# Spin or rotation of moon?

We all know we see only one part of moon means part which is facing towards earth
But moon rotates also so we should able to see its other part(dark part) but we cant.
I know rotational period of moon is equal to revolutionary period of moon but if moon is having rotational motion
So we should able to see other part

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russ_watters
Mentor
You should try to simulate this using objects sitting on the table in front of you.

Ya i did but rotation without changing the phase is possible? How and why?

"Dark Part" ? - The times I read this "Dark Side" nonsense - The Moon experiences day and night just like the Earth.

Drakkith
Staff Emeritus
Ya i did but rotation without changing the phase is possible? How and why?
I'm sorry, I'm having a little trouble understanding your post. Can you elaborate a little on what you did?

russ_watters
Mentor
Ya i did but rotation without changing the phase is possible? How and why?
The rotation of the moon and its phase are totally unrelated. The moon could rotate at any rate and the phases would look exactly the same in terms of what fraction of the moon is illuminated at what time. Also, from the OP:
...we should able to see its other part(dark part) but we cant.
Sure we can: the "dark part" is the part that isn't illuminated when we look at the moon on any day it isn't full.

If instead you mean the far side of the moon, which is totally different from "dark part", again, look at the objects sitting on the table in front of you. It should be easy to see how you can have the moon rotate once per revolution and therefore always have the same part facing the Earth.

1oldman2 and davenn
russ_watters
Mentor
"Dark Part" ? - The times I read this "Dark Side" nonsense - The Moon experiences day and night just like the Earth.
Right. The "dark part" changes once per [lunar] day just like on Earth. There is no "dark part" or rather, no part that is always dark (aka: dark side of the moon).

davenn
Gold Member
2019 Award
Ya i did but rotation without changing the phase is possible? How and why?
maybe not done quite right, as Russ said, the phases are unrelated to rotation on its axis
The moon rotates once on its access per 1 orbit of the earth, this is called Synchronous Rotation

have a look at this animation

you can see from looking down on the moon and earth from above that the moon does indeed rotate once on it's axis per orbit of the earth they do a couple of other examples of non-axial rotation and multiple axial rotations first

you can simulate this at home using a couple of balls one for earth and one for the moon. put a mark on the face, facing earth, of the moon ball and observe from above

Dave

1oldman2
So phase(side) of moon and rotation is not related,ok done.
Means synchronous rotation is exception case of rotation in which rotation does not depend on side we see am i right?

CWatters
Homework Helper
Gold Member
Means synchronous rotation is exception case of rotation in which rotation does not depend on side we see am i right?
Exception to what? All movement is relative.

Consider a merry-go-round. If you walk around one at the same speed as it rotates you will always see the same side. The merry-go-round appears stationary to you but it is still rotating with respect to the earth.

Viewed from the earth the moon always shows the same side (it appears stationary/not rotating), however viewed from the sun the moon can be seen rotating and there is no permanently dark side.

sophiecentaur