Semantic Analysis

This level of analysis focused on interpretation of marks and their configurations. This analysis consisted of three principles.

Principle 4: Harmony

Diagrams should be designed so that there is consistency in the meaning associated with each mark.

Design of several diagrams violates this principle.

Inconsistent use of colour: Artists of nine diagrams used colour in a way that might confuse viewers. Artists of Diagrams 14b and 20 used white colour to represent half of the Moon illuminated by the Sun‘s rays, and used dark colours to represent half of the Moon not lit by the Sun‘s rays. However these artists used only the white colour on the surface of the Earth, giving a false impression that the entire surface of the Earth is always illuminated by the Sun‘s rays. In Diagram 22b, white colour represents half of the Moon illuminated by the Sun‘s rays while a dark- grey colour represents half of the Moon not lit by the Sun‘s rays. However, only the dark-grey colour has been used on the surface of the Earth, giving false impression that the Sun never shines on Earth. Readymade visual aids like charts can be used to show learners that on paper, both halves of the Earth and the Moon are illuminated by the Sun at all times. In the absence of these aids, teachers would have to make diagrams showing that the Sun illuminates halves of the Moon and the Earth at all times.

In Diagrams 16 and 21a, yellow colour represents half of the Moon illuminated by Sun‘s rays while brown and blue colours represent half of the Earth illuminated by the Sun‘s rays (the latter colours probably indicate parts of the Earth covered by land and water respectively). In Diagram 11, white colour represents half of the Moon illuminated by the Sun‘s rays while light-grey colour represents half of the Earth illuminated by the Sun‘s rays. These inconsistencies give a false impression that sunlight shining on the surface of the Earth is different from sunlight shining on the surface of the Moon. Impact of these inconsistently can be minimised by telling learners that the shaded colours should be the same, i.e. the same colour should represent halves of the Earth and the Moon illuminated by the Sun‘s rays and halves in darkness. Usage of readymade charts can help illustrate this point.

In Diagrams 8, 19 and 24, black and dark-grey colours represent unlit halves of the Earth and the Moon while a light-grey colour represents the area surrounding the Moon (i.e. the night sky). This gives a false impression that darkness of the night sky differs from darkness of the unlit half of the Moon. No inscriptions have been provided to explain what each colour represents. This problem can be solved fairly easily by telling learners that the dark colours have to be the same.

Inconsistent number of moon shapes in a diagram: The number of moon shapes in the Moon‘s

orbital path should be equal to the number of moon phases illustrated in the diagram to help viewers understand the reason for the shape of the Moon in each position. Two diagrams violate this principle. Diagram 17 illustrates the Moon in eight positions around the Earth, but illustrates only four phases of the Moon. Learners using this diagram might not know what the Moon looks like in the other four positions. Diagram 20, on the other hand, illustrates the Moon in four positions around the Earth, but illustrates eight phases of the Moon. No explanation has been given as to why the other four positions of the Moon are not illustrated. Learners using this diagram would have no opportunity of using the Earth-Moon-Sun system to determine the appearance of the Moon in the missing four positions. This problem can be addressed by using charts and modelling activities which should show the Moon‘s orbit as continuous while at the same time illustrating corresponding phases. In the absence of resources these resources, teachers might have to draw diagrams illustrating the Moon in eight positions around the Earth, and corresponding Moon phases. In Book 14, the first diagram (Diagram 14a) illustrates eight phases of the Moon while the second (Diagram 14b) illustrates the Moon in four positions around the Earth. However, authors made no effort to link information in the two diagrams. As a result, the two diagrams are independent of each other, and thus, do not violate this principle.

Inconsistent size of moon shapes in a diagram: In Diagrams 17 and 23, symbols representing

phases of the Moon are larger than symbols representing the Moon in its orbital path around the Earth. In Diagrams 19 and 20, on the contrary, symbols representing phases of the Moon are smaller than symbols representing the Moon in its orbital path around the Earth. These inconsistencies give a false impression that the Moon orbiting the Earth is not equal in size to the Moon visible from Earth. Readymade visual aids (e.g. charts) could be mostly suited to show learners that the shapes are actually equal in size. In the absence of these aids, the problem can

easily be addressed by telling learners that the shapes should be the equal in size (the information that might be found in the text).

Khanyane (2002) found a similar problem of inconsistent size on a diagram using three steps to illustrate formation and breakdown of ozone. Oxygen atoms in the second step were larger than oxygen atoms in the other two steps, despite the fact that the three components were meant to give a unified message. Thus, the problem identified in this study has been documented in at least one previous study.

