Transcript How do we know that the Earth rotates?

Why do we have Day and
Night?
Rotation
What does Rotation mean?
Rotation occurs when something is spinning around an axis.
What are some examples of things that rotate?
Tops, Ballerinas, Figure skaters, cyclones, Tornadoes, a merry-go-round, Earth
How do we know that the Earth rotates?
1.
Star trails- trails made with time exposure, circular paths that occur
because the planet is moving and not stationary.
2.
Winds curve because of the Earth’s rotation.
3.
Ocean currents curve clockwise in the northern hemisphere, and
counterclockwise in the southern hemisphere.
4.
The movement of a pendulum. It does not actually move, it is the Earth
moving that causes the pendulum to appear to change the direction of its
swing.
What happens when the Earth
rotates?
1. Day and Night
2. It changes shape?
Night and Day
What causes night and day?
The rotation of the Earth
• The side of the Earth that is facing the sun has daylight, the side of
the Earth away from the sun has night.
• It takes 24 hours for the Earth to complete one rotation.
• The Earth is tilted on it’s axis at a 23.5 degree angle.
• The Earth’s tilt is always in the direction of the North Star.
• Because of the Earth’s rotation the sun appears to rise in the east and
set in the west.
Predict what happens to the shape
of spinning ball.
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Materials: Piece of construction paper Ruler
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Directions:
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A.
B.
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Pencil
Scissors
Glue
Cut your piece of paper in one inch wide strips lengthwise so that you have two long
strips of paper
Cross strips at center (so you have an X shape. Glue at cross
Bring four ends together, forming a sphere, glue in place.
Let glue dry.
Using thin dowel rod, poke a small hole in the paper at each intersection. Push the
dowel through so it acts as an axis for your paper sphere.
Hold the dowel between your palms and rub together so that your sphere is spinning.
Observe what happens to your sphere and record your answers to the questions
below.
What did you observe happening to the sphere as it was spinning?
What explanation can you give to explain why this change occurred in the
sphere?
What is the name for Earth’s true shape?
What is Earth’s rotation rate?
What would happen to the earth if it rotated faster? Why?
How fast is earth moving?
• A point on the equator of the rotating
earth is moving about 1000 miles per
hour.
Our orbit around the sun moves
earth about 67,000 miles per hour
Where are we in the galaxy?
Our solar system is rotating around
the galaxy at about 490,000 mph
• Our galaxy is going through space at
around 2,233,333 miles per hour!
Precession
• Change in the direction of the axis without
changing the 23.5 degree tilt.
What causes Precession?
• The pull of the sun and moon on the bulge
created by the spin of the Earth (Oblate
spheroid)
• As early as the Babylonians and Egyptians
noticed the precession of the Earth