The Earth and the Moon

Objectives

Lesson outcomes

Explain the apparent daily motion of the Sun and the cycle of day and night using the Earth's rotation on a tilted axis.
Explain the seasons using the Earth's yearly orbit around the Sun and the tilt of its axis.
Explain the Moon's cycle of phases using the Moon's monthly orbit around the Earth.
Define average orbital speed as distance travelled divided by time taken and use it in simple space contexts.

Syllabus

CIE 0625 syllabus points

4 linked

6.1.1.1 Know that the Earth is a planet that rotates on its axis, which is tilted, once in approximately 24 hours, and use this to explain observations of the apparent daily motion of the Sun and the periodic cycle of day and night
6.1.1.2 Know that the Earth orbits the Sun once in approximately 365 days and use this to explain the periodic nature of the seasons
6.1.1.3 Know that it takes approximately one month for the Moon to orbit the Earth and use this to explain the periodic nature of the Moon’s cycle of phases
6.1.1.4 Define average orbital speed from the equation

Definitions

Required definitions

Average orbital speed
distance travelled in one complete orbit divided by the time taken for that orbit.

Lesson Notes

Student guidance and lesson notes

Overview

This lesson sets up the whole topic, so the diagrams need to do most of the work. Keep the rotation, orbit, tilt, and viewing direction clear at every stage so you can explain the patterns they see in the sky rather than memorising them as separate facts.

What You Need to Know

Model the Earth rotating once every 24 hours and use this to explain why the Sun appears to move across the sky and why day and night alternate.
Keep the Earth’s axis tilt visible when teaching seasons so you link changing sunlight angle and day length to the yearly orbit.
Use a simple top-down and side-view Moon model to show that phases are caused by the changing view of the illuminated half of the Moon during its orbit.
Use average orbital speed as a distance-over-time calculation with clear units.
Keep relative timescales visible: one day for rotation, one month for the Moon’s orbit, and one year for the Earth’s orbit.

How to Work Through It

Start with a sky-observation prompt on sunrise, sunset, and the changing appearance of the Moon.
Work through Earth’s rotation and orbit using annotated diagrams or a physical model, then connect these motions to day and night and the seasons.
Build the Moon phase model step by step, making you identify the Sun, Earth, Moon, and the illuminated side at each position.
Finish with one short average-orbital-speed calculation and a mixed explanation task on the Earth-Moon system.

Check Your Understanding

Check whether you can decide whether day and night are caused by the Earth’s rotation or by the Earth’s orbit, and give a reason.
Use a hinge question where you identify which season a hemisphere experiences when tilted towards the Sun.
Try one Moon-phase diagram and check whether you can explain why only part of the Moon appears lit from Earth.

Common Mistakes

Saying the seasons are caused by the Earth being closer to the Sun. Keep the axis tilt and sunlight angle central to every explanation.
Some think the Moon’s phases are caused by the Earth’s shadow. Contrast phases with eclipses so the difference is explicit.
You may confuse rotation with orbit. Keep the three main cycles on the same summary diagram so their timescales are easy to compare.

Next Steps

Set retrieval questions that compare the three repeating cycles and their causes.
Carry forward the ideas of orbit, gravity, and scale into the next lesson on the Solar System.