CTS Guide: Seasons and Seasonal Patterns in the Sky, pp 242-243- Section IV Research Summaries

The Reason for Seasons

• A review of 41 research studies on people’s understanding of the seasons (Sneider, Bar, and Kavanagh 2011) found that although understanding of seasons tended to increase with age, misconceptions were widespread even among college students and educated adults. For example, many people learn in school that seasons are due to Earth’s tilt, but have the misconception that the tilt causes Earth to be closer to the Sun in summer. (In fact Earth is closest to the Sun in January, which is winter in the Northern Hemisphere.) The review article suggests a sequence of instruction beginning in elementary school, leading to full understanding of seasons in high school. One of the suggestions is to have students imagine what would happen if Earth had no tilt. Day and night would always be 12 hours long, and although there would be climate differences at different latitudes, there would be no variation in climate during the year. However, the phenomenon of different constellations during different seasons would be the same because that is a consequence of Earth’s annual orbit around the Sun and is unrelated to tilt. Other effective approaches include having students observe changes in the path of the Sun during the year; teaching about seasonal changes at different latitudes, including the Southern Hemisphere; testing common misconceptions using physical models; and using 3-D modeling software.

• A number of researchers suspected that common textbook illustrations of Earth’s orbit around the Sun showing an elongated ellipse to indicate perspective misled students about the changing distance from the Sun. This expectation turned out to be wrong, at least for ninth-grade students. However, the researcher noted that since some students could develop that misconception, teachers should point out that the elongated ellipse in the diagram is meant to show perspective, and that in fact the orbit is nearly circular (Lee 2010).

• Students of all ages (including college students and adults) have difficulty understanding what causes the seasons. Many students up through preservice believe that winter is colder than summer because the Earth is farther from the Sun in the winter. This belief persisted even after instruction in Earth science (AAAS 2009).

• Some students confuse Earth’s daily rotation with its yearly revolution around the Sun (Salierno, Edleson, and Sherin 2005). For example, they believe that the side of Earth not facing the Sun experiences winter.

• Galili and Lavrik (1998) found that students’ ideas about how light travels may interfere with their understanding of the seasons.

• As part of an evaluation of a new high school course on astronomy, Sadler (1998) tested 1,250 high school students who had taken the course, which included instruction on the reasons for the seasons. One of the questions on the test was as follows: “The main reason for its being hotter in summer than winter is: (a) The Earth’s distance from the Sun changes; (b) The Sun is higher in the sky; (c) The distance between the northern hemisphere and the Sun changes; (d) Ocean currents carry warm water north; and (e) An increase occurs in ‘greenhouse’ gases.” Sadler found that most students who did poorly on the test overall chose the common misconception that Earth’s distance from the Sun changes during the year. Most students who did moderately well chose a different misconception, that the distance between the Northern Hemisphere and the Sun changes, indicating that they understood that the tilt was somehow related to seasons; but they misunderstood how the tilt caused the seasonal variation in temperature. Only the students who did very well on the test overall chose the correct answer: “(b) The Sun is higher in the sky.” Sadler concluded that these misconceptions should not be considered failures, but rather stepping stones toward a full scientific understanding.

• Baxter (1989) noted age-related trends in children’s alternative conceptions related to seasons. The most common conception in children up through the age of 16 was that the Sun is farther away in the winter. This was consistently prevalent across ages and particularly pervasive in the 9–12 age range. Up to age 10, a small number of students think changes in plants cause the seasons. This number increases between the ages of 10 and 12. A small number of students up to ages 9 and 10 think winter clouds stop the heat from the Sun. This idea increases slightly between ages 10 and 14. Up until age 12, some students think the Sun moves to the other side of Earth. By age 12, this idea seems to go away.

• Studies by Sadler (1987) and Vosniadou (1991) show that students may not be able to understand an explanation of the seasons until they can reasonably understand the relative size, motion, and distance of the Sun and Earth.

Seasonal Changes in the Sky

• Plummer (2008) interviewed 20 students in each of grades 1, 3, and 8. While she found a general trend toward higher levels
  of understanding among the older students, students at each grade level held misconceptions 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. However, she did find that students were able to learn about the Sun’s changing path in the sky during the year with the help of a small planetarium.

• Willard and Roseman (2007) relied on Benchmarks and findings from other studies to propose a learning progression for the seasons that required two essential prerequisites: (1) the link between sunlight and temperature and (2) an accurate understanding of how the Earth moves with respect to the Sun. Understanding why we see different constellations in different seasons can help students understand the Earth’s annual motion around the Sun.