Reasons for Seasons
Exploring the Astronomy of Spring (a mini-unit)

Watching the wave of spring sweep northward is at the heart of Journey North. Students see seasonal changes all around them, yet these changes are all driven by one underlying factor: changes in available sunlight. This includes:

  • the amount of available sunlight (called day length 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.
Lesson Overview
Exploring Hourly Shadows and Sunlight This slideshow inspires students to investigate shadows and sunlight outdoors over the course of a day. Students begin to grasp what happens as locations on earth move into and out of the sun's light each day.
Exploring Seasonal Shadows and Sunlight Students measure shadows from fall through spring. They begin to understand the relationship of sunlight, shadows, and seasons. This will help them later grasp how the Earth's tilt on its axis influences these phenomena.
Following the Sun for a Day Students create a simple model of the Earth and sun as seen from space. They use it to explore the sun's apparent movement across the sky. They begin to understand that the Earth's rotation toward the east causes the sun to appear to move west each day.
Following the Sun Through the Year Students create a simple model of the Earth and Sun as seen from space. They use it to explore the apparent changes in the sun's angle (height above the horizon) throughout a year. They begin to make connections between the sun's angle in the sky, temperatures, and the seasons.
Modeling the Seasons Students create 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.
Heating Up: Direct and Indirect Sunlight By conducting simulations, students explore the effects of direct and indirect sunlight on heating of the Earth.
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.

Note: To fully grasp what causes seasons, your students need a variety of opportunities over time to explore light, shadows, and Earth-Sun models. These activities, which require few materials, offer some basic strategies for getting started. Visit the links below to dig deeper and find inquiries designed for different grade levels.

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.

Choose from these tasks and tools to document student understanding of key concepts in this mini-unit.