1. Geocentric Model Earth Centered
Everything in the universe orbited around Earth
Supporters : Aristotle, Ptolemy, the catholic church

2. Heliocentric Model Sun centered
Supporters: Copernicus, Galileo, Newton

3. Aristotle (384 BC) Ancient Greek philosopher
wrote about several scientific ideas
His ideas were accepted by Western Civilization
Ideas supported by the Catholic Church
Believed the Universe was “Earth-centered” or “Geocentric”

4. Ptolemy (150 AD) Roman citizen that lived in Egypt
Worked as an astronomer
and a mathematician
Used mathematics to develop
models of the structure of the Universe
His model was Earth centered or “Geocentric”

5. Collected data when he made observations of the sky
Nicolaus Copernicus
Religious man who was also an astronomer
First astronomer to formulate a Heliocentric model
The“Heliocentric” model places the Sun as the center of the Universe.
Collected data when he made
observations of the sky

6. Helios = Sun Centric= Center
Copernicus’
Discoveries
1.Earth moved with a daily motion on its axis (rotation)
2. Also moved with a yearly motion around a stationary sun (revolution)
Heliocentric (Greek)
Helios = Sun Centric= Center

7. Scientific Revolution
Copernicus compiled his observations and wrote about his theory
He was reluctant to publish because he did not want to offend the church
His findings began the age of modern astronomy

8. Johannes Kepler
Johannes Kepler's Laws of Planetary Motion : Kepler's laws challenged Aristotle and Ptolemy.
His studies showed that the Earth moved, in elliptical orbits.

9. Galileo Galilei
Made improvements to the telescope which led to better observations of the night sky
Galileo’s Model
Ptolemy’s Model

10. With his more powerful telescopes, Galileo began making astronomical discoveries including…
mountains and valleys on the moon
The four largest satellites of Jupiter, now called the Galilean moons
Sunspots
image courtesy of NASA

11. Beginning in 1610, Galileo began making observations of Venus and its phases.
The observations gave further evidence to support the heliocentric model by Copernicus (100 yrs later).
Galileo wrote AND PUBLISHED a book called the Starry Messenger, which supported the Heliocentric model of the universe.
Making his Heliocentric ideas public upset the Catholic church. Luckily, he was friends with the Pope, and he was only sentenced to house arrest for the rest of his life because of his work.

12. Sir Isaac Newton
Developed laws of motion that helped support Kelpler’s laws
Provided further evidence to support the heliocentric model
The ban on the heliocentric model was lifted after Newton’s discoveries