# Knowing and explaining in the context of Earth and space

James de Winter (University of Uppsala and University of Cambridge) and Richard Brock (King’s College London) highlight accessible and usable resources based on research into physics education

From 24 hours to 365 days and from MVEMJSUN* to OBAFGKM**, learning about the features of the universe may not seem to hold the same conceptual challenges that, for example, Newton’s Laws demand and can slip into recall-only territory.

However, supporting students to develop a meaningful understanding of the complex, multi-bodied, three-dimensional motions of astronomical objects beyond rote memorisation, presents many challenges. Justification of ideas can be problematic – can you convincingly provide evidence, from your own experience, that the Earth does go round the Sun?

Steinberg, Cormier and Fernandez carried out research to explore how American high school students (14-16-year-olds) were able to justify their answers to the question: Which of the following do you think best approximates the relative motion of the Earth and the Sun?

A. The Sun goes around the Earth.

B. The Earth goes around the Sun.

C. Neither A nor B are correct.

D. I do not know.

As best as you can, provide a proper and complete scientific argument for your answer.

Most students selected the correct answer (B=93%) and the researchers focused on students’ ability to provide a ‘complete scientific argument’. Responses were assessed on a scale from:

(1) Students use jargon, authority, circular reasoning or irrelevant observations or experiments.

to:

(5) Student cites observations or experiments distinguishing between two models and supports choice with proper explanation relevant to their answer.

The quality of explanatory responses was initially consistently low and the researchers implemented a teaching intervention to support students’ scientific argumentation with the following aspects:

• Teachers emphasise the process of science, rather than the presentation of facts.
• Students are asked to build models of the Earth and Sun’s motion with balls/nails/torches and then to justify observations.
• Students are not given the answers but are guided to develop explanations for their observations.
• Students are constantly asked to justify, explain, reason and interpret.

After the intervention, there was a significant increase in the quality of students’ correct scientific justification for their answers. In addition, the students scored well on a task asking them to explain a context not covered in the course (black holes).

As with all studies, caution is needed in suggesting that this is the correct/best/only way to teach. However, the paper contains useful aspects including:

• a rubric to assess the quality of student explanations
• suggesting a correct answer, by itself, does not indicate full understanding and so teaching and assessment should focus on students’ explanatory abilities
• a teaching approach to support students’ explanations.

* Order of the planets from the Sun

** Classification of the stars by their spectra and temperature