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 of Earth?

4.What is our current north star?

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

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

What is Precession?

precession nutation Earth’s axis rotation Earth

Remember:

Earth’s axis is only an imaginary line.

Comparing Rotation and Precession ROTATION Earth spins.

Day and night.

24 hours Spinning PRECESSION Earth’s axis spins.

Changes our North star.

26,000 years

What is Precession?

precession Earth’s axis rotation Earth nutation 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 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?

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

Copy and answer the following questions.

5.How long is Earth’s complete rotation on its axis?

Earth complete rotation takes 23 hours and 54 minutes

6. What is the direction of Earth’s rotation?

Earth rotates counterclockwise

.

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 a. North pole b. South pole c. Equator d. hemisphere

9. Earth rotation on its axis a. seasons b. weather c. tide d. day and night

10. Earth’s Northern star changes 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 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.