Precession

1. Precession Eric Angat Teacher

2. Copy and answer the following questions. • What is precession? • What is the orbital tilt of Earth? • What are the two factors that causes the precession of Earth? • What is our current north star?

3. http://www.youtube.com/watch?v=0qHjtp4cdCA

4. Imbalance on the distribution of lands. flattening Earth's daily rotation at about 1,000 mph. This produces flattening at the poles and bulging at the equator. bulging bulging flattening

5. What is Precession? precession nutation Earth’s axis rotation Remember: Earth’s axis is only an imaginary line. Earth

6. Comparing Rotation and Precession PRECESSION ROTATION Earth’s axis spins. Earth spins. Spinning Day and night. Changes our North star. 24 hours 26,000 years

7. What is Precession? Precession is the rotation of Earth’s axis. precession nutation Earth’s rotation takes 24 hrs. while Earth’s axis rotation takes 26,000 years. Earth’s axis rotation Earth

8. What is the orbital tilt of Earth? Earth’s orbital tilt is 23.5 degrees. This tilt is responsible for the seasons on Earth.

9. 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.

10. What are the two factors that causes the precession of Earth? The orbits of Earth and moon are not on the same plane causing the gravitational imbalance. 2. Uneven gravitational pull of the moon and the Sun.

11. Uneven gravitational pull Precession happens because moon’s orbit is tilted from the Earth’s elliptical plane

12. Precession is similar to a spinning top. http://www.youtube.com/watch?v=uVyhyNvlN3Y

13. What is our current North star? Earth’s current northern star is Polaris. Thousands of years from now it would be Deneb. Earth’s axis

14. Thuban (Alpha draconis) Polaris Vega Deneb Constellations-group of stars forming a shape.

15. Polaris

16. Copy and answer the following questions. • How long is Earth’s complete rotation on its axis? • What is the direction of Earth’s rotation? • How long is Earth’s complete revolution?

17. http://www.youtube.com/watch?v=lkWyM-M8o0c

18. Copy and answer the following questions. • How long is Earth’s complete rotation on its axis? • 6. What is the direction of Earth’s rotation? • 7. How long is Earth’s complete revolution? Earth complete rotation takes 23 hours and 54 minutes Earth rotates counterclockwise. Earth’s complete revolution takes 365.26 days

19. 8. The spinning motion of Earth’s rotation causes it to bulge at the ________. • North pole • South pole • Equator • hemisphere Equator

20. 9. Earth rotation on its axis • causes _____________. • seasons • weather • tide • day and night day and night

21. 10. Earth’s Northern star changes because of_____________. The cycle completes every 26,000 years. • rotation c. nutation • precession d. revolution precession

22. 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? • northern star • gravity • seasons • tide

23. 12. PRECESSION or the rotation of the Earth’s axis changes our _____________ every few thousand years. northern star • northern star • gravity • seasons • tide

24. 13. Why does Earth experience precession? because the Earth revolves around the sun every 365 days because of the movement of the circumpolar stars and Polaris because the Earth is the third planet from the sun because the plane of the moon’s orbit is tilted from the Earth’s elliptical plane

25. Vocabulary Words: • 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.