Download - Lesson 1: Models of the Solar System
What Was the Geocentric Model? How Did the Heliocentric Model Develop?
Earth in the center of the universe
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Pattern of the stars didn’t change over timeStars seemed to move, but stayed in the
same position relative to one anotherObserved planets moving among the stars
Early observers thought Earth was at the center of the universe (Chinese) Thought Earth was under a dome
of stars (Greek) Thought the Earth was inside
rotating spheres nested inside each other Ge is Greek for “Earth” Geocentric model: Earth is at the
center of the revolving planets and stars
(140 A.D.) Ptolemy further developed the geocentric model (Greek)
Planets moved in small circles carried along in bigger circles
Explained motions in the sky fairly accurately
Accepted for nearly 1,500 years
Sun in the center
Aristarchus developed a sun-centered model (Greek)
Helio (Greek for “sun”)
The Earth and other planets go around the sun
Not well received in ancient times
(1543) Nicolaus Copernicus worked out the arrangement of the known planets and how they move around the sun
More evidence was needed to convince many people
(1500s) Tycho Brahe made more accurate observations
Johannes Kepler (Tycho’s assistant) Figured out the shape of the planet’s
orbitElliptical (or oval shaped)
(Italian) Galileo convinced others that the heliocentric model was correct!
(1610) Discovered 4 moons around JupiterNot everything in the sky
revolved around Earth Venus goes through
phases similar to the moon It would not have a full
set of phases if both it and the sun circled around Earth