Kepler’s theory of the solar magnet can be distinguished from his theory of species Immateriata. Kepler’scelestial hypothesis also required a motion perpendicular to the radius vector (the species Immateriata). Following Aristotle’s principles of motion, that motion required a mover, Kepler was oblidged to explain why the planets moved at all. Further, he was obliged to […]
Kepler’s Magnetic Planetary Theory
A simplified illustration of Kepler’s solar magnetic theory. As a given planet circles the sun, the position of the planet’s axis remains fixed and constant. The sun’s outer surface constitutes one magnetic pole while its center is the opposite magnetic pole. The planet is thereby attracted to the sun through one half of its orbit […]
Kepler’s Problem – The Second Law
Kepler’s Problem can be described as follows. In this diagram, AMP is an ellipse, ABP a circumscribed circle, S and F are foci, A and P the aphelion and perihelion, and M the planetary position. For any planetary position (M) on an ellipse, the time taken to move from A to M is to the […]
The Post-Keplerian Astronomers
Ward’s Elliptical Hypothesis
In the above diagram ABPD is an ellipse, S and F foci, A and P aphelion and perihelion; the planet is at E, and angle AFE (the middle anomaly) changes uniformly. As Seth Ward defined it, the problem is to derive angle ASE (the true anomaly) from knowledge of angle AFE. Calculation requires plane trigonometric […]
Mercator’s Elliptical Hypothesis
In the above diagram AEP is an ellipse with foci S and F, D is the apparent position of a planet; equal angles are swept out about F in equal times. AP is the line of apsides, C the center and M some point about C on the major axis. FM = 1/3FS, which Mercator […]
Boulliau’s Astronomia Philolaica – Assumptions
Assumptions of Philolaic Astronomy Planets have a simple motion in a simple line. Planetary revolutions are equal, perpetual, uniform. They should be regular revolutions or composed of regular revolutions. They can only be circular. Or composed of circles. Motions should have a principle of equality. Since they admit of a certain inequality, the center of […]
Ismael Boulliau – Astronomia Philolaica
BOOK I – CHAPTER XII WHETHER THE SUN MOVES THE PLANETS The solution to this problem cannot be achieved by Geometrical demonstration. Nevertheless, from reasons adduced in our Philolaus book 4, chapter 2, that which corresponds to reality seems more apt and congruent, and what becomes much more probable is that the planets and the […]
Borelli’s Critique of Boulliau’s Astronomia Philoaica (1645)
Johannes Kepler was the first, by his boldness, and in opposition to the ancient philosophers, to give the order which banished perfectly circular orbits from the sky; he proved most clearly from Tycho Brahe’s observations that confirmation was provided in the case of the orbit of Mars; then he noticed also that the ellipticity of […]
Read more "Borelli’s Critique of Boulliau’s Astronomia Philoaica (1645)"