1. F.D.G.s # 4 & 5(Famous Dead Guys # 4 & 5)Copernicus and Galileo

2. Nicholas Copernicus (Feb. 19, 1473- May 24, 1543) Became unhappy with Ptolemy’s theory for the motions of the planets

3. Copernicus’ heliocentric Solar System All of the planets go around the sun, although the moon does go around the earth

4. Heliocentric Model • Heliocentric model = Sun centered Universe

5. Retrograde motion in an easy to assemble package! • Copernicus’ model could more easily explain the motion of the planets than could Ptolemy, with less complexity.

6. We don’t need no stinkin’ wheels! • Copernicus’ model didn’t require complex epicycles like Ptolemy’s did.

7. Time to publish… • De revolutionibus orbium coelestium • “On the revolutions of the celestial (Heavenly) spheres”

9. Copernicus’ Model • Figured the length of time the planets take to orbit the sun from observations of how long they take to re-appear at the same place in the night sky • Also figured out the distances to the planets

10. Copernicus’ Model cont… • The Earth’s center is not the center of the Universe • Religion? • The center of the Universe is near the Sun • The rotation of the Earth accounts for the apparent daily rotation of the stars

11. Copernicus’ Model cont… • The annual movements of the Sun are caused by the Earth revolving around it, not the Sun moving around the Earth.

12. Copernicus’ Model cont… • Retrograde motion of the planets is caused by the motion of the Earth, from which we (on the Earth) observe it

13. How good was Copernicus’s model? • He could not really predict the motions of the planets in the sky more accurately than Ptolemy because he stuck with the idea of uniform circular motion • Needed Kepler’s help • Thus he couldn’t entirely get rid of epicycles

14. Father of modern observational astronomy F.D.G – Galileo Galilei (1564 – 1642)

15. Galileo Galilei • First to use a telescope for observational astronomy • C.S.M. He DID NOT invent the telescope, rather he was the first to use it extensively for astronomical observations.

16. Galileo Galilei • Published his acceptance of Copernicus’ theory of the Universe • Described views of the moon with mountains, craters and dark lunar “seas”

17. Galileo Galilei • Discovered moons of Jupiter • Proved not all objects revolve around the Earth

18. Galilean Moons • (In order of distance from Jupiter: Io (the most volcanically active body in the solar system), Europa (suspected to contain a liquid ocean under its frozen surface), Ganymede (the largest satellite in the solar system), and Callisto. Both Ganymede and Callisto are larger than Pluto and Mercury. )

19. Galileo and Venus • Discovered that Venus has phases, just like our own moon

22. Galileo as an Author • Published Dialogue on the Two Great World Systems as a dialogue between two philosophers supporting Copernicus, and a layman supporting Ptolemy

23. Busted!!! • Called before Inquisition in 1632, where the book was condemmed • Galileo sentenced to house arrest for the rest of his life

24. R.I.P. • Died in 1642 • Buried in Florence, Italy

25. Geo vs. Helio Helio Geo