The relationship between the Earth and the Sun governs students’ daily existence on this planet, from the time they wake and go to sleep to the clothes they choose to wear in the morning. Being able to envision the Earth and the Sun in space is key to understanding Earth’s place in the Universe and fundamental ideas as why we experience night and day as well as seasons. The elementary grades are when three fundamental observations and ideas about the Earth-Sun system are developed: that the Sun follows a predictable path from sunrise to sunset, that the Sun is highest in the sky around (but rarely exactly) at noon, and that when the Sun is not in the sky it is somewhere below the horizon, on the other side of the ball-shaped Earth. The probe Sunrise to Sunset (Figure 1) is used to elicit students’ initial ideas about the apparent movement of the Sun and reveal where students think the Sun rises and sets and the path it takes during the day (Keeley and Sneider 2012).

The best answer to this probe is from Avi, “I think the Sun rises on one side and sets on the other.” The Sun’s apparent motion across the sky during the day is arc-like, as shown in Avi’s drawing. The Sun rises along the eastern horizon, appears to travel across the entire sky, and sets along the western horizon. Viewed from the Northern Hemisphere, facing south, it seems like the Sun is moving across the sky in a left-to-right direction. At around noon (which is the midpoint between sunrise and sunset) the Sun appears to be at its highest point in the sky. However, the Sun only appears to move in an arc across the sky. It is the Earth’s rotation that is responsible for this visual effect.

Research has shown that children come to the classroom with ideas about the relationship between the Earth and Sun. Plummer (2008) interviewed 20 students in each of grades 1, 3, and 8. Although she found a general trend toward higher levels of understanding among the older students, students at each grade level had misunderstandings about how the Sun appeared to move through the sky during the day and how the Sun’s path across the sky changed with the seasons. Many of the children at all ages thought that the Sun was directly overhead at noon every day, even though the Sun was never overhead at noon at the latitude where the children lived. Furthermore, there was no significant difference between third-grade students’ and eighth- grade students’ understanding of the Sun’s apparent motions.

Another study by Plummer and Krajcik (2010) found that children as young as first grade knew that the Sun gets higher in the sky during the day and lower in the sky during the evening, although most were not able to accurately describe the Sun’s path. Some of the students envisioned the Sun going up and then down on the same side of the sky. Other students thought the Sun stopped moving in the sky during the day. However, after a planetarium program about the Sun’s path, 86% of first- and second-grade students were able to describe the Sun’s path as rising on one side of the sky, following a continuous arc, and setting on the other side of the sky.

For students who chose Jessica’s answer and think that the Sun rises vertically above the horizon in the morning and then comes back down toward evening, be aware that these students might be bound by the language we use. The words sunup and sundown or sunrise and sunset imply that the Sun goes up and down in the sky. It is particularly important that these students have an opportunity to observe the position of the Sun throughout the day and how it moves in a smooth continuous arc from one side of the sky to the other. Safety note: Students should never look directly at the Sun. The best way to observe the Sun’s motion is to have children mark the position of a fixed object, like a flagpole. It is important to explicitly point out that the shadow marks the direction opposite the Sun. When the Sun is highest in the sky, the shadow will be the shortest.

Additional probes to use as bundle for the three fundamental elementary science ideas related to the Sun-Earth system include No Shadow, to reveal whether students understand that the Sun is never directly overhead at noon from most places on Earth; What’s Moving, to reveal whether students understand the Earth moves around the Sun; and Where Did the Sun Go, to reveal where students think the Sun is in relation to Earth during nighttime (Keeley and Sneider 2012). Taken together these probes provide an opportunity for students think about, investigate, model, and explain the phenomenon of the Sun’s apparent motion across the daytime sky and use the crosscutting concept of patterns to develop an understanding of the relationship between the Earth and the Sun before moving further out into the universe. ●

Page Keeley (pagekeeley@gmail.com) is a science education consultant and the author of the Uncovering Student Ideas in Science series (http://uncoveringstudentideas.org).