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Earth as a Planet

Earth as a Planet. Earth’s position in space Not the center of the Solar System Elliptical orbit Plane of the ecliptic Shape & Size of Earth Oblate spheroid Motions of Earth Revolution Year Rotation Day Precession Epoch. Earth as a Planet. Revolution Our movement around the Sun

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Earth as a Planet

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  1. Earth as a Planet • Earth’s position in space • Not the center of the Solar System • Elliptical orbit • Plane of the ecliptic • Shape & Size of Earth • Oblate spheroid • Motions of Earth • Revolution • Year • Rotation • Day • Precession • Epoch

  2. Earth as a Planet • Revolution • Our movement around the Sun • Counter-clockwise • 93,000,000 mi. away • 66,000 mi./hr. (average) • Faster in winter, slower in summer • Kepler’s 2nd Law • 365.25 days to complete • How do we mark this time? • Sidereal year

  3. Earth as a Planet • Kepler’s 2nd Law The orbital speed of a planet varies so that a line joining the Sun and the planet will sweep over equal area in equal time intervals. 1mo. 1 mo.

  4. Earth as a Planet • Key variables in the causes of seasons • Tilt of the Earth’s axis • 23.5 degrees • Location of the Earth in its orbit • Latitudes as it Relates to the Sun • Equator – 0 degrees • Tropic of Cancer – 23.5 degrees N • Tropic of Capricorn – 23.5 degrees S • Arctic Circle – 66.5 degrees N • Antarctic Circle – 66.5 degrees S • An Analemma

  5. The Earth as a Planet • Seasons • 2 solstice • Solstice = “Sun stand still” • June 21 or 22 –Summer Solstice • December 22 or 23 – Winter Solstice

  6. The Earth as a Planet • Sun’s position in the sky • Summer Solstice • Rise - NE • Noon • Set – NW • Length of the day • Winter Solstice • Rise – SE • Noon • Set – SW • Length of Day

  7. The Earth as a Planet • Seasons • 2 equinox • Equinox = equal (day & night hrs.) • March 21 – Spring Equinox • September 21 – Fall Equinox • Sun’s position in the sky • Rise – directly east • Noon • Set – directly west • Length of the day

  8. Earth as a Planet • Rotation • East to west direction (here on Earth) • Also west to east (viewed from space) • 23:56:04 • 15 degrees/hr. • Foucault pendulum • Precession • 26,000 yr. cycle • Significance of the North Star

  9. The Earth as a Planet • A system of coordinates • Latitude • Parallels • Measures N & S • Runs E & W • Equator • Longitude • Meridians (long lines) • Measures E & W • Runs N & S • Prime Meridian • Greenwich, England

  10. The Earth as a Planet • Latitude & Longitude of St. Joseph, MO • 39 degrees 45 minutes 29.94559 seconds N • 94 degrees 47 minutes 6.49119 seconds W • Latitude & Longitude of Kansas City, MO • 39 degrees 06 minutes 34 seconds N • 94 degrees 35 minutes 18 seconds W

  11. Earth as a Planet • Measuring Time • AM – ante meridian • PM – Post meridian • Midnight • Noon • Solar day – 24:00:00 • Sidereal day – 23:56:04

  12. Earth as a Planet • The Moon • Rotation & Revolution • Synchronous • Same side always faces toward the Earth • Phases • New • Waxing Crescent • Illuminated area is increasing • 1st quarter • Waxing Gibbous • Illuminated area is increasing • Full • Wanning Gibbous • Last quarter • Wanning Crescent

  13. Earth as a Planet • Eclipses • Solar (New Moon) • Moon is between Earth & Sun • Umbra • Penumbra • Fig. 16.32 • Lunar (Full Moon) • Earth is between Sun & Moon • Eclipses do not happen every month • Moon’s orbit is inclined 5 degrees

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