Inconsistency in representation of Sun’s rays: In Diagram 18, a circular shape with radial lines represents the Sun and the Sun‘s rays. In addition, parallel arrows represent the Sun‘s rays illuminating the Earth and the Moon. The arrows overlap the radial lines representing Sun‘s rays. This erroneously implies that the Sun radiates both parallel and radial light rays. The book prescribes no other information dealing with phases of the Moon. Teachers who have access to other visual aids can use them to illustrate that the Sun radiates only one type of rays, and to further illustrate that the rays become parallel when they reach the Earth because of relative sizes and distance between the Earth and the Sun. In the absence of these aids, teachers might have to make appropriate drawings for the learners.

Principle 5: Non-ambiguity

Ambiguous use of marks should be avoided, as this might prevent viewers from understanding meanings of the marks.

Three types of violations have been noted.

Ambiguous use of black and white colours on phases of the Moon: In Diagrams 1, 5, 6, 7, 12, 13, 14, 19 and 24, bright colours (white or yellow) represent part of the Moon visible from Earth while dark colours (black or dark-grey) represent part of the Moon not visible from Earth. No inscriptions have been provided to explain what each colour represents. Some viewers might interpret the dark colours as representing part of the Moon visible from Earth because dark colours (on a white paper) attract the eye more than light colours.

This argument is supported by drawings made by two of 50 pre-service teachers who completed a moon chart in Bell and Trundle‘s (2008) study, and seven of 24 pre-service teachers who completed a moon chart in Wilhelm et al.‘s (2008) study. The two pre-service teachers who participated in Bell and Trundle‘s study shaded part of the Moon visible from Earth and left the invisible part as white. On the other hand, the seven pre-service teachers who participated in Wilhelm‘ et al.‘s study switched their method of shading, from shading visible part of the Moon to shading non-visible part of the Moon. These results indicate that some people consider the shaded part as representing visible part of the Moon; while on the other hand, diagram illustrators consider the white part as one being visible from Earth. Thus, without explanation of what each colour represents, different viewers might ascribe different meanings to dark and light colours in diagrams. This issue can easily be addressed by telling learners what each colour represents.

Ambiguous presence of lines inside moon shapes: Diagrams 20 and 21a have lines inside the moon shapes. There is no obvious meaning for these lines, and no explanations are provided to explain what the lines represent. For this reason, different viewers might ascribe different meanings to these lines. This problem would be difficult to correct because it is not clear what the lines represent.

Ambiguous presence of lines between the Earth and the Moon: Diagrams 15b, 22b and 24 have lines between the Earth and each of the eight positions of the Moon in its orbital path. In Diagram 15b, it appears as if the lines indicate half of the Moon visible from Earth, but no inscriptions have been provided to confirm this speculation. In Diagrams 22b and 24, there is no obvious meaning for these lines, and no inscriptions are provided to explain what the lines represent. As a result, different viewers might ascribe different meaning to these lines. This problem, too, would be difficult to correct because it is not clear what the lines represent.

Principle 6: Scientific accuracy

Diagrams should be designed so that marks accurately represent scientific concepts.

The design of several diagrams violates this principle.

Diagram 20 illustrates the Moon orbiting the Earth in a counter clockwise direction. This suggests that the Moon has been drawn as seen from the northern hemisphere. However, artists of the diagram drew phases of the Moon as they would be seen from the southern hemisphere. As a result, there is no correspondence between the Earth-Moon-Sun system and phases of the Moon (except for Full Moon and New Moon in which the Moon appears to be the same in both hemispheres). Modelling activities and charts can help to correct this information. Also, teachers‘ drawings can help to clarify problems made by the diagram.

The discussion under Principle 4 shows that for Diagram 18, the radial lines representing the Sun‘s rays overlap parallel arrows representing the Sun‘s rays shining on the Earth and the Moon. This implies that the Sun radiates both parallel and radial light rays. This is scientifically incorrect because the Sun emits radial rays only (fraction of these rays appears to be parallel because of relative sizes and distances between the Earth and the Sun). A further problem with Diagram 18 is that the Sun appears to illuminate more than half of the Earth and the Moon‘s surfaces. This is incorrect, and implies that the Sun illuminates more than half of the Earth and the Moon‘s surfaces at any particular point in time. Thus, the artists of this diagram have misrepresented the amount of the Earth and the Moon's surfaces illuminated by the Sun‘s rays. The fact that the diagrams is independent means that teachers using this book have to find other resources to help learners understand that the Sun emits radial rays only, and to further show that the rays illuminate half of the Earth and the Moon at any given point and time. Teachers who have no access to other resources might have to draw correct diagrams for the learners.

 Artists of six diagrams used wrong symbols to represent the New Moon phase. In three of these diagrams (2, 17 and 22a), artists used crescent shapes to represent New Moon while the in the other three diagrams (10, 13 and 23), artists used circular ring shapes to represent New Moon. These representations falsely imply that the Moon appears to be crescent-or ring-shaped during the New Moon phase (the Moon is not visible during this phase).

