Misconceptions in Astronomy in WA High School students (in preparation)

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1 Misconceptions in Astronomy in WA High School students (in preparation) Michael Todd Department of Imaging and Applied Physics, Curtin University of Technology The purpose of this study was to examine the change in students understanding of phenomena such as phases of the Moon, the seasons, and the relative motions of the Earth, Moon and stars across different years of high school in Western Australia and to identify the proportions of students who hold scientific views as well as identifying the most popular non-scientific views and comparing results with similar, earlier studies. Introduction It has long been accepted that children construct their own beliefs and knowledge from observation and experience of the world around them before they enter formal education. It has also been established that their cognitive and analytical abilities develop as they grow and mature, and that some of their earlier beliefs will be discarded and replaced with new beliefs as a consequence. The role of the educator is to become a part of this process and enable the replacement of an incorrect belief with the correct scientific view by providing the learner with the information and experiences necessary to this development. It is apparent that the success of this process has always been limited numerous studies have been conducted to evaluate students knowledge and to identify misconceptions. Of the studies which have examined Earth Science and Astronomy most have focused on student understandings with the remainder looking at teacher understandings. Such studies all show that in most areas of astronomy the majority of students, and many teachers, hold non-scientific views. Some researchers have investigated primary school children s understanding of familiar astronomical events (Sharp, 1996; Stahly, Krockover, & Shepardson, 1999) while others investigated the beliefs of children across both primary and secondary levels of education (Baxter, 1989; Dunlop, 2000). While the studies which examined the beliefs of students in secondary education indicated some further change in student understanding after Grade 6 no research was found to indicate instances of significant change. Little difference was also found between studies conducted in different countries including Australia, New Zealand, Britain and the United States. The particular phenomena of phases of the moon, the seasons, and the relative motions of the Earth, Moon and stars were selected for study as these topics are included in the standard high school curriculum in Western Australian schools, and the concepts are explained in science textbooks such as Fundamentals of Science (Anderton, 1990). The Earth, Sun and Moon While it may be argued that most people accept a Sun-centred model of the Solar System it must be remembered that this knowledge is not intuitive as it cannot be simply inferred from the observed motions of the Sun and Moon. The simplest

2 assumption is that the Sun and Moon move across the sky, and learning that the Earth is spherical easily leads to the geocentric belief that the Sun and Moon both orbit the Earth. Expansion of knowledge to include the Solar System and diagrams or models of the planets orbiting the Sun with the rotation of Earth to explain day and night demonstrates a simple and appealing concept which is usually readily adopted by students. Jones et al. (1987, p. 49) showed a significant change in student views moving from an Earth-centred cosmic model to a Sun-centred model between Grade 3 and Grade 6 of school; 25% of Grade 3 students proposed a Sun-centred model compared with 62.5% of Grade 6 students. Similarly, Sharp (1996, p. 708) reported that 55% of Grade 6 students proposed a scientific, Sun-centred model. Baxter (1989, p. 508) and Dunlop (2000, p. 194) related similar results. What becomes apparent when this concept is probed further is that while this belief is widespread at a macroscopic level, many students still fundamentally believe that the Sun moves across the sky rather than understanding that they are on a rotating Earth since they can observe the Sun to rise in the east and move across the sky to set in the west. Phases of the Moon Most people can relate that the Moon changes shape or phase over a period of time however there is some uncertainty over the period and regularity of the change, and a widespread notion that the shape of the Moon is a result of some thing obscuring part of the Moon or casting a shadow on its surface. Baxter (1989, p. 510) found that the notion that the Earth casts a shadow on the Moon was the dominant view among students aged 9 to 16. A review of research literature by Stahly et al. (1999, p. 160) found that this eclipse explanation was the most common misconception held for the cause of lunar phases. Sharp (1996, p. 708) found that 40% of Grade 6 students gave a scientific account for the cause of the phases of the Moon, and that while only 5% considered the eclipse explanation 24% believed phases were caused by clouds casting a shadow on the Moon. 10% of the students held the view that the Moon went through a complete cycle on a daily basis. Dunlop (2000, p. 201) reported that 13% of students held the eclipse view before teaching and that 12% still held this view after teaching, suggesting that misleading diagrams in textbooks and not-to-scale models of the Earth, Moon and Sun used in teaching lead to difficulty in students accepting the correct explanation of phases. Taylor (1996, p. 39) states Two decades of science education research have amply demonstrated that many students hold non-scientific views about the phases of the Moon even after having been taught the scientific view. This is true even of university graduates and teachers. Studies examining primary teachers understandings support this view. A study by Parker & Heywood (1998, p. 512) found that 47% of primary teachers held alternative views and that the eclipse view comprised 96% of the alternative views.

