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Earth’s Revolution and Seasons

Earth’s Revolution and Seasons. Definition. Revolution: The movement of Earth in its orbit around the sun. Evidence of Revolution. Positions of constellations in the sky appear to move as the Earth rotates (daily->rise and set) and revolves (seasonally-> ex. Only see Orion in the winter).

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Earth’s Revolution and Seasons

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  1. Earth’s Revolution and Seasons

  2. Definition • Revolution: The movement of Earth in its orbit around the sun

  3. Evidence of Revolution • Positions of constellations in the sky appear to move as the Earth rotates (daily->rise and set) and revolves (seasonally-> ex. Only see Orion in the winter)

  4. Parallax- (do not write) • The apparent shift in position of the stars • Cannot be detected with eye, but can be measured with precise instruments • Proof of Earth’s revolution

  5. Hold a pencil at arm’s length • Cover one eye • See what happens when you switch eyes but keep the pencil still • Viewing the pencil from two different position produces the same shift as seen in nearby stars

  6. Earth’s Movement • The Earth revolves counterclockwise when viewed from the North Pole. • Earth’s orbit is an ellipse (which is a stretched out circle)

  7. The average distance to the sun is about 93 million miles

  8. Perihelion vs. Aphelion • Perihelion (January 2): Closest to the sun (about 91 million miles) • Aphelion (July 4): Farthest from the sun (about 95 million miles)

  9. How Much Time? • Earth revolves once every 365.24 days • An ellipse is 360 degrees so we revolve ~1 degree each day

  10. Effects of Revolution • Effects: Changes in the seasons and variation in the length of day and night

  11. The Reason for the Seasons • The tilt of Earth’s axis and revolution causes the seasons

  12. The hemisphere of the Earth that is pointed toward the sun receives more direct sunlight and has longer days, therefore, it has warmer temperatures

  13. The hemisphere tilted away has shorter days and receives less direct sunlight, and is therefore colder

  14. Skip to last slide… will give out a chart in class

  15. Winter Solstice • Typically 12/21 • Start of winter • Shortest day of the year when the sun follows its lowest and shortest path across the sky.

  16. The sun is over the Tropic of Capricorn (23.5 degrees South) • Points north of the Arctic Circle have 24 hours of darkness, and points south of the Antarctic Circle have 24 hours of daylight

  17. Summer Solstice • Typically June 21 • Start of summer • Longest day of the year

  18. Path of sun in the sky is longer and higher than at any other time • Sun is over the Tropic of Cancer (23.5 degrees North)

  19. The Equinoxes • Vernal (Spring) and Autumnal (Fall) • Typically occur March 21 and September 22

  20. Sun is over the equator • All points all over the world have about 12 hours of daylight and 12 hours of night

  21. Rotation vs. Revolution Rotation Revolution Movement of Earth around the sun Once a year 1 degree of orbit/day Causes seasons and length of day/night Proof: Parallax (apparent movement of the stars) • Movement of Earth around its axis • Once a day • 15 degrees longitude/hour • Causes night and day • Proof: Foucault's Pendulum and Coriolis Effect

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