When planning for teaching in your classroom, it can be useful to see where a sequence fits into the larger picture of science. This unit is anchored to the Science Understanding Core concepts for Earth and space sciences.

• Earth is part of an astronomical system; interactions between Earth and celestial bodies influence the Earth system.

In Year 6, this involves describing the movement of Earth and other planets relative to the Sun and model how Earth’s tilt, rotation on its axis, and revolution around the Sun relate to cyclic observable phenomena, including variable day and night length.

This core concept is linked to the key science ideas:

• Patterns can be used to identify cause and effect relationships (including day and night and Moon phases) and make predictions. (Patterns, order and organisation)
• Some patterns have an underlying cause that cannot be observed at the same spatial or temporal scale. (Patterns, order and organisation)
• Generalisations about the relationship between the Earth, Sun and Moon can be made. (Systems)
• Models can be used to investigate relationships between celestial objects in the solar system. (Systems)
• Scale models of the solar system can be used to represent relationships between the length of day in different parts of the world. (Scale and measurement)
• The use of appropriate units of measurement is important to understand and compare the scale of distances between celestial objects. (Scale and measurement)

When your students next progress through this core concept, they will model cyclic changes in the relative positions of the Earth, Sun and Moon and explain how these cycles cause eclipses and influence predictable phenomena on Earth including seasons and tides (Year 7).

Eratosthenes (Era–tos–the–neez) was a Greek mathematician and astronomer who lived around 200BC. At this time many people believed that the Earth was flat, based on their everyday experiences. Eratosthenes used scientific methods to disprove the non-scientific ‘flat Earth’ idea.

During the Northern Hemisphere’s summer solstice in the 2nd century BC, Eratosthenes undertook an investigation into the size of the Earth. During the summer solstice the North Pole is tipped closest to the Sun, which means it will rise the highest in the sky on this day. However, it is only possible for the Sun to be exactly overhead for cities that are on the Tropic of Cancer. The ancient Egyptian city of Swenet (Syene to the Ancient Greeks and Aswan today) is on the Tropic of Cancer. The city of Alexandria is north of Swenet.

By noting the lack of shadows at high noon in Swenet, and measuring the shadows visible at high noon in Alexandria, Eratosthenes could calculate the angle of elevation of the Sun. It was one-fiftieth of a circle, therefore he estimated that the distance between the two cities was one-fiftieth of the circumference of the Earth.

He checked the distance between the two cities by calculating travel times between them, and came up with a solution that was fairly accurate—in fact, with an error of less than 2 per cent compared to the values calculated using modern and more accurate measuring tools! This is surprising, given the possible sources of error, including using a model that assumed the Sun appeared as a point of light in the sky, not a disc, and distances calculated by overland travel were not the most reliable, as deviations were sometimes made to ensure water supply.

The dialogue presented in the But it looks flat! Resource sheet is imagined. Many other philosophers in previous centuries, including Pythagoras (who noted the shapes of lunar eclipses) and Aristotle, had argued that the Earth was spherical. Eratosthenes was chosen as a subject for the text as he actually conducted the scientific investigation described, not only to show that the Earth was spherical but to also calculate its size.

Scientific knowledge is a set of explanations made by scientists based on observations and evidence. These explanations have been built up over time to explain how the world works. They continue to be revised as new evidence emerges.

Scientists conduct investigations to test ideas and find evidence; however, the conclusions and explanations they draw from the evidence can be influenced by the life experiences and beliefs of the scientists. Scientists are a part of the world they study, and their ideas can be influenced by it.

When scientists disagree, they first check the available information. In scientific publications the authors highlight their procedures so that the investigations can be replicated. Scientific debate is, however, generally about what conclusions can be drawn from the available evidence.

This lesson illustrates many of these aspects. Students see an example of people using their everyday experiences to form their scientific views in the But it looks flat! Resource sheet. They are later invited to do similar when they select which claim about the position of the Earth, Sun and Moon they believe is correct.

The But it looks flat! Resource sheet also represents how Eratosthenes had a theory, devised an investigation to test his ideas, used the data collected as proof of these ideas, and then used that as a springboard for further investigation. It provides a good, albeit simplified, example for students of how scientists think and work. 

You might take the discussion further with students by asking questions about how the same investigation might be carried out today, how it would be communicated/shared with the community, and how its validity and reliability might be assessed.

There are many ways you might record which claim students agree with. The manner you choose will depend on your class and context.

Firstly, determine if it is more appropriate for students’ responses to remain confidential or if it is okay for them to share their thoughts publicly.

If you decide to keep responses confidential you might talk to students individually and record their thinking using anecdotal records, or you might have students record their selection and reasoning in their science journals.

If you think your students are comfortable enough to share the data publicly, then you might place posters of each claim around the room and ask students to record their name and reasoning on the appropriate poster, or you might use the cumulative listing technique along with discussion to gather the data.

Finding out how confident students are in their choice of claim and the reasoning behind their choice is also very valuable information.

Students who have not had reason or opportunity to think about these concepts before may select a claim at random, or because their friends did. This does not necessarily mean they are holding alternative conceptions, or have no conceptions at all, but simply that they have not had opportunity to articulate their thinking about it before. Over the course of the sequence, these students may make representations that actually demonstrate that, when given the opportunity and time to think methodically, they articulate currently scientifically accepted ideas.

Conversely, some students may confidently state that Claim 3 (the Moon circles the Earth while the Earth circles the Sun) is correct, but when questioned further may have no reasoning beyond I was told, I read it in a book, or I just know. Over the course of the sequence these students should be encouraged to relate their experiences in investigations to the claim they selected, so that they might cite experiences and evidence to support their beliefs.

Recording each student’s selection, their reasoning for it, and how confident they feel in that choice, allows both you and them to reflect on their choice at the end of the sequence to see if and how their thinking has changed.

One of the key aspects of a TWLH chart is its ability to guide a student in metacognitive (the ability to think about your thinking) processes. By focusing on what we think we know, students are encouraged to see learning as a journey where new scientific evidence and experiences may change their thinking. This is a very important aspect of thinking scientifically.

In this instance, students are considering their initial knowledge of the relative position of the Earth, Sun and Moon and their movements. In this phase of learning students should be encouraged to populate the T and W sections of the chart.

Using sticky notes or individual slips of paper to record ideas allows them to be easily moved and re-categorised as required.

Students might contribute ideas openly during a class discussion. Placing students’ initials on the sticky notes as their ideas are recorded supports them (and you as the teacher) to track the development of their understanding over the course of the sequence.

Having students give anonymous contributions can also be beneficial. It can encourage a broader range of ideas, as well as allowing reluctant students the opportunity to contribute without fear. Students can record their ideas privately on sticky notes. These can then be collected and re-distributed at random. 

Teachers are best placed to make decisions about the most appropriate method of collecting students’ ideas.

The Question Formulation Technique (Santana & Rothstein, 2018) outlines four steps for students to generate, refine, and select useful questions. These are:

1. Examine stimulus.
2. Brainstorm questions.
3. Improve questions: change closed questions or statements into open questions.
4. Prioritise questions according to importance, ability to be investigated, what will help with the Act phase, and how it will be answered.

Students should work together in small groups of 3-5.