Australian Curriculum v9 / ACiQ Year 7 Science - Unit 9 - Earth-Sun-Moon cycles and seasons

Earth-Sun-Moon cycles and seasons

Model rotation, revolution and changing relative positions to explain day, year, Moon phases and seasons.

Updated 2026-07-24 - 8 min read

Model rotation, revolution and changing relative positions to explain day, year, Moon phases and seasons. This note connects the core scientific model to a worked example, an inquiry design and the limits of the evidence.

Core model

Relative position and illumination produce predictable cycles. Rotation explains day and night; revolution sets the yearly cycle; the Moon's orbit changes phases; Earth's persistent axial tilt changes Sun angle and day length.

Accessible diagram description: Sun at centre-left sends parallel light arrows. Four Earth positions around the orbit all show the axis tilted the same direction. The Southern Hemisphere points more toward the Sun at the December position and away at the June position.

A model is useful because it highlights relationships that help explain or predict evidence. It is not a perfect copy of reality. Always state what the representation includes, what its arrows or symbols mean, and one relevant limitation.

Authored representation workshop

Earth's tilt through four orbital positions

Accessibility description: The Sun is central. Earth appears at March, June, September and December positions with its axis parallel at every position. The Southern Hemisphere tilts most away from the Sun in June and most toward the Sun in December.

Represented parts

  • Sun
  • March position: axis keeps the same direction
  • June position: Southern Hemisphere tilted away
  • September position: axis keeps the same direction
  • December position: Southern Hemisphere tilted toward

Represented relationships

  • March position: axis keeps the same direction -> June position: Southern Hemisphere tilted away (Earth revolves)
  • June position: Southern Hemisphere tilted away -> September position: axis keeps the same direction (Earth revolves)
  • September position: axis keeps the same direction -> December position: Southern Hemisphere tilted toward (Earth revolves)
  • December position: Southern Hemisphere tilted toward -> March position: axis keeps the same direction (Earth revolves)
  • Sun -> June position: Southern Hemisphere tilted away (parallel sunlight)
  • Sun -> December position: Southern Hemisphere tilted toward (parallel sunlight)

Learner action: Compare the June and December positions while keeping the axis direction fixed. Explain the opposite daylight pattern in the two hemispheres and identify one scale feature the diagram deliberately simplifies.

Approximate monthly daylight in Brisbane

Accessibility description: Daylight is shortest near June and longest near December, forming a smooth yearly cycle rather than changing with a sudden seasonal switch.

| Month | Approximate daylight (hours) | | --- | --- | | January | 13.6 | | March | 12.2 | | June | 10.5 | | September | 12.0 | | December | 13.8 |

*Rounded published sunrise-sunset durations for one location; values are for model interpretation, not navigation.*

Learner action: Use only the supplied or teacher-approved published daylight data. Plot the yearly pattern, identify the shortest and longest daylight periods, connect them to the fixed-axis orbit model, and state why daylight alone cannot explain every daily temperature change. No direct Sun observation is permitted.

The representation and table are supplied evidence. Do not replace a represented value, relationship or anomaly with an expected result. If a visual version is created, preserve this text-equivalent information and define every symbol, arrow, heading and unit.

Worked example

The reasoning routine is:

  1. identify the observation, measurement or represented relationship
  2. select the relevant science idea
  3. connect the idea to the evidence in a complete sentence
  4. qualify the answer when the evidence or model has a boundary

Inquiry connection

Question: How do monthly daylight hours in Brisbane change across the year?

Reasoned hypothesis: If months move from June toward December, daylight hours will generally increase because the Southern Hemisphere tilts progressively toward the Sun.

  • Independent variable: month of the year
  • Dependent variable: daylight duration
  • Relevant controls: location and the method used to calculate sunrise and sunset
  • Hazard: direct observation of the Sun can damage eyes
  • Risk control: use published data or indirect shadow methods and never look directly at the Sun
  • Reproducibility detail: cite the data source, location, dates, time zone and daylight calculation

Possible data finding: daylight rises from about 10.5 hours near June to about 13.8 hours near December in a smooth cycle.

