Academic journal article Science Scope

Sunrise, Sunset: Using Personal Observations to Understand Changing Sun Patterns from an Earth Perspective

Academic journal article Science Scope

Sunrise, Sunset: Using Personal Observations to Understand Changing Sun Patterns from an Earth Perspective

Article excerpt

Misconceptions about Earth-Sun relationships abound (Salierno, Edelson, and Sherin 2005). Many students think that the seasons are caused by Earth's changing distance to the Sun and those who recognize Earth's tilt as the cause often have difficulty explaining this in terms of Sun angle and length of day. Ask a student the location of sunrise and sunset and they are likely to tell you "east" and "west." In reality, the Sun rises due east and sets due west only two days a year. Many students believe that the Sun is directly overhead at noon, but outside of the tropics, a simple observation will prove this thinking incorrect. Recognizing that misconceptions are perniciously difficult to overcome, the lessons presented here attempt to create instances of dissatisfaction with current thought (see Posner et al. 1982) and encourage middle school students to connect with the Sun's changing position from an Earth perspective. By making personal, Earth-bound observations, students can connect their new knowledge in a relevant and exciting way. Through fostering student observations and critical thinking, we hope to provide students with opportunities to draw conclusions from evidence that lead to deeper understanding.

Lesson goals

The goals of these lessons are to help middle school students recognize Sun patterns from an Earth perspective that will advance their understanding of Earth's place in the solar system. Through the use of models and personal observations, these lessons are designed to help students:

* observe that the length of the path of the Sun across the sky, and hence the length of day, changes in a predictable pattern over the course of a year;

* notice that the elevation angle of the Sun in the sky, and hence the Sun angle (the angle between a horizontal plane at the Earth's surface and the incoming sunlight), changes in a predictable pattern over the course of a year; and

* recognize that varying Sun angle and length of day change the intensity and length of exposure to the Sun, thus affecting temperature and causing seasonal change.

Although the Sun rises and sets every day, many students are oblivious to the Sun's change in position. Thus, an additional goal is to engage students with natural phenomena in an authentic and personal way that drives discovery and accommodation of new knowledge.

Engage: Assessing prior knowledge and connecting students with Sun patterns (Day 1)

To assess student knowledge, identify misconceptions, and stimulate thinking, students provide individual written responses to the pre-assessment questions in Figure 1. This important first step identifies students' misconceptions and gaps in knowledge, which serves to focus instruction and ongoing, informal formative assessment. In our experience, we find that many of our students hold common misconceptions, including thinking that the Sun rises due east and sets due west, that it remains at the same angle throughout the year, and that the Earth is closer to the Sun in the summer.

FIGURE 1: Preassessment questions

1. A newly wed couple thinks it will be romantic to watch
the sunset every day for a year. They plan to look out a
small window that faces directly west, What would you
tell them about their method to watch sunsets?

2. Suppose you want to "go green" by installing so far
panels that will be super efficient. You design and
program your panels to follow the Sun, Describe how
your solar panels will move through the day. Will you
adjust the daily movement throughout the year? Explain.

3. A friend wants to know why it is so cold in the winter!
What do you tell him?

After addressing these questions, the lesson continues with students viewing projected photos of sunrises or sunsets, such as those in Figure 2. (Until teachers have collected their own examples of sunrise and sunset photos, Figure 2 can be used for instruction.) By projecting the images individually and sequentially while pointing out reference points, cardinal directions, and dates, the teacher can build anticipation and stimulate questions such as, "Why isn't the Sun rising in the same place every day? …

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