3 Earlier studies by Callison & Wright (1993), Dai & Capie (1990), and Schoon (1995) (as cited in Trundle, Atwood, & Christopher, 2002, p. 634) indicated that between 80%-95% of pre-service primary teachers did not understand the cause of the phases of the Moon. Pre-service primary teachers conceptions of moon phases before and after instruction were studied by Trundle et al. (2002, p. 648), finding that 5% of participants could give a scientific explanation for the phases of the Moon before receiving instruction. Another finding was that 61.4% of all participants did not understand that the Moon revolves around the Earth and 93% did not know that the Sun always illuminates half of the Moon. A diagnostic test administered to students taking Astronomy 101 at Curtin University of Technology in February 2008 showed that 73% of participants could not explain that a crescent moon was caused by the relative positions of the Earth, Moon and Sun (C. Hotan, personal communication, May 12, 2008). From these data it can be inferred that students knowledge that the Earth is roughly spherical and observation of the shape of a crescent moon leads them to construct the belief that at times the Moon is partially shadowed by the Earth to produce those phases. It is clear that instruction on the cause of the phases of the Moon as part of most students formal education fails to convince them of the scientific explanation. Seasons Students apparent acceptance that the Earth rotates to give us day and night and revolves about the Sun each year does not automatically translate to an understanding of the seasons. While students may be able to relate these facts and state that we experience the four seasons during each year the literature generally agrees that seasons are the least well understood topic and that the majority of students have difficulty explaining the cause of seasons. Sharp (1996, p. 708) related that only 19% of students could give a scientific explanation for the cause of seasons. Similarly Dunlop (2000, p. 201) reported 25% of students surveyed could explain seasons. Baxter (1989, p. 511) also showed that the minority of students could explain seasons in relation to the tilt of Earth s axis and revolution about the Sun. Similar studies involving preservice primary teachers (Atwood & Atwood, 1996, p. 556; Parker & Heywood, 1998, p. 510) reported that 2% and 9.7% respectively could provide scientific explanations for the cause of seasons although the study by Atwood & Atwood noted that 78% of participants identified that Earth s axis is tilted. The dominant alternative concept for the cause of seasons was that the distance from the Sun to the Earth changed during the year; when the Earth is closer to the Sun we experience summer and when the Earth is farther we experience winter. The trend indicated by the different studies was that younger students expressed a simple changing Earth-Sun distance while older students often expressed an elliptical orbit concept. Constructive learning theory suggests that students integrated knowledge about orbits into earlier beliefs involving changing Earth-Sun distances. Alternatively students may have constructed this view of elliptical orbits from diagrams and descriptions in textbooks which often utilise perspective drawings of orbits with the result that

4 Earth s orbit appears highly elliptical rather than almost circular, as well as the common statements which misleadingly describing Earth s orbit as elliptical rather than circular (Linstead et al., as cited in Todd & Hotan, 2008, p. 26). Although it is correct to describe Earth s orbit as elliptical it may be better, in a formal education context, to describe Earth s orbit as circular or approximately circular given the prevalence of the changing distance misconception. Method A general survey of students astronomical knowledge was undertaken involving high school students from year 8 to year 11 using a diagnostic test comprising 21 questions (O Byrne, 2001). These results were compared with results from the same diagnostic test administered in February 2008 to students taking Astronomy 101 at Curtin University of Technology. The sample was composed of 48 year 8 students, 52 year 9 students, 40 year 10 students and 36 year 11 physics students. The university undergraduate Astronomy 101 comparison group was comprised of 51 students who were enrolled in diverse courses including the physical sciences, engineering and education. 82% of the university students had studied TEE Physics. The results of selected questions within the diagnostic test which assess student understanding of phases of the moon, the seasons, and the relative motions of the Earth, Moon and stars were then examined. A small group of year 6 students were also tested on those concepts before receiving specific instruction to establish an approximate baseline for Western Australia students. Results The overall results showed an upwards trend in the number of correct answers with year level (Figure 1) however there was no differentiation in the results between change in knowledge through education and change in analytical ability through cognitive development Mean score ( /21 ) Uni Year group Figure 1 - Mean test result by year group

