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 of Earth?
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.
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
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 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
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.