Reasons for Seasons
Exploring the Astronomy of the Seasons
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— Mini-Unit

To fully grasp what causes seasons, students need a variety of opportunities over time to explore light, shadows, and Earth-Sun models. The five activities in this mini-unit require few materials and offer some basic strategies for exploration. You can use them sequentially or individually to reinforce or lay the groundwork for your students' online investigations of seasonal change.

Watching seasonal change is at the heart of Journey North. Students observe evidence of seasonal change all around them, yet all of these changes are driven by one underlying factor: changes in available sunlight. This includes:

  • the amount of available sunlight (called daylength or photoperiod)
  • the sun's intensity (related to the angle at which it strikes the Earth).

Mini-Unit Objectives
These background lessons are designed to reinforce or lay the groundwork for your students' Journey North studies. The lessons can be used sequentially or individually. After this series of lessons, students in grades 4-8 should be able to:

  • Model the tilt of the Earth as it orbits the Sun.
  • Understand the meaning and characteristics of solstices and equinoxes.
  • Understand that sunlight hits the Earth at different angles at different locations over the course of a year and that this affects temperatures.
  • Explain what causes seasonal changes.
Activity Overview
1. Exploring Shadows and Sunlight By measuring changes in shadows over time, students notice daily and seasonal patterns.
2. Following the Sun 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.
3. Modeling the Seasons Students explore a model of the Earth’s daily rotation and annual revolution around the sun; they try to puzzle out at which point each season occurs in their part of the world.
4. Heating Up: Direct and Indirect Sunlight By conducting simulations, students explore the effects of direct and indirect sunlight on heating of the Earth.
5. Sunrise, Sunset, and Seasons Students track photoperiod (daylight hours) over time, predict how daylight will change during different seasons, and use this to enhance their understanding of seasonal change.

Laying the Groundwork for This Unit

Younger Students

  • Ask students to create a list of things they see, do, and feel during different seasons. Ask, How do these things change from season to season? Do any of these relate to the environment (e.g., temperature changes)? Describe how. (E.g., You can ice skate because it’s cold enough for water to freeze; robins come back because it’s warmer.) What do you think causes these changes?
  • Generate list of questions raised by this exercise and use it as a springboard for some of this mini-unit's activities.

Older Students

  • Ask students to try to characterize the different seasons by discussing weather, appearance of living things, human activities, and so on. Ask, What do you think causes each of these changes?
  • Invite students to share what they know about the reasons for seasons.
  • Generate a class list of things they’re unsure of and questions they have. Use these as a springboard for some this mini-unit's activities.

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