1. Natural Sciences Grade 7
Term 4: Planet Earth and Beyond
Relationship of the Moon to the Earth

2. Topic 2 Relationship of the Moon to the Earth
Relative positions
Natural Sciences - Grade 7

3. The relative positions of the Moon, the Earth and the Sun
The force of gravity is directed to the centre of the Sun as the Earth revolves around the Sun.
The figure shows how the Earth orbits the Sun, how the Earth rotates and how the Moon orbits the Earth.
It is important that the learners have a good understanding of the Earth, the Sun and the Moon’s positions.
If they understand, then they will have a better concept of gravity as well as the tides.
As the Earth revolves around the Sun, the Moon revolves around the Earth’s orbit.
Natural Sciences - Grade 7

4. Natural Sciences - Grade 7
Earth’s orbit [learners do a practical demonstration of the Earth’s orbit
Revise vocabulary:
diameter [Straight line passing through the centre of a ball shape/circle from the one side to the other side].
lunar eclipse [Occurs when the Moon passes directly behind the Earth into its umbra (shadow). This can occur only when the Sun, Earth
and Moon are aligned exactly, or very closely with the Earth in the middle.
Earth's orbit  [The path in which the Earth travels around the Sun. The average distance between the Earth and the Sun is  million kilometres].
Natural Sciences - Grade 7

5. The relative position of the Moon to the Earth
Natural Sciences - Grade 7

6. Natural Sciences - Grade 7
Earth’s Rotation
Natural Sciences - Grade 7

7. Earth, Moon and Sun Positions During Lunar Phases
Natural Sciences - Grade 7

8. Natural Sciences - Grade 7
Moon phases [1-4]
New moon Waxing Crescent Moon
First Quarter Waxing Gibbous Moon
Phase 1 - New Moon - The side of the Moon that is facing the Earth, is not lit up by the sun. At this time the Moon is not visible.
Phase 2 - Waxing Crescent - A small part (less than 1/2) of the Moon is lit up at this point. The part that is lit up is slowly getting bigger.
Phase 3 - First Quarter - One half of the Moon is lit up by the Sun at this point. The part that is lit up is slowly getting bigger.
Phase 4 - Waxing Gibbous - At this time half of the Moon is lit up. The part that is lit is slowly getting bigger. Waxing means to slowly get bigger.
Natural Sciences - Grade 7

9. Natural Sciences - Grade 7
Moon phases [5-8]
Full moon Waning Gibbous Moon Last Quarter Waning Crescent Moon Moon
Phase 5 - Full Moon - The side of the Moon that is lit up by the Sun is facing the Earth. The entire Moon is lit up at this point.
Phase 6 - Waning Gibbous - The Moon is not quite lit up all the way by sunlight. The lit part of the Moon is slowly getting smaller. Waning means to slowly get smaller.
Phase 7 - Last Quarter - Half of the Moon is lit up but the Sun. The lit up part that we can see, is slowly getting smaller.
Phase 8 - Waning Crescent - A small part of the Moon is lit up at this point. It gets smaller by the minute.
Natural Sciences - Grade 7

10. Natural Sciences - Grade 7
8 Moon phases
Crescent refers to the phases where the Moon is less than half illuminated.
Gibbous refers to phases where the moon is more than half illuminated.
Sunlight is shown coming in from the right.
The Earth, is at the centre of the diagram.
The Moon is shown at 8 key stages during its revolution around the Earth.
The Moon phase name is shown alongside the image.
Exactly one half of the Moon is always illuminated by the Sun.
Certain times both the sunlit portion and the shadowed portion is visible and it creates the various Moon phase shapes.
The Moon’s shadow cannot be seen with the naked eye.
The diagram is only meant to demonstrate how the phases work.
The small inner Moons in the diagram do not show the fact that the same side of the Moon always faces Earth.
Natural Sciences - Grade 7

11. Natural Sciences - Grade 7
Basic characteristics of the Earth, Moon and Sun[Preston convert miles to km]
Size [circumference]
Position
Age
Make-up
Earth km
3rd planet from the Sun
4,6 billion years
water/ oxygen/ Rocky
Moon km
Satellite of Earth
Rocky
Sun km
Centre
Average sized yellow star
Let the learners calculate the difference in the size of the Moon and the Earth.
Do likewise with the Moon and the Sun as well as the Sun and the Earth.
Natural Sciences - Grade 7

12. Natural Sciences - Grade 7
Diameter of the Sun
The relative size of the Sun, Earth and Jupiter.
The Earth is the tiny blue spot seen next to Jupiter.
The diameter of the Sun is about 109 times larger than that of the Earth.
Natural Sciences - Grade 7