Lesson 14

Teacher’s Description: This lesson develops learners’ understanding of how astronomical ideas are tested through careful planning, reliable observation and thoughtful evaluation of evidence. It follows Lesson 13 on developing hypotheses and prepares learners to apply those hypotheses in practical or classroom-based investigations. The central message is that scientific conclusions should not be based on a single observation: confidence grows when measurements are repeated, conditions are controlled, results are recorded accurately and findings are compared with a clear prediction. The lesson can be delivered in approximately 60–90 minutes, depending on the depth of discussion, the amount of modelling required and whether learners complete the planning activities independently or collaboratively. Begin with the Moon-and-star-count scenario in the starter. Ask learners whether two observations provide enough evidence to support the claim that more stars are visible when the Moon is fainter. Encourage them to identify alternative explanations, including cloud cover, light pollution, tiredness, changes in observing time or differences in the area of sky counted. Use responses to establish the difference between an interesting result and reliable evidence. Reinforce the golden rule that repeated, consistent observations are more persuasive than one isolated result. In Main 1, model how to turn a hypothesis into a fair test. Guide learners through the five planning questions: what they predict, what they will change, what they will measure, what they will keep the same and how they will check the result. Explicitly introduce the independent variable, dependent variable and control variables, linking each term to the astronomy example. Stress that changing more than one condition makes it difficult to identify the cause of any difference. Learners can discuss the worked example in pairs before adapting the structure to a question of their own. Check that their proposed measurements are numerical or otherwise clearly observable and that repeats are built into the method.