Year 7 Science · Unit 4 · Lesson 7
Master Worksheet
Learning Goals
1. Name the scientist who worked out that the planets move in elliptical orbits, and describe the shape of an elliptical orbit.
Find the error
Mia’s summary
Line 1: The Earth-centred picture puts a still Earth in the middle of everything.
Line 2: In 1543 Copernicus used a telescope to prove that the Sun is at the centre.
Line 3: Looking through a telescope showed that every object in the sky circles the Earth.
Line 4: In the end the geocentric model was replaced because the Sun-centred idea became more popular.
2. Three of Mia’s four lines contain an error. Name each wrong line and rewrite it correctly.
Which model explains it better?
For each observation write geocentric, heliocentric or both equally, then give a reason. One mark for each row with a correct choice and reason.
| Observation | Better model | Reason |
|---|---|---|
| The Sun rises, crosses the sky and sets each day. | ||
| Four small moons travel around Jupiter. | ||
| The planets seem to make strange loops in the sky. | ||
| Venus shows a full set of phases, from crescent to nearly full. |
Scenario: a debate in 1600
Two astronomers argue
Astronomer G supports the Earth-centred model. Astronomer H supports the Sun-centred model of Copernicus. Both of them point to the Sun crossing the sky each day as proof that they are right. Nobody yet has a telescope.
3. Explain why the Sun crossing the sky cannot settle their argument, and why many people in 1600 still preferred Astronomer G’s model.
Read the data: a timeline of the model
Timeline
| When | Who | What happened |
|---|---|---|
| About 150 CE | Ptolemy | Writes down a detailed Earth-centred model |
| 1543 | Copernicus | Publishes the Sun-centred model, as an idea on paper |
| Early 1600s | Kepler | Uses years of careful measurements to show orbits are elliptical |
| About 1610 | Galileo | Sees Jupiter’s moons and the phases of Venus through a telescope |
| Later | Scientists | Reject the geocentric model; the heliocentric model is accepted |
Source: dates from the lesson.
4. Use Table 1 to explain why the model did not change in 1543 but did change after the early 1600s. Name the kind of change that happened.
5. Evaluate this statement: “A scientific model that changes must have been bad science in the first place.” Justify your answer using the ideas of Ptolemy and Copernicus and the evidence that settled between them.
Question 1
Johannes Kepler (1). A slightly stretched oval, not a perfect circle (1). [2 marks]
Find the error
2. Line 2: Copernicus published the Sun-centred idea on paper; the telescope evidence came from Galileo around 1610 (1). Line 3: the telescope showed that not everything circles the Earth: Jupiter has moons of its own (1). Line 4: it was replaced because new evidence no longer fitted it, not popularity (1). Line 1 is correct. [3 marks]
Which model explains it better?
Sun crossing the sky: both equally; the Sun moving around the Earth or a spinning Earth both explain it (1). Jupiter’s moons: heliocentric; they orbit Jupiter, not the Earth (1). Loops: heliocentric; a Sun-centred model explains the planets’ movements far more simply (1). Venus: heliocentric; the geocentric model could not produce a full set of phases (1). [4 marks]
Scenario: a debate in 1600
3. Both models explain the Sun crossing the sky, so it cannot tell them apart (1). With eyes alone there was no clear new evidence to decide (1). People preferred the old model out of habit, and because we do not feel the Earth moving (1). [3 marks]
Read the data: a timeline of the model
4. In 1543 the Sun-centred model was only an idea, with no new evidence (1). In the early 1600s Kepler’s measurements and Galileo’s telescope gave evidence the old model could not explain (1). The geocentric model was modified and then rejected (1). [3 marks]
Question 5
Marking guide: 1 position (disagree); 1 a model is a simplified picture, our best current explanation; 1 the geocentric model fitted what people could see with their eyes, so it was good science with the tools of the time; 1 names new evidence (Jupiter’s moons, Venus’s phases, elliptical orbits); 1 the model was modified, then rejected and replaced; 1 changing with evidence means understanding keeps improving, which is a strength. [6 marks]
Model answer: I disagree. A model is our best current picture. The geocentric model fitted what people saw with their eyes, so it was good science for its time. When the telescope showed Jupiter’s moons and Venus’s phases, and Kepler found elliptical orbits, it was modified, then rejected. Changing with evidence is how science improves.
Common error: treating Copernicus’s 1543 idea as the moment the model changed.