Seasons Gizmo

Questions to Ponder

Both New Zealand and Argentina are in the Southern Hemisphere (south of the equator).

1. What time of year would you plan a ski vacation in New Zealand?

2. What time of year would you visit the beaches of Argentina? 

Gizmo Warm-up

Seasons in the Southern Hemisphere are different from seasons in the Northern Hemisphere (north of the equator.) Using the Seasons in 3D Gizmo, you will discover what causes the seasons and learn why seasons are different in each hemisphere.

To begin, move the Simulation speed slider all the way to the right. Click Play and observe the SIMULATION pane.

1. Describe Earth’s movements: Earth revolves around the Sun and rotates on its axis. On the SIMULATION pane, the axis is represented by a red line.

2. Click Reset, and then click Play again. Look at the side view of Earth at the bottom of the SIMULATION pane.

3. What do you notice about Earth’s axis as Earth revolves around the Sun?

4. When is the Northern Hemisphere tilted toward the Sun?  When is the Southern Hemisphere tilted toward the Sun? 

Activity A: Height of the Sun

Get the Gizmo ready:

• Click Reset.

Question: How do seasons compare in the Northern and Southern Hemispheres?

1. Compare: A location’s latitude gives its distance north or south of the equator. On the DESCRIPTION pane, set the Latitude to 45.0°N.   Next, drag the slider at the bottom of the DESCRIPTION pane to set the date to June 21.  Is the Northern Hemisphere tilted toward or away from the Sun?  How much light is falling on the Northern Hemisphere compared to the Southern Hemisphere?  Change the date to December 21. On this date, which hemisphere is receiving more sunlight? 

2. Observe: Move the Simulation speed slider all the way to the left. Select the 2D VIEW tab and make sure Facing south is selected.  Using the date slider at the bottom of the Gizmo, set the date to June 21. Click Play. Click Pause ( ) when the Sun reaches its highest point in the sky. Draw and label that position in the picture at right. Then, find the Sun’s highest point in the sky for December 21, and draw and label that position.

3. Analyze: On which date was the noon Sun higher in the sky? This date is the summer solstice in the Northern Hemisphere. The date on which the noon sun is lowest is the winter solstice.

4. Explain: How does the orientation of Earth’s axis relate to the position of the Sun in the sky?

5. Predict: On the DESCRIPTION pane, set the Latitude to -45° (45° S). For this latitude, on which date do you expect the noon Sun to be highest? : June 21 or December 21

6. Observe: Select the 2D VIEW tab and select Facing north.  Set the date to June 21, and click Play. Click Pause when the Sun reaches its highest point in the sky.  Diagram that position.  Then, find the Sun’s highest point in the sky for December 21, and diagram that position.

7. Analyze: On which date was the noon Sun higher in the sky? 

8. Explain: Why were your results for the Southern Hemisphere opposite of what you found for the Northern Hemisphere?

9. Infer: Based on the height of the Sun in the sky, at what time of year is it summer in the Southern Hemisphere? When is it winter in the Southern Hemisphere? Explain.

Activity B: Solar intensity

Get the Gizmo ready:

• Click Reset and make sure the Simulation speed slider is all the way to the left.

Question: Why is it warmer in summer than in winter?

1. Describe: Look up the latitude of your city or town. Set the Latitude to this value.

2. Gather Data: What town do you live in, and what is its latitude? What is the temperature of a typical summer day in your town?  What is the temperature of a typical winter day in your town?

3. Observe: Select the GRAPH tab. The Day graph shows solar intensity, or the amount of solar energy striking a location in an hour. Set the date to March 21, which is the spring equinox in the Northern Hemisphere. Click Play, and then Pause before 24 hours pass.

4. Gather Data: At what time of day is solar intensity greatest?  What is the solar intensity at night?  Why do you think the solar intensity follows this pattern? 

5. Gather data: Record the solar intensity (using the Solar Intensity Data Table found below) at noon on March 21. Then record the times of  sunrise (solar intensity begins to rise) and sunset (solar intensity returns to zero). Based on these times, calculate the hours of daylight. Repeat for each solstice and equinox.

6. Analyze: Use the table to compare the hours of daylight on the equinoxes (March 21 and September 23) and solstices (June 21 and December 21).  What is the longest day of the year? _______________ Shortest? ______________ What do you think the word equinox means? _______________________________

7. Explain: Why is the noon solar intensity greater on the summer solstice than on the winter solstice?

8. Observe: Click Reset and set the Simulation speed to its highest value. On the GRAPH tab, select the Year graph. Click Play. After a year has passed, sketch the resulting graphs at right.  What factors are responsible for the changes you see in the Solar energy graph?

9. Summarize: Seasonal changes are related to the length of a day and the height of the Sun in the sky. Describe how these two factors change throughout a year, and how this relates to the seasonal changes you observe in your home town.

Back to Teams

1. How does the amount of solar energy striking the Northern Hemisphere change over the course of the year? 

2. What causes these changes?

3. Why are days longer in the summer and shorter in the winter?

4. Why is solar intensity greater in the summer than in the winter?

5. Why does the Sun rise higher in the sky during the summer than in the winter?

6. What causes the seasons? Do you think Earth would have seasons if its axis wasn’t tilted?

• The Solar Panels at Colonel Richardson Middle School are all set at an angle.  Explain why they are set up this way.

• Would all solar panels around the world be set up the same way, at the same angle?  Why or why not?