Episodes from the Early History of Astronomy

"In this book, Asger Aaboe selects a few significant "episodes" from early astronomy and treats them in detail, rather than attempting a general survey. First he gives a descriptive account of what one should see when one looks at the sky with the naked eye, unbiased by received knowledge, and with curiosity and wit. He then turns to the arithmetical astronomy of ancient Mesopotamia, where astronomy first became an exact science. Next are treated Greek geometrical devices accounting for planetary motion, culminating in Ptolemy's planetary models in his Almagest. Ptolemy does not here assign his models absolute size, but if properly scaled, they yield good values, not only of the directions to the planets, but also of the distances to them. In fact, there is evidence that Copernicus used parameters from the Almagest to find the dimensions of his system. There follows a discussion of modifications of Ptolemy's models by Islamic astronomers, who wanted to use only uniform circular motion, some of which Copernicus adopted. Aaboe concludes this section by clarifying precisely which problem was resolved by the heliocentric hypothesis, as well as by Tycho Brahe's arrangement."--BOOK JACKET.

Beyond its central premise, the book can be read through the connected lenses of Nonfiction. Those themes offer useful points of attention as the characters, ideas, or world develop, especially where the book complicates the expectations of its primary category.