Download
1 / 24
240 likes | 358 Vues
Dive into the fascinating world of early astronomy, which compels us to look upward, as envisioned by Plato. This discussion examines the movements of celestial bodies like stars, the Sun, Moon, and planets, and how they were understood in ancient times. Questions arise about whether the Earth is stationary or in motion. We explore hypotheses regarding the apparent circular motions of these celestial objects, their rotation around the Earth or the Sun, and the observed movements of the five visible planets: Mercury, Venus, Mars, Jupiter, and Saturn.
E N D
Keep Looking Up Topic 2 Part 1
``Astronomy compels the soul to look upward and leads us from this world to another.'' - Plato
The celestial sphere appears to rotate about the celestial poles (completing one cycle in one day).
Celestial north pole stays still (North star aka Polaris) • Stars appear to move in counterclockwise fashion.
Question: What causes the observed circular motions of the stars, Sun, Moon, and planets about the celestial pole? • Hypothesis 1: The Earth is stationary, and the stars, Sun, Moon, and planets revolve around it. • Hypothesis 2: The stars, Sun, Moon, and planets are not revolving about the Earth; it is the Earth which is rotating about its polar axis, once per day.
The Sun moves west to east relative to the stars (completing one cycle in one year).
Question: What causes this apparent motion of the Sun relative to the background stars? • Hypothesis 1: The Earth is stationary, and the Sun revolves around it at a slightly slower rate than the celestial sphere does. • Hypothesis 2: The Earth revolves around the Sun, once per year.
The Moon moves west to east relative to the stars (completing one cycle in one month).
Question: What causes this apparent motion of the Moon relative to the background stars? • Hypothesis 1: The Earth is stationary at the center of the universe, and the Moon revolves around it a a slower rate than the celestial sphere does. • Hypothesis 2: The Moon revolves around the rotating Earth, once per month.
The planets sometimes move west to east, sometimes east to west, relative to the stars.
Wanderers • Only 5 planets to the naked eye. • Mercury, Venus, Mars, Jupiter, Saturn
