Kerry K. Kuehn

Honors Lecture: Aristotle, Ptolemy and Medieval Astronomy

ptolemaic

Today, I am giving a presentation on Aristotle, Ptolemy, and the Medieval worldview for an Honors class at Wisconsin Lutheran College.
ptolemaic

Today, I am giving a presentation on Aristotle, Ptolemy, and the Medieval worldview for an Honors class at Wisconsin Lutheran College.

The geocentric—or Earth-centered—worldview dominated the astronomical thinking of the ancients. According to this view, we on Earth are situated at the center of a series of vast concentric heavenly spheres. The stars—arranged in their permanent constellations— are fixed to the outermost sphere. As this celestial sphere rotates around us once per day, we on Earth see the stars rise in the east, traverse the sky, and set in the west.

After the time of Copernicus (the mid-1500's), the geocentric world-view was gradually supplanted by a heliocentric—or sun-centered—world view. Nevertheless, the geo-centric world-view still provides a simple and useful way of thinking about the motion of the sun, moon, planets and stars. Even today, astronomers map the locations of the stars on a celestial coordinate system that mimics the heavenly sphere of the ancients.