| Lesson #6: Does Summer Always Come in June?
Overview
In this lesson students will compare the temperatures of cities that have the same latitude, but are in different hemispheres. They will relate this information to the reversal of seasons caused by the tilt of the earth's axis as it revolves around the sun.
Objectives
After completing this unit, students will be able to:
- Explain why seasons are reversed in the northern and southern hemispheres
- Access online data that will demonstrate the season reversal from northern to southern hemisphere
Materials
- Wall map of the world
- Small maps and/or atlases
- Small globe or other sphere to use in revolution simulation
- Table lamp
- Data Collection Sheet
- Weather Learning Logs
Time: One class period
Teacher Preparation
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Activity #1 is designed for younger students who may have the misconception that seasons are explained by how close the earth is to the sun. Because of the tilt of the earth's axis (23.5o) and because of the earth's revolution around the sun, we have seasons. When the part of the earth that we live on is tilted away from the sun, we have winter. The axis of the earth is tilted with respect to the plane of the earth's orbit. The tilt results in the northern regions being pointed toward the sun at some times of the year and away from the sun at others. This change in orientation of the earth with respect to the sun is the cause for changes in the seasons.
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Mark the equator, the poles, and your city on the sphere you will be using for Activity#1. If you don't have a small globe, a tennis ball, a styrofoam ball, or an orange will work well.
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Before beginning Activity #2, bookmark The Weather Underground site. Become familiar with the process of accessing both current weather conditions and historical data for selected cities.
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Have maps and atlases available from which students can choose other pairs of cities to compare.
Procedures
Activity #1 Why do we have seasons?
For this activity, do the following:
- Place a table lamp without the shade on a flat surface.
- Select a student who will walk around the light to simulate the way the earth revolves around the sun.
- Give the student the globe or sphere that you have chosen to represent the earth. Have him point out the spots that you have previously marked on the sphere.
- Remind the students to keep their eyes on the mark that indicates your location.
- Direct the student to walk around the light, making sure that he keeps the ball tilted slightly (23.5o). If the student keeps the point marking your location facing the light, the observers will notice that on one side of the "orbit" the north pole will be pointing toward the sun and on the other side it will be pointing away from the sun.
- The students will conclude that when the sun is shining on the north pole it is summer in the northern hemisphere and winter in the southern hemisphere.
Activity #2 Hemisphere Pairs
For this activity, do the following:
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Distribute data collection sheet.
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Use a wall map to show the locations of the first pair of cities, Melbourne, Australia and Richmond, Virginia.
Ask:
- In what hemisphere is each city located?
- In what country is each city located?
- What do you notice about the latitude of the cities?
- What predictions can you make about the weather that these two cities are experiencing now?
- What kind of weather do you think each city would have in the winter and in the summer?
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Students will record the current temperatures for both cities
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Show the students how to access the historical data for each city.
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As indicated on the data sheet, they will access the temperature for each city on January 1 and July 1 of the previous year.
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Have students compare their results with their predictions.
Ask:
- Can you make a statement comparing the temperature of the two cities?
- Which city has winter in January? July?
- Which city has summer in January? July?
- When do these cities have spring and fall?
- What is the reason for this reversal of seasons?
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They should fill in the data chart with the temperatures of the cities listed and three other pairs of cities that they select. If possible, one of the pairs should be their city and a city in the opposite hemisphere with the same latitude (within 2 degrees). For an online map, go to Infoplease Atlas.
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After they have completed their data sheet, the students will use the information to answer the question "Does Summer Always Come in June?". They should record their answer and explanation in their Weather Learning Log.
Note: Younger students may need help in selecting cities with approximately the same latitude. They do not need to fill in the latitude of their cities. More able students may choose their cities, then check the latitudes at How Far Is It? by typing the name of the city in the "From" section. They can then record the latitudes on the Data Sheet.
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