The Revolution of Ideas

The Beginnings of the Heliocentric Model �of the Universe

Unit 2: History of Astronomy

Copernicus�(1473-1543)

A Polish Astronomer

The Copernican Revolution!

Copernicus

1. Earth is not the center of “everything”

2. All the planets revolve around the Sun! (heliocentric theory)

3. Stars are very much farther away than the Sun

4. Any motion of the stars is a result of Earth’s rotation

5. Still used “perfect” circles for the orbits

Changing ideas is not easy…

On March 5, 1616, Copernicus' work was banned from being taught and discussed

It stayed on a list of prohibited books and teachings until 1822!!!! 

Copernicus was no fool. He waited until his own death before he published his new ideas.

Galileo Galilei (late 1500s - early 1600s)

• First to point the refracting telescope towards the sky 
• He studied the movement and orbits of many nearby planets in our solar system
• Offered PROOF to Copernicus’s heliocentric model of our universe

Galileo’s Proof

• 4 moons orbiting Jupiter (proves everything didn’t revolve around Earth)

• Venus goes through phases (it has to revolve around the sun in order for us not to see the whole lit side)

Tycho Brahe (late 1500’s)

• Had his own island for astronomical observations
• Engineered precise astronomical instruments and made the most precise observations of his time
• Observed a supernova in Cassiopeia
• COMBINED geo and heliocentric ideas
• All other planets revolved around the Sun, which revolved around Earth

Johannes Kepler (early 1600’s)

• Used math to calculate that planets moved in elliptical orbits
• Developed laws of planetary motion (more on that next week)

Kepler’s Planetary Diagram

Isaac Newton (mid 1600s)

• 3 laws of motion explain how the inertia of a planet with gravity causes orbital motion
• Developed the reflecting telescope

Today!