Reasons for Seasons
Exploring the Astronomy of the Seasons
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Activity 2: Following the Sun
(Activity #2 of Reasons for Seasons)

Overview: Students use a simple model of the Earth and Sun as seen from space to explore the sun's apparent movement across the sky over the course of a day and year. They consider the apparent direction of movement and changes in the sun's angle.

Preparation: Plan the first part of this investigation for a sunny, dry day. If possible, launch it in the fall.

Laying the Groundwork
Invite students to imagine they are far out in space and can see the Earth and our sun. Ask, What would you expect to see happening and why? Make four different drawings, to show what you'd see during a day or year. Once students have completed this, ask, What questions do you have? Save these for students to revisit during and after this activity.



Click to enlarge.

Time
1-2 periods and then a few minutes each day and month

Materials
clear 2-quart bowl, large sheet of white paper taped to a piece of cardboard or other rigid item, sharp pencil, erasable marker, compass, crayons or colored pencils

Exploration:

  1. Make an X in the center of the paper to represent our Earth.
  2. Take all the materials outside. Find a level surface for the paper. Make sure the location receives sunlight throughout the day.
  3. Place the bowl upside down on the paper and ask students to imagine it's our atmosphere. Mark an x on the center of the bottom of the bowl with the overhead marker. Make sure the x on the paper is lined up under the x in the center of the bowl. Trace the edge of the bowl onto the paper to make it easier to line up.
  4. Have students use a compass to determine North for your location. Once they've reached consensus, they should mark North on the paper and the bowl.
  5. Each hour, have a student touch the side of the clear bowl with the tip of the pencil so the shadow of the pencil's tip falls on the X on the paper. Have a partner make a dot on that spot with the marker. (They can put a number beside each dot to recall the order in which they made observations.) After each dot goes on, ask students, Where do you predict the next dot will be? Explain your thinking. Which direction does the sun appear to be moving?
    Note: To get accurate results, the bowl must sit in the same location and be lined up in the same way for each hourly (and monthly reading).
  6. Repeat this activity each month Use one color overhead marker from September through December and another color from January through June. If this is done on or about the 20th of each month students will see what happens on the fall and spring equinox and the winter solstice. Their marks will indicate the changes in the angle of the sun throughout the year.

What to Expect
Over the course of a day, the sun will appear to be moving west. But students' earlier explorations should have revealed that the sun does not move. Rather, it is the earth's rotation counterclockwise (toward the east) that makes the sun appear to move west.

As students mark the sun's apparent movement throughout the year, they'll find that it appears lowest in the sky (the greatest angle) on the winter solstice (because of the Earth's tilt) and highest in the sky (most direct) on the summer solstice. It is somewhere between the two on the equinoxes.

Making Connections — Discussion and Journaling Questions

  • What patterns did you notice over the course of the day (year)?
  • How would you explain them?
  • What general statement(s) could you make about the movements of the sun and earth?
  • What questions do you still have?
  • How does this help you better understand the seasons?
  • If you noticed that the sun appeared higher in the sky than it was a month ago, which seasons could it not be? Explain your thinking. (Fall)

Assessment
After making daily and seasonal markings, ask students to revise the drawings they made during Laying the Groundwork. They can either create new ones or use another color to make changes. Their responses to the discussion and journaling questions along with the changes in their drawings should reveal an enhanced understanding of the daily and seasonal Sun-Earth relationship.

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