Tuesday, October 18, 2016

In a Glass Dome

So let us begin with a classic case of simplifying.
Ptolemy’s planets from the Encyclopaedia Britannica (1st Edition, 1771). Wikipedia

In this diagram of Ptolemy’s universe (developed ca. 150), planets revolve in epicycles around invisible points revolving around a stable earth. This explanation squared with the ancient belief that our earth was the center of the universe. 

Based on Nicolaus Copernicus' De revolutionibus orbium coelestium. Wikipedia
Move the sun to the center as Copernicus did in 1543, and the need for epicycles disappears. Natural philosophers had found Ptolemy’s explanation satisfactory for about 1200 years and resisted Copernicus’s. Beginning in 1609, however, Galileo began making observations with telescopes, producing a series of phenomena that made the geocentric model of the universe harder and harder to defend. However, even Copernicus, for whom the starry dome of the night sky overhead became the “immobile sphere of fixed stars,” did not get it all right.
The accuracy of the sun-centered explanation of the motion of the planets seems obvious to us now, since it is a so much simpler explanation. We often refer to Occam’s razor to explain the scientific preference for the simplest explanation, but William of Occam (1287-1347) was not the first one to formulate this idea; ironically, a much earlier statement of it, “We consider it a good principle to explain the phenomena by the simplest hypothesis possible,” was made by Ptolemy. However, another formulation of Occam’s razor is more precise in its application of simplicity: “Among competing hypotheses, the one with the fewest assumptions should be selected” (Wikipedia). 
The Ptolemaic model required many assumptions, some of which reached far beyond astronomy and were entangled with religious belief so that in the 16th Century, disassembling the world view based on the geocentric universe was hardly a simple act because the heliocentric view of the planets required a whole new view of the world.Religion functioned then as science does now: a universally accepted schema for explaining the world. For us, science predicts the future, tells us what to eat, heals us, speaks the obscure language of mathematics, explicates the stars and planets to us, and understands the mysteries of the invisible quanta, just as medieval Christianity did. If some discovery falsified crucial assumptions of the scientific process—the discovery that, for example, the earth is actually a computer simulation and the code has just been changed so that some conclusions already proven are no longer true—if such a proposition were itself proven, would we all embrace it immediately because it was a simple explanation for why some outcomes defied science? For the 16th Century, heliocentrism was not a simple solution.

Galileo’s proofs of the Copernican universe met with serious push-back, and he died while still in official disgrace, but later, when he was reburied in a place of greater honor, the middle finger of his right hand was removed from his body. Currently on display in a glass dome, it is suitably mounted in a vertical position, perhaps as a warning to those of us too invested in our assumptions to see the simple truth of our situation.

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