08 - Geography 1111 8/20/08 Earth-sun geometry 1. Motions...

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Geography 1111 8/20/08 Earth-sun geometry 1. Motions of the earth 2. Reasons for seasons 3. Day length and solar intensity 4. Solstices and Equinoxes Summertime, day lengths get longer and longer as you reach the north pole. Wintertime, day lengths get longer and longer in the south. Sun rises in the east and sets in the west. Of all hours in a year, all locations experience 50% darkness and 50% daylight. Motions of the Earth Rotation Spin of the earth on its axis The motion that gives us day and night Takes 24 hrs Counterclockwise when viewed from above the N Pole. Revolution Orbit of the earth around the sun. Takes 365 ¼ days Defines our year Counterclockwise when viewed from above our N Pole Orbit is elliptical-3% difference in receipt of sunlight) o Perihelion (Jan 3)—91.5 million miles away o Aphelion (July 4)—94.5 million miles away Mechanical reasons for seasons 1. Sun supplies 99.9% of all energy on the earth. 2. Earth/sun orbital plane is called the ecliptic.
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08 - Geography 1111 8/20/08 Earth-sun geometry 1. Motions...

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