Transcript Precession
Precession Eric Angat Teacher Copy and answer the following questions. 1.What is precession? 2.What is the orbital tilt of Earth? 3.What are the two factors that causes the precession? 4.What is our current north star? http://www.youtube.com/watch?v=0qHjtp4cdCA Imbalance on the distribution of lands. Earth's daily rotation at about 1,000 mph. This produces flattening at the poles and bulging at the equator. flattening bulging bulging flattening What is Precession? precession nutation Earth’s axis rotation Earth Remember: Earth’s axis is only an imaginary line. What is Precession? precession nutation Earth’s axis rotation Earth Precession is the rotation of Earth’s axis. Earth’s rotation takes 24 hrs. while Earth’s axis rotation takes 26,000 years. What is the orbital tilt of Earth? Earth’s orbital tilt is 23.5 degrees. This tilt is responsible for the seasons on Earth. What are the two factors that causes the precession of Earth? 1. Earth’s shape is oblate spheroid. The spinning motion of Earth causes it to bulge at the equator. What are the two factors that causes the precession of Earth? 2. Uneven gravitational pull of the moon and the Sun. The orbits of Earth and moon are not on the same plane causing the gravitational imbalance. Uneven gravitational pull Precession happens because moon’s orbit is tilted from the Earth’s elliptical plane Precession is similar to a spinning top. http://www.youtube.com/watch?v=uVyhyNvlN3Y What is our current North star? Earth’s axis Earth’s current northern star is Polaris. Thousands of years from now it would be Deneb. Thuban (Alpha draconis) Polaris Vega Deneb Constellations-group of stars forming a shape. Polaris Copy and answer the following questions. 5.How is precession different from rotation? 6.What is the direction of Earth’s rotation? 7.How long is Earth’s complete revolution? Comparing Rotation and Precession PRECESSION ROTATION Earth spins. Day and night. 24 hours Spinning Earth’s axis spins. Changes our North star. 26,000 years http://www.youtube.com/watch?v=lkWyM-M8o0c Copy and answer the following questions. 5.How is precession different from rotation? Precession changes our northern star while rotation causes night and day. 6. What is the direction of Earth’s rotation? Earth rotates counterclockwise or West to East. 7. How long is Earth’s complete revolution? Earth’s complete revolution takes 365.26 days 8. The spinning motion of Earth’s rotation causes it to Equator bulge at the ________. a. North pole b. South pole c. Equator d. hemisphere 9. Earth rotation on its axis day and night causes _____________. a. b. c. d. seasons weather tide day and night 10. Earth’s Northern star changes precession because of_____________. The cycle completes every 26,000 years. a. rotation c. nutation b. precession d. revolution 11. NUTATION or the ½ degree wobbling around the precessional axis due to the uneven gravitational pull of the moon and the oblate shape of Earth affects which of the following? a.northern star b.gravity c.seasons d.tide 12. PRECESSION or the rotation of the Earth’s axis changes our northern star _____________ every few thousand years. a.northern star b.gravity c.seasons d.tide 13. Why does Earth experience precession? A. because the Earth revolves around the sun every 365 days B. because of the movement of the circumpolar stars and Polaris C. because the Earth is the third planet from the sun D. because the plane of the moon’s orbit is tilted from the Earth’s elliptical plane Vocabulary Words: 1. Rotation- earth spins on its axis - completes in 24 hours ( day and night) 2. Revolution –Earth spins around the Sun. - completes in 365 days (year). 3. Precession – Earth’s axis spins/rotates. - completes in 26,000 years. - changes our northern star. 4. Nutation- irregularity ( zig-zag) in Earth’s precession by ½ or 0.5 degree. - influences seasons. 5. Earth’s 23.5 degrees tilt on its axis is responsible for the seasons, not the distance from the Sun.