Getting to Now.

1. Getting to Now. History of our understanding of the Night Sky 1.2.5 Astronomy - Components of the Solar System and Beyond (Universe) Understand that the Solar System in a galaxy in a universe composed of an immense number of stars and other celestial bodies.

2. Where to find this information? The information in this presentation is from the Tarbuck and Lutgens “Earth Science” Ninth Edition. Chapter 19: The Earth’s Place in the Universe. Look for the notes icon as pictured above to know when it is important to take notes!

3. Early Greeks (600BC-AD 150) Believed in the geocentric (Earth Centered) universe.. The Earth was a sphere that stayed motionless at the center of the universe. Orbiting the Earth were the Moon, Sun and known planets (any guess as to which planets?) Beyond these seven wonderers (planetai) lied a celestial sphere in which stars traveled on its axis around the earth.

4. Mercury Planet # 1 http://www.stp.isas.jaxa.jp/mercury/images/Mercury-MMO.jpg

5. The Geocentric Sphere http://physics.pdx.edu/telescope/site8/Astronomie1.html

6. Some Greeks Wised up. • Aristarchus (312-230BC) proposed the Heliocentric universe (sun centered) which better explained the motion of planets. • Eratosthenes (276-194 BC) extreemely clever and simple way of proving the earth was round.

7. Venus planet #2

8. Then there was Ptolemy. • Sheer stubbornness prompted Ptolemy to geometrically explain the odd motion of the planets as they traveled around the Earth • Back to the Geocentric model! • Though he was wrong, his system was widely accepted for many years to come.

9. Ptolemy's Model explained retrograde motion http://www.physics.hku.hk/~nature/CD/regular_e/lectures/chap04.html Retrograde Motion – the apparent westward drift of a planets motion.

10. Earth planet #3

11. Nicolaus Copernicus (1473-1543) • Convinced that the Earth was a planet like the other 5 (then known) planets. • Reconstructed the planets with the sun in the center again (remember this was called the __________ system. • So scared of the church at the time his work was only published on his death bed. • Understudy Giordano Bruno was burned alive for supporting these ideas.

12. Copernicus Model http://www.physics.hku.hk/~nature/CD/regular_e/lectures/chap04.html

13. Mars planet #4 http://www.nwrc.usgs.gov/world/images/mars.jpg

14. Tyco Brahe (1546-1601), and Johannes Kepler (1571-1630) • Used Stellar Parallax to determine the distance of objects. • Also derived laws that explained planetary motion. • Kepler notice that the paths of planets were affected when near other planets.

15. Stellar Parallax http://csep10.phys.utk.edu/astr161/lect/retrograde/copernican.html By observing an object by changing your position and comparing that objects positional shift to a distant background, you can easily determine the distance of that object.

16. Jupiter planet #5 http://www.astronomija.co.yu/suncsist/planete/planetestalevski/foto/jupiter.jpg

17. Kepler’s 1st Law The Kepler's first law states that the orbits of the planets around the Sun are ellipses with the Sun at one focus. One way to draw an ellipse is to pin down the ends of a string, then use a pencil to stretch out the string. The curve drawn is an ellipse and the positions of the two pins are the foci. http://www.physics.hku.hk/~nature/CD/regular_e/lectures/chap04.html

18. Kepler’s 2nd Law http://www.physics.hku.hk/~nature/CD/regular_e/lectures/chap04.html The Kepler's second law states that a line from a planet to the Sun sweeps over equal areas in equal intervals of time. This means when the planet is nearer to the Sun, it moves faster.

19. Saturn planet #6 http://www.rundetaarn.dk/dansk/observatorium/grafik/saturn.jpg

20. Kepler’s 3rd Law The Kepler's third law states that the square of a planet's orbital period is proportional to the cube of its average distance from the Sun. P2 = d3 p=period d=distance

21. Galileo Galilei (1564-1642) • Discovered the telescope. • Observed moons around Jupiter. • Discovered that Venus has phases like the moon. • Moons surface was not smooth. • The sun had spots (not perfect!) • 1630 placed under house arrest for his ideas. • 1992 was finally exonerated by the church.

22. Uranus 7th Planet

23. Sir Isaac Newton (1642-1727) • First law of motion – an object in motion will remain in motion until another force is acted on that object. • Law of universal gravitation – Every body in the universe attracts every other body with a force that is directly proportional to their masses and inversely proportional to the square or the distance between them.

24. ANY two masses will attract to each other. http://www.physics.hku.hk/~nature/CD/regular_e/lectures/chap04.html F = G M1 M2 / r2

25. Neptune 8th planet

26. Constellations • Pattern of stars in the night sky. • 88 constellations recognized • Even though the stars are close together in the sky, they are really millions of miles apart. • All the planets, Moon and Sun travel across 12 constellations called the zodiac (hence your zodiac sign).

27. Dwarf Planets Pluto Eris Ceres http://www.orionsarm.com/historical/Ceres.html