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The Earth

The Earth. 22-1. It’s a sphere!!!. Scientists knew it was a sphere LONG before we looked at the earth from space 350 B.C. Aristotle proposed the earth was round because it always cast a round shadow on the moon Sailors saw the top of an approaching ship before they saw the rest of it

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The Earth

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  1. The Earth 22-1

  2. It’s a sphere!!! • Scientists knew it was a sphere LONG before we looked at the earth from space • 350 B.C. Aristotle proposed the earth was round because it always cast a round shadow on the moon • Sailors saw the top of an approaching ship before they saw the rest of it • Actually it is not a perfect sphere – it bulges slightly at the equator and is slightly flattened at the poles

  3. The Earth rotates on its axis. • What does this cause? • http://www.classzone.com/books/earth_science/terc/content/visualizations/es0404/es0404page01.cfm?chapter_no=visualization

  4. Earth’s Magnetic North • The Earth produces a magnetic field. • The Earth’s magnetic field does not match up with the Earth’s geographic/rotational north pole.

  5. Revolutions • The Earth revolves around the sun once every year. • http://www.classzone.com/books/earth_science/terc/content/visualizations/es0408/es0408page01.cfm?chapter_no=04 • Earth’s orbit is an ellipse, so the Earth’s distance from the sun is not constant.

  6. Earth’s Tilt • The Earth’s axis is tilted 23.5⁰ • This causes: 1. day and night http://www.cs.sbcc.net/~physics/flash/LengthofDay.swf

  7. Earth’s Tilt (cont.) 2. The Seasons- the hemisphere that is tilted toward the sun receives more direct radiation from the sun.

  8. Earth’s Tilt (cont.)

  9. Equinoxes and Solstices • Because of the tilt of the Earth’s axis, the sun is usually above the equator or below the equator. • The sun is directly over the equator twice a year = EQUINOXES • Spring Equinox = March 20 or 21 • Fall Equinox = September 22 or 23 • On the equinoxes there are equal hours of daylight and nighttime.

  10. Equinoxes and Solstices (cont.) • Solstices – when the sun reaches its greatest distance north or south of the equator • Summer solstice = June 21 or 22 • Aka the longest day. • Winter solstice = December 21 or 22 • Aka the shortest day.

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