1. Our Solar System

2. Models of the Solar System Objectives:  Compare the models of the universe developed by Ptolemy & Copernicus  Summarize Kepler’s 3 laws of planetary motion

4. Aristotle (384-322 B.C.) Promoted a GEOCENTRIC model of the universe The universe revolves around ME But doesn’t explain the RETROGRADE motion

6. Retrograde Motion

7. PtolemyPtolemy (87-150 A.D.) epicycles

10. Copernicus (1500s A.D.) Proposed the HELIOCENTRIC model of the universe.

11. The arguments against the Heliocentric Model 1)If the Earth actually spun on an axis -- as required in a heliocentric system to explain the diurnal motion (day/night)of the sky-- why didn't objects fly off the spinning Earth?

12. 2) If the Earth was in motion around the sun, why didn't it leave behind the birds flying in the air?

13. 3)If the Earth were actually on an orbit around the sun, why wasn't a parallax effect observed? That is, as illustrated in the adjacent figure, stars should appear to change their position with the respect to the other background stars as the Earth moved about its orbit, because of viewing them from a different perspective

15. nus Copernicus SUN Copernicus put the SUN in the middle of our solar system=> heliocentric model

16. Galileo agreed with him & invented the first TELESCOPE just to prove that the Sun was in the center of our solar system.

17. Kepler (1571-1630 AD) First to explain the principles of how a telescope works First to suggest that the Sun rotates about its axis 3 laws of Planetary Motion Formulated the other’s ideas into Mathematical formulas  creating Kepler’s 3 laws of Planetary Motion

18. The First Law: Planets move in ellipses with the Sun at one focus.

20. APHELION PERIHELION

21. Astronomical Unit = 149 598 000 km

22. The 2 nd Law: A planet speeds up as it gets closer to the sun. So that the area of space covered is the same whether the earth is close to the sun or further away.

24. The 3 rd Law: the time it takes to orbit the sun is directly related to its distance from the sun.

25. GRAVITY Sir Issac Newton (1642-1727) explained that the planets move in ellipses around the Sun because of GRAVITY

26. Assignment: Kepler’s 3 Laws of Planetary Motion Handout

29. Comets follow the Kuiper Belt. The Kuiper Belt follows past Neptune's orbit to the other side of the Sun. There is an "Oort" cloud that's a spherical region of Comets on the Kuiper Belt.

30. What do you think this ghostly image is?