Evidence-based interpretation: The pattern supports the tilt model for Brisbane.

Limitation: Daylight duration alone does not include cloud, ocean currents or all factors affecting daily temperature.

This investigation frame recurs across Year 7 Science. A sound response names a testable relationship, matches the hypothesis to the same variables, manages a realistic risk, specifies quantities and measurement rules, analyses the full data pattern, supports a claim with evidence and states what the evidence cannot establish.

Common errors and corrections

  • Error: Explaining seasons mainly by distance. Correction: Return to the core model and identify the exact evidence or relationship before answering.
  • Error: Saying the Moon makes its own visible light. Correction: Return to the core model and identify the exact evidence or relationship before answering.
  • Error: Saying Moon phases are normally Earth's shadow. Correction: Return to the core model and identify the exact evidence or relationship before answering.
  • Error: Drawing Earth's axis changing direction at every orbital position. Correction: Return to the core model and identify the exact evidence or relationship before answering.

Practice

  1. Distinguish rotation from revolution.
  2. Explain a Moon phase with light direction.
  3. Use daylight data to identify Southern Hemisphere summer.
  4. State one scale limitation of an orbit model.

Transfer task

Apply the topic to the investigation below without relying on a teacher or AI to mark the reasoning.

Evidence status: activity only. Use the task-specific rubric below for self-review or teacher feedback; completion does not automatically award mastery.

Context: How do monthly daylight hours in Brisbane change across the year?

  1. Rewrite the question if it does not clearly name the relationship and measurable outcome.
  2. Write the matching reasoned hypothesis: include the expected direction and the science idea that justifies it.
  3. Identify the independent variable, dependent variable and at least three relevant controlled variables.
  4. Write a six-step reproducible method. Include equipment, quantities, units, an ordered measurement rule and at least three repeated trials for each condition.
  5. State the hazard, possible harm and a practical control. The control must address the stated hazard rather than being generic advice.
  6. Design a results table with headings and units. State which graph or other representation would best show the relationship and why.
  7. Use this possible finding: daylight rises from about 10.5 hours near June to about 13.8 hours near December in a smooth cycle. Describe the overall pattern, identify any anomaly and state a reasonable check.
  8. Write a conclusion using claim, specific evidence and scientific reasoning. Finish with this limitation: Daylight duration alone does not include cloud, ocean currents or all factors affecting daily temperature.

Correction guide: Compare the question and hypothesis to confirm they use the same two variables. In the method, circle every quantity and unit and underline every controlled condition. In the data response, separate the broad pattern from any anomalous result. In the conclusion, highlight the evidence sentence and box the limitation. If one of these parts is absent, revise that part before checking the scientific vocabulary.

An excellent transfer response is precise without pretending the evidence is perfect. It makes the chain from question to method to data to claim visible, and it explains how the core model applies in the unfamiliar context.

Task-specific inquiry rubric

  • Question and hypothesis for month of the year and daylight duration: Names the same measurable relationship in both and gives a scientific reason. Revise if needed: Align the changed factor, measured outcome and predicted direction.
  • Fair, safe and reproducible method: Controls location and the method used to calculate sunrise and sunset, manages "direct observation of the Sun can damage eyes", and specifies quantities, units, measurement rules and repeats. Revise if needed: Replace vague directions and generic safety advice with operational detail.
  • Data and analysis plan: Provides labelled headings and units, an appropriate representation, a way to describe the whole pattern and a rule for checking anomalies. Revise if needed: Show how evidence will answer the question before collecting it.
  • Scientific interpretation and boundary: Links the expected evidence to earth-sun-moon cycles and seasons and anticipates this boundary: Daylight duration alone does not include cloud, ocean currents or all factors affecting daily temperature. Revise if needed: Explain the science link and state what the design cannot establish.

Self-check

For each response, check:

  • Did I use the correct scientific vocabulary?
  • Did I refer to the specific evidence, feature or data?
  • Did I explain the link rather than only naming it?
  • Did I avoid claiming more than the model or data support?
  • If an investigation is involved, did I address question, hypothesis, variables, safety, reproducibility, data, evidence and limitations?

Sources