Outline of concepts to be presented

Expanded description: In this lab, students chart the changing path of the sun as they explore the "reasons for the seasons." Each student creates a graph showing the path of the sun across the planetarium sky and the duration of daylight on both equinoxes and solstices. If you make this graph in the classroom, more time can be devoted to making observations and comparing locations. Modeling demonstrations are used to show why the changes in the sun's path occur. The main goals in the lab are to destroy the distance misconception (tactfully), and to help make a connection between the height of the sun in the sky, and the season.

Sequence

  • Observe the sun's apparent path across the sky for all four seasons here in Madison (recording on graph?). The students are looking for patterns and making predictions while they are making the observations. The are also noting the differences in the length of day throughout the year. The order of the seasons we generally follow is: Autumnal Equinox, Winter Solstice, Vernal (spring) Equinox, and Summer Solstice.
  • Summarize the observations for Madison.
  • As time allows, reset the planetarium projector for Christ Church, New Zealand, and Prudoe Bay, Alaska. Observe a "Summer Solstice" day in these locations. Discuss.
  • Use a Sun-Earth model to discuss the fact that the hemispheres have opposite seasons. Apply this concept to the distance misconception; and include the fact that the Earth is closest to the Sun in January, and that the variation in distance is only about 3%.
  • Use a Sun-Earth model to show how the tilt of the Earth's axis causes the changes they've seen in the height of the sun and length of the day.

General Concepts

  • Altitude and Azimuth: a way of describing positions in our local sky.
  • Changes in length of day throughout the year.
  • Changes in the sun's apparent path across the sky throughout the year.
  • The tilt of the Earth's axis as it relates to the cause of seasonal change.

Connecting to the Classroom

The seasons lab works well as an introduction to learning the causes of seasonal change. Some things can be done before and/or after your visit to maximize the time in the planetarium. However, no teaching of the causes of the seasons is required or even recommended before this lab.

Pre-Visit Activities you might consider doing in the classroom :

  • If you only had one day to prepare before your visit:
    Some of the vocabulary that we use in the lab would be helpful to cover ahead of time. (See vocabulary list below.) It would be especially helpful for the students to know what equinox and solstice means, and approximate dates for the beginning of each season.
  • Observe the sun's position in the sky:
    Although most middle school students to adults could "tell" you that the sun is not always in the same place in the sky throughout the day, many people have never really made intentional observations of this for themselves. It is recommended that the students go out at the beginning, middle, and of the day and observe the sun's position in the sky. Safety note: never look directly at the sun! You can make these observations by placing your hand over the sun in the sky. If possible, make these observations on more than one day in a week. The ideal situation would be for students to repeat these observations in more than one season. If you do this, the students should record their observations.
  • Discuss seasonal temperature changes:
    From a geography point of view, discuss seasonal variations in temperatures here in Wisconsin, and compare to other locations on the Earth. World Climate
  • Record the Sun's apparent path on a grid:
    To save time in the planetarium (which can then be devoted to making more observations and exploring the Sun-Earth connections), some teachers choose to record the sun's path during each season in the classroom or computer lab. This is done by plotting the sun's rising point (altitude and azimuth), noon position, and setting point: then connecting with a smooth curve and labeling the line. Do this for the Autumnal Equinox, Winter Solstice, Vernal (spring) Equinox, and Summer Solstice. Completion of this grid could be done before, during, or after your visit. Some teachers choose to have their students access this information through planetarium-like programs such as Voyager, TheSky, or Starry Night Pro in their computer lab. This data can also be obtained at: US Naval Observatory

Post-Visit Activities you might consider doing in the classroom :

  • Show the connection between sun angle and heating
    Use a flashlight to shine light on a light-colored table or other horizontal surface in a dark room to show how the angle of the light source effects heating. The flashlight represents the sun, and the table represents the surface of the Earth. Tie a string around a flashlight to maintain a constant distance between the light source and the table. Vary the angle of the "sun" to show how the light as seen on the table varies in intensity. When the "sun" is at a low angle, the light on the table seems less intense (less bright) and students will notice that it is spread out over a larger area. Apply this concept to the height of the sun during the different seasons.
  • Record the Sun's apparent path on a grid:
    To save time in the planetarium (which can then be devoted to making more observations and exploring the Sun-Earth connections), some teachers choose to record the sun's path during each season in the classroom or computer lab. This is done by plotting the sun's rising point (altitude and azimuth), noon position, and setting point: then connecting with a smooth curve and labeling the line. Do this for the Autumnal Equinox, Winter Solstice, Vernal (spring) Equinox, and Summer Solstice. Completion of this grid could be done before, during, or after your visit. Some teachers choose to have their students access this information through planetarium-like programs such as Voyager, TheSky, or Starry Night Pro in their computer lab. This data can also be obtained at: US Naval Observatory
  • Discuss the connection between day length and heating.
  • Discuss what "seasons" on the Earth would be like if the Earth was not tilted, or if it was tilted at a greater angle.

Vocabulary: some of the words the students will likely encounter

  • altitude
  • azimuth
  • latitude
  • meridian (possibly)
  • hemisphere
  • orbit
  • axis
  • solstice
  • equinox