Earth rotates on its axis, causing day and night. It also revolves around the sun in an elliptical orbit, completing one revolution in 365.25 days. Earth's axis is tilted at an angle of 23.5 degrees, resulting in seasons. Earth's rotation causes it to bulge at the equator and precess slowly over thousands of years.

1. S
Earth’s Motions
Rotation – Revolution - Precession

2. • At all times, half of Earth is illuminated
by the sun and half is in the dark.
• Daytime and nighttime are the result of
Earth’s rotation on its axis.
• Earth’s axis tilts at an angle of 23.5°
and points toward the North Star.
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LEARNING TARGETS

3. Earth’s Rotation
• The spinning of Earth on its axis is called rotation.
• The “AXIS” is an imaginary line passing through
Earth’s center through the N. and S. Poles.
• The Sun will illuminate only half the Earth at a time.
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Obliquity Flash

4. Earth’s Rotation
• Rotates Eastward (From West – East)
• Counter-clockwise in Northern Hemisphere.
• Clockwise in Southern Hemisphere
• Sun appears to rise in the East and set in the West.
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Sun in Sky Flash

5. Earth’s Rotation Causes…
1. Earth to stay upright in orbit.
2. Bulge at the equator – oblate spheroid shape
3. Day and Night
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6. Earth’s Rotation Causes…
1. Earth to stay upright in orbit.
• The Earth is tilted 23.5°
• The N. Pole points toward the star Polaris
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Spinning Earth – Click
Here
Non Spinning Earth –
Click Here

7. Earth’s Rotation Causes…
2. Earth to bulge at the equator
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• Poles – rotation is almost 0 mph
• US-Latitudes – rotation is between 700 – 900 mph
• Equator – rotation is 1000 mph

8. Earth’s Rotation Causes…
3. Day and Night
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• DAYTIME: When we are on the side of Earth facing the
sun.
• NIGHTTIME: When we are on the side of Earth opposite
the sun.
• 1 rotation = 24 hours
(1 day)

9. Earth’s Rotation Causes…
3. Day and Night
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• It is Earth that is
moving (rotating).
• The Sun is stationary
(almost)
• The Sun just appears
to move.

10. Earth’s Rotation
• Check your understanding…
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11. DAY NIGHT THINK QUESTIONS

12. Evidence of Rotation
• Foucault Pendulum
• A pendulum is suspended above Earth’s surface.
• Once a pendulum is set in motion it will continue to move in the
same direction.
• The Earth spins underneath the pendulum.
• The Pendulum seems to change directions because Earths
rotation.
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Pendulum Flash

13. Earth’s Precession
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 A slow movement/changing of direction around
a point or axis of a spinning body.
 The top does not fall over as long as it stays
spinning.

14. Earth’s Precession
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 The Earth “wobbles” on its axis once every
26,000 years.
 Earth’s precession moves opposite to its
rotation.
 Earth’s axis will not straighten due to this
constant rotation. Spinning Earth – Click
Here
Non Spinning Earth –
Click Here

15. Moving toward Vega
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16.  The movement of one object around another object is called
revolution.
 While Earth spins, it also moves around the sun.
 Earth revolves counterclockwise (N. Pole) around the sun at
66,000mph .
 1 Revolution takes 365.25 rotations (days).
 A day is added to the calendar every 4 years in February to account
for the extra 0.25 day rotation.
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EARTH’S REVOLUTION
01_earthsun_Flash

17.  The movement of one object around another object is called
revolution.
 While Earth spins, it also moves around the sun.
 Earth revolves counterclockwise (N. Pole) around the sun at 66mph .
 1 Revolution takes 365.25 rotations (days).
 A day is added to the calendar every 4 years in February to account
for the extra 0.25 day rotation.
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EARTH’S REVOLUTION
01_earthsun_Flash

18.  The path Earth takes around the sun is called an
orbit.
 Earth’s orbit is in the shape of an ellipse (flat oval)
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EARTH’S REVOLUTION
0408_rotatingearth_Flash

19.  The sun is closer to one side of the ellipse than the other.
 Perihelion – point along Earth’s orbit when Earth is
closest to the sun. (JANUARY)
 Aphelion – Point along Earth’s orbit when Earth is farthest
from the sun (July)
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EARTH’S REVOLUTION