2. Heliocentric Solar System

3. BELLWORK: What did the solar system do when it wanted to have a party? plan it!

4. "Eppur Si Muove“ "(And, yet it moves!") Galileo Galilei (1564 – 1642) 1610 “Siderius Nuncius” (The Starry Messenger) Used a handmade telescope to view the sky.

5. The Moon has mountains, valleys, craters, just like Earth! So… we (Earth) is not so special. The objects in the solar system are similar. Galileo Galilei (1564 – 1642)

6. SUNSPOTS Sunspots on the Sun moved across the face of the Sun, so….. What is the sun doing? The sun must be rotating, spinning! So….. Does the Earth also spin, rotate?

7. Jupiter Has Moons! Galileo’s 4 Moons – Io, Europa, Calisto, & Ganymede Big Jupiter has several moons orbiting it! So….. Could the Sun have planets orbiting it too?

8. More evidence… With his telescope, Galileo observed that Venus has phases, just like our moon! Over the months of the year, Venus can be observed changing in size and going through phases

9. On your white boards, diagram the Sun, Venus and Earth Show the motion to describe the Earth observing phase on Venus

10. http://astro.unl.edu/classaction/animations/renaissance/venusphases.html animation

11. Nicholas Copernicus (1500 AD) (a thousand years after Ptolemy In Europe) “De Revolutionibus Orbium Coelestium” The HELIOCENTRIC Model

12. A New and Improved Model Using Galileo's observations with the telescope, Copernicus tried a different model, placing the SUN in the CENTER with the planets orbiting around it. HELIOCENTRIC Let’s see if it explains retrograde motion.

13. Earth 1 Sun 6 Mars orbit 5 4 3 2 Fixed Stars Planet's apparent path in the sky. Copernicus Explains Retrograde Motion 1 2 3 4 5 6

14. Earth 1 Sun 1 2 3 4 5 6 6 Mars orbit 5 4 3 2 Fixed Stars Planet's apparent path around sky. Fast Earth overtakes slower outer planets so they appears to slow down, move in reverse, and then move forward again with respect to the fixed stars. Copernicus Explains Retrograde Motion

16. “On the Revolution of the Heavenly Spheres” Earth is NOT the center of “everything.” The SUN is at the center of the solar system also, the Stars are much farther away than the Sun The apparent motion of the stars is a result of the Earth’s rotation Any observed movement of the Sun is due to Earth’s revolution (orbit) and rotation about the Sun. Retrograde Motion was much simpler to explain If…..