Perspective in Astronomy

The parallels between changes in astronomy and changes in art discussed in Hallyn's The Poetic Structure of the World has gotten me thinking about the introduction of perspective into art and astronomy.  Hallyn talks about this a little bit, but I want to engage in some wild speculation.  This is a blog, after all.

Here's my thought: the Aristotelian cosmos is like pre-perspective art, while Copernicus effectively introduced perspective into astronomy.  I can't back this up with any research, but I'll at least try a little bit to justify this idea (which I'm sure has been suggested by others, so it's not even new).  The Aristotelian cosmos is a hierarchical structure.  It has a geometrical arrangement to it, but the ordering is really a moral/philosophical one.  Perfection exists at the outer boundary.  Corruption at the center.  Christians would later adopt this moral structure by placing heaven outside of the sphere of stars, and hell at the center of Earth.  The universe has a moral order with bad at the center, increasing goodness as you make your way outward (so that man has a somewhat ambiguous location between heaven and hell, but much closer to hell), and perfect goodness at (or beyond) the outermost limit.

Likewise, much pre-perspective art was arranged hierarchically.  The most important figures in the scene were often placed at the top of the composition and they were usually much larger than the other figures.  Figures of less importance were at the bottom and were smaller.  There was little, if any, attempt to depict a realistic view of the 3D setting.  The only way to tell if one object was in front or behind another is if the images of the objects overlapped so that one image blocked a part of the other image.  But the spatial arrangement wasn't really what was important.  What was important was the hierarchy, the ordering by importance.  One has this sense of the Aristotelian cosmos: that the fundamental order was a philosophical one, and the geometric arrangement was just there to illustrate the philosophical hierarchy.  This becomes very explicit in Dante's Divine Comedy.

Ptolemaic astronomy was an attempt to construct geometrical motions that would fit into this philosophical space.  It never really quite succeeded.  There was always a tension between Ptolemy and Aristotle (not personally, since they didn't live at the same time, but you know what I mean).  Copernicus abandoned the philosophical space of Aristotle and tried to develop a geometrical theory that employs the ideas of perspective - the recognition that what we see is dependent upon our point of view.  In addition to making this fundamental step, Copernicus went further by introducing a new perspective which he felt was more fundamental than ours: the perspective of the Sun. 

You can argue that Copernicus was really just introducing a new Neo-Platonic or Hermetic or some such philosophical hierarchy, to replace the Aristotelian one.  That may be true.  If so, he certainly wasn't the last to try that.  Kepler very explicitly introduced a new hierarchical structure to the world, but his hierarchy is a hierarchy of harmonies.  It has a relation to the spatial structure of the world, but in a much subtler way than did Aristotle's.  And long after Kepler others tried to impose a philosophical/moral ordering on the universe that dictated a particular geometric structure: Stukeley and Wright both proposed explanations of the Milky Way that made use of such a moral-geometric ordering.

So even after astronomers recognized that the world could look very different depending on your perspective (the classic exposition of this is Kepler's Somnium, in which he describes what astronomy would be like if done form the Moon), they still continued to look for one particular perspective that was somehow better than all others.  The main thing that seems to have guided them in this search for the ideal perspective is a sense of harmony and order.  Apparently the same thing happened in art.  The artist, of course, must choose a perspective from which to depict his scene.  Not all choices were considered equal, and artists sought the choose the perspective that would produce the most harmonious composition.

Often this ideal perspective was couched in religious terms.  Copernicus did that a little, Kepler a lot.  Stukely and Wright were explicitly religious in their suggestions, giving Heaven and Hell specific locations in their models of the universe.  The view these men sought might be called the "God's Eye View".  But eventually the idea of God's omnipresence trumped this notion of a God's Eye View.  If God was everywhere, then there was no single location or point of view that was particularly God's.  In effect, this made all perspectives equally valid from a moral/philosophical point of view.  You see this with Bruno and again with Newton.  But Newton showed that some perspectives were better from a physical point of view (what we would now call inertial reference frames). 

Anyway, I find it interesting that the search for a harmonious and well-ordered model of the world was, at least in some cases, motivated by the desire to find the ideal perspective, God's perspective.  We still make use of harmony and order in guiding our search for scientific theories, but few scientists would claim that the search for harmony or symmetry is religiously motivated.  What, then, convinces us that scientific theories that are harmonious, well-ordered, symmetric, or beautiful are better than empirically equivalent theories which are not?   This is a question that I find deeply fascinating.