The Moon's rotation and revolution
How the Moon rotates and revolves, why we always see the same side, and the moon phases. Read one part at a time and tap “I know this”. Then test yourself in the quiz.
Know it already? Jump straight to the quiz
The chair test
Thabo walks once around a chair, always facing the chair. By the end his body has turned around once completely. In the same way the Moon spins once while it revolves once around the Earth. If the Moon did not rotate at all, we would see different sides in a month.
One spin for every lap = always the same face towards us.
Time on the Moon
- The Earth rotates about 27 times while the Moon revolves once.
- The Moon revolves around the Earth about 13 times a year; a quarter orbit takes about one week.
- On the Moon a place first gets very hot and then very cold: two weeks of sun, two weeks of dark, and no air.
- An astronaut on the near side sees the Earth stay in about the same place in the sky.
Sun, Earth and Moon compared
| Sun | Earth | Moon | |
|---|---|---|---|
| What is it? | A star | A planet | A moon (natural satellite) |
| Shape | Sphere | Sphere | Sphere |
| Made of | Very hot gases | Rock, with water and air | Rock and dust; no air |
| Size | The biggest: more than 100 Earths side by side | Smaller than the Sun, bigger than the Moon | About a quarter of the Earth’s width |
| Movement | Spins slowly on its axis | Spins on its axis (24 hours) and orbits the Sun (365¼ days) | Spins on its axis and orbits the Earth (about 27 days) |
| Makes own light? | Yes | No | No: it reflects sunlight |
The phases
From new moon to full moon takes about two weeks. At first quarter we see half the Moon lit, because it is a quarter of the way through the cycle. People all over the Earth, through the ages, have seen the same ‘face’ on the full moon.
From one new moon to the next takes about 29½ days, a little longer than the 27 days of one orbit, because the Earth also moves around the Sun in the meantime. That is why we say the Moon’s cycle is “about a month”.
Why does the Moon seem to change shape? The Sun always lights up half of the Moon. As the Moon revolves around the Earth, we see a different amount of that lit half: none of it at new moon, and all of it at full moon. The phases are not caused by the Earth’s shadow; the Earth’s shadow falls on the Moon only during a lunar eclipse.
Remember this and test yourself
- The Moon rotates once on its axis in about 27 days, and also revolves around the Earth in 27 days.
- Because it spins once for each trip around, we always see the same side.
- The far side of the Moon is not always dark; it was first photographed by a spacecraft in 1959.
- One day-and-night on the Moon lasts about a month: two weeks of sun, two weeks of dark.
- The Moon’s revolution makes the phases change; the Earth’s gravity keeps it in its orbit.
Write these points in your book. Read them again the night before the test.
The Moon is a shy dancer: it circles the Earth but always shows only its face, never its back.
Important words
First say what the word means, then turn the card over.
Match column A to column B
Tap a word in column A, then its meaning in column B. You can also start in column B.
True or false?
Read the question and the answer. Is the answer right? Tap True or False.
Now the real quiz!
The quiz has many more questions on this topic. Every question shows straight away whether you are right and explains why.
Take the quiz: The Moon's rotation and revolution- Read one part together and ask your child to tell it back in their own words.
- The ticks (“I know this”) are saved on this device only. We never ask for names or emails.
Follows CAPS for Grade 6 Natural Sciences and Technology. Always check your teacher’s notes and textbook too.