| Chapter 1: | The New Astronomy |
speaking—a minutum, which contrasted sharply with the Copernican immensum. In addition, it occurred to Tycho that the different apparent brightnesses of the stars could result from their being at different distances, and he was able to rationalize a stellar distribution of thickness of about 1,000 Earth radii. Of course, as the stars rotated in unison about the Earth, they had to maintain the same positions relative to one another somehow, and at the same time, the outermost layer of this shell needed material that was opaque in order to keep out information that might pour into physical space from the surrounding Empyrean.
Toward the end of the sixteenth century, Tycho fell into disfavor with the new Danish King Christian IV (1577–1648) and exiled himself. He ended up in Prague, capital of Bohemia, where he sought the aid of the mathematician Johannes Kepler (1571–1630). Tycho wanted Kepler to apply the data he had collected in order to put his hybrid World model on a more secure mathematical foundation, but Tycho died in 1601 before anything came of it, whereupon Kepler abandoned that project and instead used Tycho's data to improve the Copernican model. Kepler discovered that at least one planet (Mars) moved in an ellipse. This and a second related discovery appeared in Astronomia nova…Commentariis de Motibus Stellae Martis (“The New Astronomy…Commentary on the Motion of Mars”) in 1609, in which he enunciated the two empirical laws of planetary motion now known as the Law of Ellipses and the Law of Areas. The former states that all planets move in ellipses with the Sun located at one of the foci of the ellipse, and the latter states that in so doing, an imaginary line joining a planet to the Sun sweeps out equal areas in equal times. A third discovery came ten years later in Harmonices Mundi (“The Harmony of the World”), and all three helped verify Isaac Newton's (1642–1727) theory of gravitation .
The Infinite Universe
In the fifteenth and sixteenth centuries, the infinitude of theological space was a common topic for debate, but few ventured to revive the doctrine that physical space was unlimited. Pythagorean concepts had reemerged