Download Moon`s rotation and revolution - E

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Just like the Earth and the planets rotate around an axis, the Moon also has an axis
around which it rotates. Its rotation takes 28 days. The Moon also revolves or orbits
around the Earth. One orbit also takes 28 days!
That means that the Moon’s rotation and revolution takes the same amount of time –
28 days!
This is why we only see one side of the moon. The rate or speed of the rotation
(spinning on its axis) is the same rate or speed of its orbit (around the Earth).
What does this mean?
This is a difficult thing to understand without seeing it in action. Work with a friend.
Cover a small polystyrene ball in aluminum foil. Push a skewer stick through it and
use the model you made of the Earth (polystyrene ball).
• One person must hold the Earth model still, while the other moves the Moon around it
• Whoever is moving the Moon should try to rotate (turn) the Moon around its axis at the same speed as he or she revolves it around the Earth
• Take note of a mark or feature on the Moon that is facing the Earth and follow it around as it rotates and revolves
You should ensure that the feature you took note of is always facing the Earth.
If the Moon did not rotate at the same speed as it revolves around Earth, we would
see other parts of the Moon. There is always a side of the Moon that we will not see,
except if a spacecraft photographs it.
© e-classroom 2014 www.e-classroom.co.za
GRADE 6
Grade 6 Natural Science and Technology: Movement of the Moon: The Moon’s Rotation and Revolution
Moon’s rotation and revolution
The Moon’s position in relation to the Earth and the Sun determines how much we
can see of it. At “New Moon”, the Sun shines on the Moon, but because of its position
to us we can’t see the reflection and so it looks “dark” to us. After this, the Moon
moves through its phases with more and more of the Moon reflecting the Sun as it
goes. At “full Moon” we are able to see the reflection of the whole side of the Moon.
Activity
Use the two polystyrene balls you’ve already made – one covered in foil and the
plain one, both with a skewer through them as their axis. You will also need a torch.
Make the classroom as dark as possible. Turn the torch on as the Sun. Use the
diagram above, of the Moon phases, to position the Earth and Moon in relation to
each other in each of its phases.
(NOTE: You may have to move the objects a distance from each other so that they do
not cast shadows on each other. Remember, in space, the Moon, Earth and Sun are
thousands of kilometers apart.)
© e-classroom 2014 www.e-classroom.co.za
GRADE 6
Grade 6 Natural Science and Technology: Movement of the Moon: The Moon’s Rotation and Revolution
We can only see the Moon because it reflects the light from the Sun. The part of the
Moon that we see is the part that is lit by the Sun. Look at this picture of the phases
of the Moon.