Ancient astronomers believed that: 1. The celestial domain consisted of perfect ether and objects moved with circular and constant motions. 2. The terrestrial domain consisted of imperfect elements that tended towards the center of the universe. 3. Ptolemy's geocentric model placed Earth at the center of the universe with celestial objects orbiting around it. This model was supported by naked eye observations like a lack of stellar parallax.

14. ANCIENT ATRONOMY

15. A. CELESTIAL DOMAIN
• The Celestial domain is perfect hence can only be made up of the perfect substance they called “ether”
and can only move in perfect motion: circular in path and constant in speed.

16. B. TERRESTRIAL DOMAIN
• The terrestrial domain objects are imperfect and that the tendency of things to attain perfection is the
cause of their motion. Meanwhile, they also believed that things, depending on their composition of
the elements — fire, air, water, and earth — tend to move towards the center of the Universe (center of
the Earth) or away from it with earth, naturally, as at the center. Fire and water naturally move away
from the center.

17. ASTRONOMY BEFORE THE INVENTION OF THE
TELESCOPE
• 1. fundamental difference between terrestrial and
celestial domains
• 2. circular paths of constant speeds for the celestial
objects being in their perfect state
Ptolemy's model: "Earth-centered," or "geocentric" Ptolemy thought
that all celestial objects — including the planets, Sun, Moon, and stars
— orbited Earth. Earth, in the center of the universe, did not move at all

18. THE FOLLOWING EXPECTED PHYSICAL OBSERVATIONS ON THE
SURFACE OF THE EARTH (TERRESTRIAL DOMAIN). THE
EXPECTATIONS ARE BASED ON THE ARISTOTELIAN PHYSICS
• a. If the Earth rotates about its axis, given the calculated circumference of the Earth by Eratosthenes all
objects must be moving at about 2,000 kph. But no one feels a strong breeze
• . b. The spinning Earth would cause object to fly out, which does not happen.
• c. Falling things would veer towards the west as they fall, the arrows are not seen to veer away from
intended target.
• d. Spinning or orbiting Earth would require enormous amount of constant force to keep it moving.

19. THE FOLLOWING NAKED EYE OBSERVATIONS SUPPORT THE
PTOLEMAIC SYSTEM WHERE EARTH DOES NOT MOVE (NOT
EVEN ROTATION ABOUT ITS OWN AXIS).
• a. No parallax of the stars, since the annual pattern of the planets does not change.
• b. The apparent size of the stars does not change.
• c. Some basic physics in the terrestrial domain is not observed.