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Historical Clarifications

In the recent battle of words between Darian Unger G and Glenn McMillon Jr. ’03, on the topic of creationism, I am firmly on the side of Mr. Unger. But as a student of the history of ideas, I fear that Unger has rather misstated several facts, which lends an air of over-hasty diatribe to his most worthy cause.

Unger refers to “refuters of the round earth concept” as “15th-century skeptics” [“Creation Evangelists Exposed,” Sep. 28]. The fact that the earth is roughly spherical was widely known in antiquity. Eratosthenes of Cyrene successfully measured the circumference of the earth by observing the penetration of sunlight to the bottom of widely spaced deep wells. Aristotle before him had also correctly described the earth as spherical; even the pre-Socratic cosmologists knew the earth was a ball. Never did this change; European thought maintained its true opinion of the shape of the earth until even the present day. The notion that anyone significant had believed in a flat earth was a 19th-century invention.

Unger also refers to “dogmatic doubters of the Earth’s revolution around the sun.” The monumental De revolutionibus orbium c lestium, libri VI was published in 1543. But Copernicus merely guessed right; he proposed what was, at the time, an inferior theory. The Ptolemaic theory, as improved by Arab and medieval scholars, continued to predict the motions of planets much more accurately than Copernicus ever could. In addition, the heliocentric theory had to contend with the lack of observed parallax.

Kepler did much to improve the theory, but the key works were not published until the seventeenth century -- in particular, the Astronomia Nova (1609) and the Harmonice Mundi (1619), which together contained his famed “three laws.” Even then, the heliocentric theory was only a little superior in explanatory power to the Ptolemaic system, and failed to address the parallax problem.

It was not until Isaac Newton’s Philosophiae Naturalis Principia Mathematica, published in 1687, that a theory thoroughly superior to the Ptolemaic was proposed; Newton’s theory provided predictions as accurate as the Ptolemaic, and explained the lack of observed parallax.

Thomas Bushnell