Lesson 1: Models of the Solar System What Was the Geocentric Model? How Did the Heliocentric Model Develop?

What they used to think…

What Was the Geocentric Model? Earth in the center of the universe http://www.voki.com/pickup.php?scid=5866842&height=267&width=200

WHY!!!!!!

Ancient Observations Pattern of the stars didn’t change over time Stars seemed to move, but stayed in the same position relative to one another Observed 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

More Reasons Why…

Ptolemy’s Model (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

Whoops! They were wrong!

Heliocentric Model Sun in the center

How Did the Heliocentric Model Develop? 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

The Copernican Revolution (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

More Proof!

Brahe and Kepler (1500s) Tycho Brahe made more accurate observations Johannes Kepler (Tycho’s assistant) Figured out the shape of the planet’s orbit Elliptical (or oval shaped)

Galileo’s Evidence (Italian) Galileo convinced others that the heliocentric model was correct! (1610) Discovered 4 moons around Jupiter Not 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