I have a theorhetical question about the Moon ..

[Tink_Archived]

Ok as we all know the Moon doesn't rotate ... it just has a bit of a little wobble and we always get pretty much the same view of it.

BUT ....

What if the Moon was to rotate

What effect would that have on the Earth ie tides, gravity etc etc

[lukebl]

The moon does rotate. It just happens to rotate at the same period as its orbit round the earth (or, rather, its orbit round the barycentre)

[Geno]

The moon does rotate. It just happens to rotate at the same period as it's orbit round the earth.

Which is why we always see the same side

[Keiran]

I dont know much about the moon, but if it does rotate what would happen if it stopped? Is that what helps keep it in its orbit?

[lukebl]

I dont know much about the moon, but if it does rotate what would happen if it stopped? Is that what helps keep it in its orbit?

Isn't that one of those "what if" questions about something that will never, and can never, happen?

[SeedyF]

And the reason we see a slightly different view (libration is rhe effect) is that the moon travels faster or slower relative to the earth because its orbit is an elipse. So sometimes it will rotate more or less.

I guess the question is what effect would there be if the moon wasnt locked tidally? I dont think that would have any effect on the tides not so confident about gravity though.

[SeedyF]

And if the moon is moving away from earth at 4cm a year how long will it be before its far enough away for tidal locking to be lost? Worse still when will it stop keeping the earths tilt etc steady

[Skills]

I don't think the rotation (or not) of the moon makes any difference to the gravitational effects the earth experiences from it.

[Tink_Archived]

The moon does rotate. It just happens to rotate at the same period as its orbit round the earth (or, rather, its orbit round the barycentre)

I knew what I meant LOL just didnt word it right..

[Tink_Archived]

And if the moon is moving away from earth at 4cm a year how long will it be before its far enough away for tidal locking to be lost? Worse still when will it stop keeping the earths tilt etc steady

and will that 4cm distance slowly accelerate year upon year as it gradually moves further from the earth ??

[SeedyF]

and will that 4cm distance slowly accelerate year upon year as it gradually moves further from the earth ??

[Keiran]

And if the moon is moving away from earth at 4cm a year how long will it be before its far enough away for tidal locking to be lost? Worse still when will it stop keeping the earths tilt etc steady

By the time this happens will the sun have engulfed us or will the enviroment on earth have changd so much that it will be unable to support human life???

[brantuk]

"(Earth) will be unable to support human life??? "

It's barely able to right now with all these cuts lol

[Keiran]

"(Earth) will be unable to support human life??? "

It's barely able to right now with all these cuts lol

[perrin6]

The moon's axial rotation has been 'captured' by Earth, I don't know how that happens exactly though,

Alan

[The Warthog]

I read during the 'what ia a planet?' debates that in a million or so years the barycentre of the Earth-Moon system will lie outside the surface of the Earth, thereby making the Moon a planet under the IAU definition. The rotational velocity of an object will make no difference to its gravity, as gravity is a function of mass.

[k8e]

Which is why we always see the same side

so, depending on what part of the world you live in you will always see that side?? coz we see 'the man in the moon' and so does america, surely they would see the back of what we see?

[JordanT]

Just wait untill i've done a bit more about gravity and space in physics and i'll answer it

[Moonshane]

so, depending on what part of the world you live in you will always see that side?? coz we see 'the man in the moon' and so does america, surely they would see the back of what we see?

no, everyone sees the same side. the moon rotates once for every orbit around the Earth so the same side always faces all of the Earth (approximately). it's a bit like one of those lazy knobs (brodie knobs???) on a steering wheel. imagine you are holding it and turn the steering wheel one revolution; your hand/the knob never changes position but relative to the bolt that holds it on the steering wheel it has turned a single revolution.

[brantuk]

Good analogy Shane! Also - we see about 55% of the moon due to the wobble effect - the dark side that we don't see is about 45% of the moons surface if I remember rightly. We see just a little bit around each side depending on which way the wobble is.

[The Warthog]

Good analogy Shane! Also - we see about 55% of the moon due to the wobble effect - the dark side that we don't see is about 45% of the moons surface if I remember rightly. We see just a little bit around each side depending on which way the wobble is.

This is called 'libration', and is shown on the VMA Moon Atlas, among others.

[AndyG63]

and will that 4cm distance slowly accelerate year upon year as it gradually moves further from the earth ??

I don't think so - that recession is the result of the Moon slowing the Earth's rotation down. There should come a point when both will lock to each other, though whether the Moon'll be outside the Earth's Hill Sphere by then (and therefore just wander off) or the sun will have gone all red giant, I dunno!

Andy

[matteboy]

What is gonna do ya head in next is that the moon is 400 times smaller than the sun and 1/400th the distance so we get a total solar eclipse, amazing coincidence eh, now I'm thinking if the orbit of the moon is not perfectly circular and the moon is sometimes closer in it's orbit and somtimes further away so we can see the 55% of it, does it depend where it is in its orbit as to how much of the eclipse we see, or if it's further away do we not get a total eclipse... ...ahh B@@@cks my brain's hurting, now stop thinking Matt...........

[The Warthog]

What is gonna do ya head in next is that the moon is 400 times smaller than the sun and 1/400th the distance so we get a total solar eclipse, amazing coincidence eh, now I'm thinking if the orbit of the moon is not perfectly circular and the moon is sometimes closer in it's orbit and somtimes further away so we can see the 55% of it, does it depend where it is in its orbit as to how much of the eclipse we see, or if it's further away do we not get a total eclipse... ...ahh B@@@cks my brain's hurting, now stop thinking Matt...........

If the Moon is a little further away during an eclipse, such as the eclipse I watched 30 miles away from my home in '94 or thereabouts, we get an annular eclipse because the moon appears smaller than the sun, and leaves a ring of light at totality.

The Moon is indeed almost the same size as the sun, and its orbit is such that eclipses are a fairly frequent occurrence, and the full Moon lasts all night whether in winter or in summer. It is also large enough to create tides which aided in the transition from sea borne life to land borne life. Makes me think that God did a pretty spectacular job of getting a planet ready for us.

[tinvek]

also don't get confused by the phrase "dark side of the moon", unless you're into pink floyd there is no constant dark side of the moon, when it's a "full" moon the side we can't see is the "dark side", when it's a "new" moon, the side we see is the "dark side" but the side we can't see is fully lit by the sun