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The Arizona STEM Acceleration Project

Seasonal Changes on Earth

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Seasonal Changes on Earth

A 6th grade STEM lesson

Alex Polydoros

01/27/2024

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Notes for teachers

This lesson takes place in a classroom during one standard class period.
While this lesson is set for students to work in pairs, they can also complete it independently.
There should be an emphasis on identifying patterns within the data.
This lesson is an introduction into the cause of seasonal changes and their patterns that repeat yearly.

List of Materials

For the class:

Globe
Lamp or light bulb

For each pair of students:

Flashlight
Ruler
2 rubber bands
2 pages of graph paper
Pencil
Blank paper
Solar angle and daylight hours data

Notes and Materials:

In this lesson, students will be introduced to the concept of solar angle and how Earth’s tilt on its axis and revolution around the sun are responsible for seasonal changes in temperature, daylight hours, and the sun’s angle in the sky. Globe and lamp or light bulb are optional, but add another visual component to the lesson if needed. Solar angle is a complex topic for this age level, however it is necessary in both understanding seasonal changes, as well as an area’s climate. By using the flashlight, ruler, and piece of paper to draw the differences in how light is spread out when the Sun is at a higher angle in the sky, compared to a lower angle in the sky, students can start to understand both seasonal changes, and why locations at higher or lower latitudes experience more drastic seasonal changes.

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Standards

Science Standards:

6.E1U1.6

Investigate and construct an explanation demonstrating that radiation from the Sun provides energy and is absorbed to warm the Earth’s surface and atmosphere.

6.E2U1.10

Use a model to show how the tilt of Earth’s axis causes variations in the length of the day and gives rise to seasons.

Math Standard:

6.NS.C.8 Solve mathematical problems and problems in real-world context by graphing points in all four quadrants of the coordinate plane. Include use of coordinates and absolute value to find distances between points with the same first coordinate or the same second coordinate.

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Objectives:

Today students will analyze and interpret solar angle and daylight hours data taken from Scottsdale, Arizona in 2023 to identify patterns that coincide with seasonal changes.

Students will also develop an explanation for how these seasonal changes are due to Earth’s tilt on its axis and revolution around the Sun.

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Agenda (60 minutes)

What are seasons? How do seasons look in other locations?
Graphing solar angle and daylight hours.
Identifying a pattern.
Drawing solar angle.
Develop an explanation for seasons.

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How does Earth’s motion affect the amount of daylight hours and the Sun’s angle in the sky?

Record your initial ideas in your science notebook.

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What are seasons?

Do we experiences seasons the same as other states? Other countries? Other continents?

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You have probably observed that the sun seems to move through the sky over the course of a day.

Have you noticed that the sun’s path through the sky also changes from day to day?

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The amount of time the Sun is up also changes from day to day.

In this activity, you will investigate changes in how long the Sun is up and the Sun’s highest position in the sky over the course of a year.

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Patterns

In a group of 2, analyze this data and see if you can identify any patterns.

Graph both sets of data using a line graph.

Hands-On Activity:

Give students adequate time to analyze the data table shown on the right of the slide. Here is a link to a PDF version of the data: Solar Angle and Daylight Hours. This is a perfect opportunity to practice data literacy by asking students what the first thing they should do when looking at a graph (read the title). Explain the data on this graph by discussing what information is included on it. It’s okay if they are unable to identify any initial patterns. By putting it on a graph, they’ll have an easier time recognizing the correlation between the number of daylight hours and solar angle.
Model how to set up the graph paper for students. Have them label the x-axis “Months”. In a group of two students, one should graph the Sun’s highest angle, and the other should graph the number of daylight hours. If you are having students graph independently, they can either make two separate graphs, or use one page of graph paper with the y-axis on the left recording daylight hours and the y-axis on the right corresponding to the sun’s angle. If you choose the latter, have them graph each set of data using a different colored pencil or pen.

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When is the sun….

lowest in the sky?
highest in the sky?

