how to figure out navigation. With the rise of exploration by sea, it was important to know where you were when there were no terrestrial landmarks. (See Dava Sobel’s Longitude.) This process of cataloging culminated in Charles Messier’s catalogue (1774) of non-star, non-comets that nonetheless kept their position in the sky. Today we know them to be star clusters, galaxies, and nebulae. Astronomy progressed by the tabulation and taxonomy (systematic naming) of observed objects and events.
Enlightenment astronomy comes to an end with the idea that the universe is not stable, but expanding. Some of Messier’s objects proved to be distant galaxies racing away from the Earth, and as we understood them better, we began to understand that they reveal a changing universe. George LeMaitre proposed (1927) and Edwin Hubble championed (1929) the idea of an expanding universe. We have entered an age when the heavens must be viewed as changeable, just as things on earth are changeable. They have their own history and context.
Similarly we have come to the think of the Earth as an evolving planet, whose features change through gradual natural processes (James Hutton and Charles Lyell, late 18th c.) and whose continents move (Alfred Wegener The Origin of Continents and Oceans 1915). Even atoms and subatomic particles have lifetimes. And so we find that earth is fixed neither in space nor time, but part of a process.