Sunday, October 16, 2011

I hate hate hate the new Thinkprogress format. I can't seem to comment on Yglesias.

He waved a red flag in front of this bull with a post on "The Copernican Revolution in Macroeconomics." I am too upset to read the part on macroeconomics, but I assert that his claims about Ptolomaic and Copernican astronomy are totally incorrect.

the Copernican Revolution in astronomy. Not the potted 7th grade story of linear progress, but the tale told in Thomas Kuhn’s somewhat revisionist book.

The way this went was as follows. Ptolemaic astronomy started with the observation that “the planets” (including the sun and the moon) seem to revolve around the earth. It assumed they moved in circular orbits, and made predictions based on that. As people bothered to pay attention, it became clear that this theory gives you the wrong predictions. So people developed the ad hoc concept of “epicycles.” The planets moved in circles-within-circles, with equations developed to account for the actual position of the planets. With more and more observations, the calculations became more and more complicated and a lot of people were unhappy with the increasingly messy picture. Then along comes Copernicus who as a young man had been involved in some neo-Platonist cults featuring sun-worship and a heliocentric worldview. He notes that if you reinterpret the heavens as centered around the sun, you can derive a considerably more parsimonious and theoretically elegant account of positions of various heavenly bodies. All the epicycles are gone! Victory.

Yglesias's final claim of fact is simply totally undeniably 100% false. Copernicus did not eliminate all epicycles. The Copernican model has epicycles.

Ask the Wikipedia

For philosophical reasons, Copernicus clung to the belief that all the orbits of celestial bodies must be perfect circles[2] and to a belief in the unobserved crystalline spheres. This forced Copernicus to retain the Ptolemaic system's complex system of epicycles, to account for the observed deviations from circularity and to square his calculations with observations.

Now that wasn't so hard was it ? I understand that it is hard to get the facts straight on a breaking story about what was published in a book in 1543, but I think that claims of fact should be accurate and if it is not worth botherin to get them right then it is not worth making them.

Furthermore, Ptolemaic astronomy started with Ptolemy who included epcicycles and much more complicated things. The claim made by Kuhn and many many others that Ptolemaic astronomy got more and more complicated is supported by absolutely zero primary evidence.

The unsupported claim is accepted as true, because it has been made in so many secondary sources, but there is no document from the time of Copernicus or earlier which demonstrates that Ptolemaic models were made more complicated after Ptolemy'ss original model. In contrast, there is evidence that Ptolemy's original model was used by Copernicus.

The claim that the Ptolemaic model was fiddled to fit the data, because the original model didn't work is not supported by any legitimate historical evidence.

I have not read the post after the quoted passage. I am too upset and afraid my head will explode.

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