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I Spin or rotation of moon?

  1. Mar 15, 2017 #1
    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
  2. jcsd
  3. Mar 15, 2017 #2


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    You should try to simulate this using objects sitting on the table in front of you.
  4. Mar 15, 2017 #3
    Ya i did but rotation without changing the phase is possible? How and why?
  5. Mar 15, 2017 #4
    "Dark Part" ? - The times I read this "Dark Side" nonsense - The Moon experiences day and night just like the Earth.
  6. Mar 15, 2017 #5


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    I'm sorry, I'm having a little trouble understanding your post. Can you elaborate a little on what you did?
  7. Mar 15, 2017 #6


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    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:
    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.
  8. Mar 15, 2017 #7


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    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).
  9. Mar 15, 2017 #8


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    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

  10. Mar 16, 2017 #9
    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?
  11. Mar 17, 2017 #10


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    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.
  12. Mar 18, 2017 #11


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    Get yourself a rotating office chair. There are so many Astronomy Simulations you can do with it. If you also happen to have a football or tennis ball, you can really enjoy yourself. I remember getting a girl in a Science class to do pirouettes around the classroom to show the difference between Solar days and sidereal days. She enjoyed being the centre of attention and the (low ability) class were entertained and possibly enlightened a bit. RESULT!
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