 Artists of Diagrams 6 and 7 mistakenly used gibbous shapes to represent the Waning Crescent moon phase.

 Artists of Diagram 13 used a waning crescent shape to represent both Waxing and Waning Crescent phases. In addition, the artists used a waning gibbous shape to represent both Waxing and Waning Gibbous phases.

 Artists of two diagrams used crescent shapes to represent quarter moons. Artists of Diagram 9 used a waning-crescent shape to represent Last Quarter, while artists of Diagram 11 used waxing and Waning Crescent shapes to represent First Quarter and Last Quarter respectively.

 Artists of two diagrams (18 and 20) each used the same shape to represent Waxing and Waning Gibbous phases. As a result, the Moon appears to be the same during Waxing and Waning Gibbous phases (which is not the case in real life).

Modelling activities can be a good way to show learners appropriate shapes of the Moon seen from Earth as the Moon orbits the Earth. Also, teachers can make drawings to show correct shapes to the learners. If teachers do not realise that the diagrams have incorrect information, then this information might be passed on to the learners.

None of the three studies which analyzed diagrams illustrating phases of the Moon in school textbook reported the problem of inaccurate shapes representing phases of the Moon (Dove, 2002; Engeström, 1991; Martinez-Pena & Gil-Quilez, 2001). However, Trundle et al. (2008) found this problem in diagrams illustrating moon shapes in children‘s story books. Trundle et al. (2008) found that one fifth of 772 illustrations were scientifically incorrect, and argued that these illustrations might enhance misconceptions.

Diagram 10 illustrates eight phases of the Moon in a linearly arranged manner. The diagram has arrows indicating waxing and waning phases of the Moon. The arrow indicating the waxing stage is positioned between New Moon and Waning Gibbous while the arrow indicating the waning stage is positioned between Waning Gibbous and Last Quarter. This incorrectly suggests that the Moon stops waxing only at the Waning Gibbous stage (it actually stops at Full Moon) and starts to wane from Waning Gibbous (not after Full Moon as should be the case). This inaccuracy can easily be corrected by telling learners that the Moon stops waxing at Full Moon, and starts waning immediately after the Full Moon phase. Textual information can also be used to correct this inaccuracy.

In Diagram 19, an outline of Africa can be seen on the earth shape, suggesting that the Earth has been drawn as seen from the side (not one of the poles). In this situation, the Moon's orbital path should be an oval. However, this orbital path has been drawn as circular in this diagram, violating

scientific accuracy of the illustration. A modelling activity can be used to show that Africa cannot be seen when the Moon‘s orbit is viewed from one of the poles.

Artists of five diagrams used incomplete terms to label phases of the Moon: artists of Diagrams 5 and 12 used the terms ‗waxing‘ and ‗waning‘ instead of Waxing Gibbous and Waning Gibbous. Artists of Diagrams 6 and 24 used the terms ‗new‘ and ‗full‘ instead of New Moon and Full Moon. Artists of Diagrams 5, 8, 12 and 24 used the term ‗crescent‘ instead of Waxing Crescent and Waning Crescent. Artists of Diagrams 8 and 24 used the term ‗gibbous‘ instead of Waxing Gibbous and Waning Gibbous. Learners using these diagrams might not know correct names of these moon phases. This problem can easily be corrected by telling learners appropriate names of Moon phases. Textual information can also help learners to know these names.

Artists of ten diagrams used inappropriate terms: Artists of Diagrams 5, 12 and 14a used the term ‗half Moon‘ instead of the terms First Quarter and Last Quarter. Artists of Diagram 24 used the term ‗half‘ to label each of these phases of the Moon. Artists of Diagrams 7, 9 and 10 used the terms ‗first crescent‘ and ‗last crescent‘ instead of Waxing Crescent and Waning Crescent respectively. Artists of Diagrams 13 and 15a used the term ‗gibbous moon‘ instead of the terms Waxing Gibbous and Waning Gibbous. In addition, Artists of Diagram 13 used the term ‗crescent moon‘ instead of the terms Waxing Crescent and Waning Crescent. Artists of Diagram 6 used the terms ‗old crescent‘ and ‗near full‘ instead of Waning Crescent and Waning Gibbous respectively. Artists of the same diagram used the term ‗partly waned‘ to label a gibbous moon, erroneously drawn to represent a Waning Crescent phase. Learners using these diagrams might not know correct names of these moon phases. It appears that artists wanted to give learners an idea about phases of the Moon (e.g. half, crescent, gibbous or full), but not necessarily the exact names of these phases.

N.B.: Some books present this content in books designed for learners in lower grades while others present the information in books designed for learners in senior grades. If students learn about moon phases in earlier grades and never again, then the learners in these grades need to know the names of all phases of the Moon.