When are the daylight hours….

shortest?
longest?
about 12 hours long?

Class discussion

Once students are done graphing their data, ask them to try to identify any patterns they see. If they are able to identify patterns, encourage them to relate what they see back to what they know about seasonal changes and how we experience seasons in the Northern Hemisphere.
Have a class discussion with students to check for understanding and help students who need more support identify patterns within the data. The data students are graphing was taken from the 21st day of each month, which corresponds with solstices and equinoxes. If your students are unfamiliar with those concepts, this can now also be a good time to introduce them.
Students should be able to identify that in December, the sun was at its lowest angle in the sky and the daylight hours were also the shortest.
Students should be able to identify that in June, the sun was at its highest angle in the sky and the daylight hours were also the longest.
Students should also be able to identify that in March and September, the number of daylight hours were about equal to the number of nighttime hours.

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Discuss with your table group…

What is the relationship between the length of daylight and the sun’s angle?

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Explore - Use a ruler and a flashlight to further explore how changes in solar angle affect distribution of the Sun’s radiant energy.

Use 2 rubber bands to secure a flashlight to a ruler.
Hold the ruler at a 90° angle over a piece of paper.
Draw how the light from the flashlight (the Sun) is dispersed on the piece of paper.

Lower the Sun’s (the flashlight) angle on the paper to about a 30° angle.
Draw how the light from the Sun is dispersed on the piece of paper.
Discuss the similarities and differences between the Sun’s rays at both angles.

Hands-On Activity:

Using two rubber bands, students should secure a flashlight to the end of a ruler. It should be secured so that there are about 6 inches of ruler left below the bulb of the flashlight.
Students will start by observing how a direct, higher solar angle concentrates radiant energy on a location. Discuss that this angle is higher than what would be experienced in Arizona, as the highest angle shown in the data table is 65.74°. You can discuss that locations closer to the equator experience a more direct, near 90°, and how this results in no seasonal changes.
Students should be able to identify that, when the Sun’s angle is lower, the radiant energy hitting Earth’s surface is less-concentrated and more spread out. The energy received is not less, just less-concentrated.

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Flashlight set-up

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Demonstrate solar angle.

Observe the Sun’s angle as Earth continues on its orbit around the course of a year.

Class Demonstration

If students need another visual aid, you can now demonstrate how, as Earth revolves around the Sun, that different hemispheres experience seasons differently depending on the orbital position of Earth and the 23.5° axial tilt.
Use a globe to model Earth. Ensure that the globe is tilted in respect to Earth’s 23.5° axial tilt.
Hold a lamp or light bulb pointed towards the globe. I demonstrate first the season that we’re currently experiencing when this lesson is taught. In the winter months, I’ll ensure that the globe is tilted in a way that the Southern Hemisphere is experience summer (tilted toward the Sun.) Have students identify the angle at which the Sun is hitting the globe. Confirm that during this orbital position, the Sun is more directly hitting the Southern Hemisphere, resulting in a higher solar angle and longer daylight hours (summer). The Northern Hemisphere is tilted away from the Sun, resulting in a lower solar angle, shorter daylight hours, and winter.
This can also be a time to point out the North and South Pole and describe their angle. When the Southern Hemisphere is experiencing summer, locations around the South Pole are experiencing extremely long daylight hours. Alternatively, locations closer to the North Pole are experiencing very few daylight hours.

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Assessment

Revisit the guiding question… “How does Earth’s motion affect the amount of daylight hours and the Sun’s angle in the sky?”

Share your thoughts with your partner. Be prepared to share with the class.

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Differentiation

Students who need additional support can create a model on a mini-whiteboard or in their notebook with teacher support of the orbital path and tilt of Earth.

Remediation

Extension/Enrichment

Students can research the solar angle and daylight hours of a Southern Hemisphere city. Scottsdale has a latitude of 33°N. Melbourne, Australia has a latitude of 37°S.
Students can graph data for daylight hours and sun’s highest angle for Melbourne and compare their graphs.