Question

Is moon spinning? :D

Answer 1

Now we know that moon is tidally locked to earth. So we can look at it in two ways


we can say yea.. moon spins with same rotation period as the revolution period.

but we can also think of it as tying a string to a stone and whirling it around, in which case we don't say that the stone is spinning on its axis right?

Answer 2

@ikram002p

Answer 3

@ganeshie8 @aaronq @ParthKohli

Answer 4

i believe so , which is weird lol
first time to think about it hmm

Answer 5

It's a matter of choice of reference frame.
The Moon is rotating wrt distant stars or in the geocentrical or heliocentrical frames.

It is not spinning in the frame defined by the centres of Earth and Moon (similar to the frame of the string that ties the stone you mentioned), but that's not a frame that is of much use, I'm afraid.

Answer 6

@Vincent-Lyon.Fr
If u were asked is the moon in rotational motion or transnational motion .. i mean the moon as a rigid object..
since all the points on the moon are moving with exactly the same velocity (as seen by any reference frame) .. the moon is doing translation and not rotation .. so therefore no spin?! hows that argument? :D

Answer 7

Hi, it's not true that all points on the moon are moving with the same velocity.
Looked at from the centre of mass of the earth moon system, the visible side of the moon is moving with a lower speed than the far side, since v = omega r, where omega is the angular velocity and r is the distance from the centre of mass to a particular point.

Answer 8

I'm not sure if everyone would agree, but I think of 'spinning' as rotation about an axis within the body, whereas 'rotation' perhaps includes cases where the axis of rotation lies outside the body.
I think it's a great question. : )

Answer 9

quite right.. i like to rephrase what i said..

All points on the moon are have the same direction of the velocity :D..
yes.. so the question is.. "Whether moon is spinning?"

cause its just like stone tied to a string and whirled. You wouldn't say that the stone is SPINNING right?

but i think its just a matter of definition ..

and come to think of it.. the string and stone makes more sense.. people say, tidal locking.
but i think i understand it this way

imagine, you have a stone tied to a string.. and while you try to whirl it, imagine u try to make that stone spin on its own axis too. .. the string would immediately counter that, right? .. ergo tidal locking :D.

Answer 10

and we need to differentiate between ..

tidal locked revolution like the moon and the earth

and a revolution in which the moon wouldn't even spin
like this.. in this the weird pointed thing is not even spinning but it is revolving..