Changing Universe Models

Overview

Students investigate how explanations of the universe have changed as observations, evidence and technology improved. They compare geocentric and heliocentric models, consider Māori knowledge of the night sky and navigation, and build a timeline showing how scientific models develop rather than simply become “right” or “wrong”.

Learning intentions

• WALT describe and model relationships, scale and movement within the universe.
• WALT explain how evidence and technology can change scientific models.
• WALT compare different explanations of Earth’s place in the universe.
• WALT use evidence to justify why a model is useful or limited.

Success criteria

• I can place key ideas and discoveries in a logical timeline.
• I can describe the difference between geocentric and heliocentric models.
• I can link an observation or technology to a change in explanation.
• I can explain that models are useful representations, not exact copies of reality.

Curriculum links

• Earth and Space — describing and modelling relationships, structures, relative scale and behaviours in celestial systems.
• Earth and Space — classifying celestial objects using characteristics including orbit, size, shape and composition.
• Earth in Space — recognising that scientific understanding of the universe develops through models, evidence and improved astronomical measurement.
• Science capabilities and competencies: interpreting evidence, communicating explanations, thinking critically, and participating collaboratively.

Prior knowledge

Students should know that Earth is a planet, the Sun is a star, the Moon orbits Earth, and planets orbit the Sun. Elicit these ideas rather than assuming all students hold them securely.

Key vocabulary

Universe, model, evidence, observation, geocentric, heliocentric, orbit, gravity, telescope, galaxy, expanding universe, technology, scale, maramataka.

Lesson structure (60 minutes)

1. 0–7 min · Hook and wonder. Open with the opening mystery image and question: “If the Sun appears to travel across the sky, why do we say Earth moves?” Students make an individual claim, then discuss it with a partner. Invite several explanations without correcting them yet. Explain that people have used careful observations and models to answer this question. Briefly acknowledge that Māori communities developed detailed knowledge of stars, seasons, tides and navigation through long-term observation; maramataka is a living knowledge system, not merely a star calendar.

2. 7–15 min · Build shared understanding. Use the model comparison and vocabulary slides to show simple diagrams of the geocentric model, with Earth central, and the heliocentric model, with the Sun central to the Solar System. Clarify that “central” refers to the model’s arrangement, not necessarily the centre of the whole universe. Demonstrate orbiting with students or a ball-and-string model if available. Students add definitions and one labelled sketch to the universe models timeline worksheet. Stress that models simplify scale: classroom diagrams are not to scale.

3. 15–32 min · Evidence timeline investigation. Arrange students in five mixed-ability groups. Give each group one timeline station or event card from the evidence timeline instructions and display the class timeline headings: explanation, evidence, technology, limitation. Groups investigate one stage:

• ancient and medieval geocentric explanations;
• Copernicus and the heliocentric model;
• Galileo’s telescope observations, including Jupiter’s moons and the phases of Venus;
• Newton’s laws and gravity explaining motion and orbits;
• modern evidence for an expanding universe, including galaxy redshifts and observations from powerful telescopes. Students record: What did people think? What was observed? What changed or became better explained? They must distinguish evidence from an opinion or model. Teacher circulates and asks, “What did this observation make harder to explain?” and “What could the technology detect?”

4. 32–43 min · Jigsaw teach-back. Re-form groups so each new group includes a representative from each stage. Students teach their event in chronological order, using their worksheet notes. Each listener records one change in explanation and one piece of evidence. Groups then place their events on a shared floor or board timeline. Check chronology and correct the common error that Galileo invented heliocentrism; he gathered important telescope evidence supporting it.

5. 43–51 min · Differentiated modelling task. Groups choose a suitable challenge. Support groups match prepared teacher-provided labels and images to the two models and complete sentence frames: “The geocentric model placed…”, “Evidence from… supported…”. Core groups draw both models and annotate how one observation challenged the earlier model. Extension groups create a three-part explanation showing how improved instruments changed what could be observed, including why redshift supports an expanding universe. All groups answer: “Why might a model be replaced, refined or retained?”

6. 51–56 min · Misconception check and discussion. Use the agree-or-disagree discussion slides. Students hold up agree/disagree cards or show thumbs to respond: “The Sun moves around Earth because it rises and sets”; “A model is a guess with no evidence”; “Newton proved every idea about space”; “The universe is expanding into empty space.” Discuss that apparent motion depends on viewpoint, models are evidence-based representations, Newton improved explanations of motion and gravity but did not answer every question, and expansion describes increasing distances between galaxies on large scales rather than a simple explosion into pre-existing space.

7. 56–60 min · Exit ticket. Students complete the final section of the individual exit ticket questions without help: (1) contrast geocentric and heliocentric models; (2) name one observation or technology that changed an explanation; (3) explain why scientific models can change; (4) describe one idea they are still wondering about. Collect before students leave.

Resources

• the changing universe slide deck
• the universe models timeline worksheet
• Teacher-prepared event cards or short information strips
• Large paper or board space for the class timeline
• Sticky notes and coloured pens
• Balls, string or simple orbit demonstration materials
• Agree/disagree cards
• Images of Māori star knowledge, navigation or maramataka, selected respectfully and with context

Assessment

• Listen for students distinguishing an observation, evidence, model and explanation during group work.
• Check worksheet timelines, labelled models and teach-back explanations for accurate sequence and causal links.
• Use the exit ticket to identify whether students can explain why models change, not just recall names and dates.

Differentiation

• Provide a word bank, illustrated vocabulary, partially completed timeline and sentence starters for students needing support, including EAL learners.
• Read event information aloud, use high-contrast diagrams and allow oral recording or speech-to-text where appropriate.
• Pair students strategically and assign roles such as reader, evidence finder, illustrator and reporter.
• Extend confident students by asking them to explain the difference between evidence supporting a model and evidence proving it permanently, or to compare the limits of a classroom model with the real scale of the universe.

Misconceptions to monitor

• Day and night are caused by the Sun travelling around Earth.
• The heliocentric model places the Sun at the centre of the entire universe; it describes our Solar System.
• Galileo worked alone or “proved” heliocentrism through one observation.
• Gravity is only a force on Earth.
• The Big Bang was an explosion from one central point into already existing space.
• A scientific model is a random guess rather than a testable representation based on evidence.