Astronomy
Initial Paradigm: The Two-Sphere Universe
- Large sphere containing the stars on its surface rotates about a small sphere, the Earth, with a period = 1 day.
Anomaly: The Problem of the Planets
- Five planets exhibit anomalous (within 2 sphere paradigm) motion. ie for some part of the year, planets go “backwards”.
Normal Science Response: Ptolemy ? Tycho
- Planets move on circles (epicycles) centered on another circle (deferent = Sun for Tycho) which moves uniformly around the Earth.
Extraordinary Response: Copernicus ? Kepler
- Copernicus: All planets (including the Earth) move about the Sun.
- Kepler: abandons paradigm of uniform circular motion: Elliptical orbits (Sun at one focus) with a varying speed (equal areas in equal times)