Earths Motions

Earths MotionsRotation Revolution - Precession

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At all times, half of Earth is illuminated by the sun and half is in the dark.

Daytime and nighttime are the result of Earths rotation on its axis.

Earths axis tilts at an angle of 23.5 and points toward the North Star.2Learning Targets

Earths RotationThe spinning of Earth on its axis is called rotation.The AXIS is an imaginary line passing through Earths center through the N. and S. Poles.The Sun will illuminate only half the Earth at a time.

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Obliquity Flash

Earths RotationRotates Eastward (From West East)Counter-clockwise in Northern Hemisphere.Clockwise in Southern HemisphereSun appears to rise in the East and set in the West.

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Sun in Sky Flash

Earths Rotation CausesEarth to stay upright in orbit.Bulge at the equator oblate spheroid shapeDay and Night

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Earths Rotation Causes Earth to stay upright in orbit.

The Earth is tilted 23.5The N. Pole points toward the star Polaris

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Spinning Earth Click HereNon Spinning Earth Click Here

Earths Rotation Causes Earth to bulge at the equator

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Poles rotation is almost 0 mphUS-Latitudes rotation is between 700 900 mph Equator rotation is 1000 mph

Earths Rotation Causes Day and Night

8DAYTIME: 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)

Earths Rotation Causes 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.

Earths RotationCheck your understanding

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DAY NIGHT THINK QUESTIONS

Evidence of RotationFoucault PendulumA pendulum is suspended above Earths 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

Earths Precession13A 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.

Earths Precession14The Earth wobbles on its axis once every 26,000 years.Earths precession moves opposite to its rotation.Earths axis will not straighten due to this constant rotation.

Spinning Earth Click HereNon Spinning Earth Click Here

Moving toward Vega15

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.16Earths Revolution

01_earthsun_Flash

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.17Earths Revolution

01_earthsun_Flash

The path Earth takes around the sun is called an orbit.Earths orbit is in the shape of an ellipse (flat oval)18Earths Revolution

0408_rotatingearth_Flash

The sun is closer to one side of the ellipse than the other.Perihelion point along Earths orbit when Earth is closest to the sun. (JANUARY)Aphelion Point along Earths orbit when Earth is farthest from the sun (July)19Earths Revolution