Sun

• Earth's orbit


  Elliptical, completes one revolution around the sun every 365 days, 6 hours, and 8 minutes
• Revolution


  Movement of the Earth around the sun, due to the Earth's axis being tilted approximately 23.5 degrees
• Rotation


  One full rotation of the Earth equals one day, Earth rotates counterclockwise
• Direct rays

  Light rays that are hitting the earth at 90 degrees, receiving more energy
• Indirect rays


  Light rays that hit the earth at an angle, receiving less energy
• The equator is always hit by direct rays of the sun, which is why it is always warm there
• The poles are always being hit by indirect rays, which is why it is cold there
• Seasons


  1. Spring

  2. Summer

  3. Autumn

  4. Winter
• Spring


  • Starts when the day and night are the same length on March 20, weather gets warmer and sunnier, tree and plants start to grow, many animals have their babies
• Summer


  • Begins on the longest day of the year, usually the warmest and sunniest time of the year, fruit grows on trees and plants, young animals grow bigger and stronger
• Autumn

  • Starts when the day and night are the same length again on September 21, leaves change color and fall from the trees, some animals collect food before winter comes
• Winter


  • Begins on the shortest day of the year, weather is colder and there is lots of snow in some places, plants and trees stop growing, some animals hibernate
• Earth has seasons because its axis is tilted
• Solstices and Equinoxes


  1. December 21/22 (Winter Solstice)

  2. March 20/21 (Spring Equinox)

  3. June 21/22 (Summer Solstice)

  4. September 22/23 (Autumn Equinox)
• Subsolar point


  Occurs on the equinoxes, when the sun is directly overhead at the equator
• Perihelion


  When the Earth is nearest to the Sun, happens around January 3rd
• Aphelion


  When the Earth is farthest from the Sun, happens around July 4th
• Direct rays


  Sun's rays hit the ground at 90 degrees, each square meter receives more solar energy
• Oblique rays


  Sun's rays come in at an angle, each square meter receives less solar energy
• Latitude


  Measurement of distance north or south of the Equator, increases from 0 to 90 degrees
• Different parts of the Earth receive different amounts of solar radiation due to the spherical shape of the Earth