Ptolemy: Consolidating Knowledge

150 CE
- Ptolemy’s Almagest, Geography, and Tetrabiblos were written.
12th century BCE
- The stars are arranged into constellations by the Babylonians.
350 BCE
- Aristotle argues that the stars are fixed in place and Earth is unmoving.
135 BCE
- Hipparchus generates a catalog of more than 850-star positions and brightnesses.
964 CE
- Al-Sufi, a Persian astronomer, updates Ptolemy's star catalog.
1252
- The Alfonsine Tables, which list the positions of the sun, moon, and planets based on Ptolemy's theories, are published in Toledo, Spain.
1543
- Copernicus demonstrates that placing the sun at the center of the cosmos rather than Earth makes it far easier to predict the movement of the planets.

Ptolemy compiled all of the astronomical knowledge available at his time in Amalgest.
- A thirteen-book mathematical treatment of the phenomena of astronomy. It covers a wide range of topics, including how the earth was created, the movement of the sun, moon, and stars, eclipses, and an explanation of how long a month is.
The 17th-century star map makes use of Ptolemaic constellations.
- The number of stars per constellation ranges from 2 to 42.
In Ptolemy's depiction of the solar system, the heavens revolved around a stationary Earth at its center. To support his geocentric theory of the solar system, Ptolemy expanded and clarified Hipparchus' system of eccentric circles and epicycles.
Everything that could be seen from a northern latitude of about 32° was listed in Ptolemy's catalog of 1,022-star positions and 48 constellations in the area of the celestial sphere known to the Greeks.
To explain the motions of the Sun, Moon, and five planets at the time, Ptolemy's system required at least 80 epicycles.
He believed the planets and sun orbited the Earth in the following order: Mercury, Venus, Sun, Mars, Jupiter, and Saturn.
Mul Apin: A cuneiform tablet where the Babylonian constellations are listed.

Plinth: A massive rectangular stone block with one of its vertical sides perfectly aligned in the north-south plane.
- The top of the stone had a horizontal bar, whose shadow accurately indicated the height of the sun at noon.
He took daily measurements to determine the times of the solstices and equinoxes.
He believed that the sun's orbit around Earth was circular.

Ptolemy believed that the motions of the celestial bodies had a significant impact on what happened on Earth.
Along with a method for calculating planetary positions, Ptolemy also produced a thorough analysis of how those movements affected people.