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Movements of Earth

Movements of Earth. Vocabulary. Rotation Revolution Precession Perihelion Aphelion Perigee Apogee Solar eclipse. Lunar eclipse Nutation –will cover Barycenter-will cover Elliopsoidal Model-will cover. Revolution.

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Movements of Earth

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  1. Movements of Earth

  2. Vocabulary • Rotation • Revolution • Precession • Perihelion • Aphelion • Perigee • Apogee • Solar eclipse • Lunar eclipse • Nutation –will cover • Barycenter-will cover • Elliopsoidal Model-will cover

  3. Revolution • Period of REVOLUTION= one complete elliptical orbit around the sun or planet (moon). • Earth=364.26 Why do we need a leap year? • Mercury=88 days • Pluto=248 Earth years • Planets revolve in a counterclockwise direction around the sun.

  4. Rotation • The period of ROTATION= movement of planet around its axis.=1 day/night cycle. • Earth=24 hours • Mercury=59 Earth days • Pluto=6 Earth days

  5. Tilt • The Earth is tilted on a 23.5 o angle on it’s axis • http://www.josleys.com/show_gallery.php?galid=313 • The tilt of Earth is the reason day and night are not 12 hours each and why we have seasons. • The side of the planet tilted towards the sun, is receiving more direct sunlight and longer days=summer. • The side of the planet tilted away from the sun, is receiving less direct sunlight and shorter days=winter.

  6. Tilt • http://www.learner.org/jnorth/tm/ReasonsBack.html • Any planet that is tilted on its axis will have seasons. • Seasons are marked by specific dates: • Summer solstice June20/21 –sun is at highest point in the sky and longest day of the year. • Winter solstice Dec.21/22-the Northern hemisphere is at full tilt away from the sun and shortest day of the year. • Autumnal equinox Sept. 22/23-day and night are equal • Vernal equnox March 20/21 day-day and night are equal.

  7. Precession • Change in the direction of the axis but there is not change in the 23.5o tilt. • Changes the stars near the pole-Polaris (current) or Vega. • Does not affect seasons.

  8. Barycenter • http://spaceplace.nasa.gov/barycenter/ • The balance between the masses of the planets as they orbit. • In the case of the moon and the Earth-the moon doesn’t orbit the Earth’s exact center, but a point 1,710 km below the surface. This is where the masses balance each other. • Causes the sun to wobble-it is not stationary in the solar system. As planets tug on it with their gravity it wobbles, but never goes far from its barycenter.

  9. Nutation • A wobble around the Earth’s axis 1/2o change/18 year period. • Due to the moon and tides.

  10. Ellipsoid Earth • The Earth’s diameter is wider at the equator than at the poles-not a perfect sphere. • Caused by the rotation of the Earth and the centrifugal force perpindicular to it. • The earth has a molten core, tectonic plates, and a thin crust that can move; therefore there is a slight flattening.

  11. Phases of the Moon • Oreo activity • The amount of the moon lit up by the sun. • ½ of the moon is lit at all times. The amoutn visible depends on the location of the moon with respect to the sun and Earth. • The same side of the moon faces the Earth because its period of rotation about its axis and its revolution around the Earth are about the same.

  12. Eclipses • Solar eclipse-when the moon moved between the Earth and the sun. • New moon phases • Lunar eclipse-the moon is eclipsed when it moves it moves within the Earth’s shadow. • Full moon phases

  13. Solar eclipse

  14. Lunar eclipse

  15. Why don’t we always see them? • Moon’s orbit is inclined 5% so most of the phases its shadow misses Earth. • Must cross the plane of ecliptic for an eclipse to take place.

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