5 The Earth, Sun and Moon During classroom discussion the year 6 students expressed the knowledge that the Moon revolves around the Earth, the Earth revolves around the Sun, the rotation of the Earth causes day and night, and that the Earth is tilted [on its axis]. The high school students were not specifically interrogated on this knowledge as it was assumed the greater majority, if not all students, would hold this view. - Tilt of Earth s axis Examination of students awareness of the path of the Sun across the sky showed that 30% of students (year 8 33%, year 9 19%, year 10 25%, year 11 47%) could correlate the knowledge that the tilt of Earth s axis and their geographic location in the southern hemisphere results in the Sun not passing directly overhead at their location. The most popular alternative conception was that the Sun passes directly overhead every day at noon, given by 52% of students (year 8 44%, year 9 67%, year 10 58%, year 11 33%). - Rotation of Earth Although students could explain that Earth rotates to cause day and night the underlying belief that the Sun moves across the sky as a result of observation of the apparent movement of the Sun was revealed when background stars were illustrated and students were asked to identify the expected position of the Sun against the stars at sunset compared to noon. 11% of students (year 8 6%, year 9 12%, year 10 10%, year 11 17%) identified that the position of the Sun relative to the background stars would not significantly change over the course of a day. The most popular alternative conception was that the Sun would move westward, given by 54% of students (year 8 54%, year 9 50%, year 10 60%, year 11 53%), while 35% of students (year 8 40%, year 9 39%, year 10 28%, year 11 31%) considered that the Sun would move towards east. - The Moon s orbit While students could explain that the Moon revolves about the Earth, not all students could define the period of revolution. While some students were able to explain that the Moon orbits Earth with a period of approximately one month other students were uncertain of the period. When asked to describe the phase of the Moon six hours after a full moon had risen in the east 28% of students (year 8 35%, year 9 17%, year 10 25%, year 11 36%) were able to identify that the Moon s phase would still be a full moon. 59% of students (year 8 58%, year 9 73%, year 10 53%, year 11 47%) expressed the conception that the phase would have changed to a gibbous or quarter moon which was consistent with a hybridised view where the Moon orbits the Earth on a daily basis based on experience of the apparent movement of the Moon across the sky. 10% of students (year 8 6%, year 9 8%, year 10 13%, year 11 14%) considered that the Moon would become a crescent moon. The rationale described for this by one student was that as the Sun moved behind the Earth then Earth s shadow would fall across the Moon (geocentric orbits with eclipse explanation for lunar phases).

6 Phases of the Moon Given a diagram showing the Moon in a number of positions about Earth, students were asked to identify in which position the Moon would appear to be a crescent moon. 18% of students (year 8 21%, year 9 14%, year 10 18%, year 11 19%) could correctly identify the relative positions of the Earth, Moon and Sun that would result in a crescent moon being visible to observers on Earth. The most popular alternative choice selected by 38% of students (year 8 27%, year 9 40%, year 10 33%, year 11 53%) supported the eclipse explanation where the crescent moon is a result of Earth s shadow covering part of the Moon. Another question which asked which phase the Moon must be during a solar eclipse, where the Moon appears to cover the Sun, was correctly identified as a New Moon phase by 9% of students (year 8 10%, year 9 12%, year 10 10%, year 11 0%). The most popular alternative choice, nominated by 72% of students (year 8 65%, year 9 81%, year 10 65%, year 11 75%) was a Full Moon. 16% of students (year 17%, year 9 6%, year 10 23%, year 11 22%) suggested that no particular phase of the Moon was required for a solar eclipse. Seasons When asked what effect changing Earth s orbit to be a perfect circle about the Sun would have on the seasons, 10% of students (year 8 6%, year 9 14%, year 10 5%, year 11 17%) responded that the seasons would be unchanged. The most popular alternative answer given by 40% of students (year 8 27%, year 9 40%, year 10 53%, year 11 42%) was that we would no longer experience a difference between the seasons. Discussion Conclusions Acknowledgements Thank you to the students and teachers who participated in the surveys and assisted with the collection of data. References Anderton, J. (Ed.). (1990). Fundamentals of Science. Book 3. Melbourne: Longman Cheshire Pty Ltd.

7 Atwood, R., & Atwood, V. (1996). Preservice Elementary Teachers Conceptions of the Causes of Seasons. Journal of Research in Science Teaching, 33(5), Baxter, J. (1989). Children s understanding of familiar astronomical events. International Journal of Science Education, 11(5), Dunlop, J. (2000). How Children Observe the Universe. Publications of the Astronomical Society of Australia, 17, Jones, B., Lynch, P., & Reesink, C. (1987). Children s conceptions of the earth, sun and moon. International Journal of Science Education, 9(1), O Byrne, J. (2001). Astronomy Diagnostic Test Southern Hemisphere Edition version Retrieved September 14, 2008, from Parker, J., & Heywood, D. (1998). The earth and beyond: developing primary teachers understanding of basic astronomical events. International Journal of Science Education, 20(5), Sharp, J. (1996). Children s astronomical beliefs: a preliminary study of Year 6 children in south-west England. International Journal of Science Education, 18(6), Stahly, L., Krockover, G., & Shepardson, D. (1999). Third Grade Student s Ideas about the Lunar Phases. Journal of Research in Science Teaching, 36(2), Taylor, I. (1996). Illuminating Lunar Phases. The Science Teacher, 63(8), Todd, M., & Hotan, A. (2008). Misconceptions in Astronomy in WA students. SCIOS: Journal of the Science Teachers Association of Western Australia, 44(3), Trundle, K., Atwood, R., & Christopher, J. (2002). Preservice Elementary Teachers Conceptions of Moon Phases before and after Instruction. Journal of Research in Science Teaching, 39(7),