moon is going away

[chitrangda]

hi!

moon is going away 4m earth!a time will come when there will be no moon revolving around earth.how strange?isint it?

can any one explain what will be harmfull effects of that?

i know only one that is we'll not have any tides!

pls rply:-)

[swansont]

Absent some outside interaction, the moon will not escape from the earth, since it is gravitationally bound. The current situation, of receding ~ 4cm per year, is transfer of energy and angular momentum because of tidal interactions ("tidal friction"), which is responsible for the slowing of the earth's rotation and the main reason we have leap seconds. Once the earth becomes tidally locked to the moon, they will face each other with no relative rotation, and the moon will not recede anymore. At that point, energy losses will cause the moon to get closer to the earth.

[Dr. Dalek]

Once the earth becomes tidally locked to the moon,

How long from now is it believed that this "tidal locking" will happen?

[swansont]

How long from now is it believed that this "tidal locking" will happen?

 

 

Billions of years. The sun will expand and toast us before it would happen.

[Anjruu]

Is this tidal locking theorized, or do we have actual examples of this?

 

"Once the earth becomes tidally locked to the moon, they will face each other with no relative rotation, "

 

What? So the moon would not orbit, but would rather stay over the same spot on the earth? Like a geosynchronous satellite? Funky...

[J.C.MacSwell]

Is this tidal locking theorized' date=' or do we have actual examples of this?[/b']

 

"Once the earth becomes tidally locked to the moon, they will face each other with no relative rotation, "

 

What? So the moon would not orbit, but would rather stay over the same spot on the earth? Like a geosynchronous satellite? Funky...

 

The moon is tidally locked to the Earth. Mercury to the sun. I suspect there are examples of mutually locked.

[Severian]

The moon is tidally locked to the Earth. Mercury to the sun. I suspect there are examples of mutually locked.

 

The tidal lock of the moon to the Earth (which we already have) is not the same thing as the Earth being tidal locked to the moon.

 

Edit: rereading your post, I think it is evident that you knew that already. Sorry for being patronising.

[swansont]

The moon is tidally locked to the Earth. Mercury to the sun. I suspect there are examples of mutually locked.

 

Mercury is at a 3:2 resonance, though, so it's not one side always facing the sun. It's stable because of the eccentricity of the orbit.

 

Pluto and Charon are tidally locked to each other.

[CPL.Luke]

how can we know that pluto and charon are tidally locked together? it was my understanding that we could barely make ut any of the features on pluto.

[GutZ]

Is angular momentum just another way for saying rotation?

[J.C.MacSwell]

Is angular momentum just another way for saying rotation?

 

The momentum of rotation.

[swansont]

how can we know that pluto and charon are tidally locked together? it was my understanding that we could barely make ut any of the features on pluto.

 

From http://www.solarviews.com/eng/pluto.htm

 

"During the period from 1985 through 1990, Earth was aligned with the orbit of Charon around Pluto such that an eclipse could be observed every Pluto day. This provided opportunity to collect significant data which led to albedo maps defining surface reflectivity, and to the first accurate determination of the sizes of Pluto and Charon, including all the numbers that could be calculated therefrom."

 

Perhaps the rotation data came from that

[chitrangda]

Stop scaring the Moon. We'll need her later.

very funny.how do u know that moon is she?

[Dr. Dalek]

very funny.how do u know that moon is she?

In greek, and possibly celtic myth, the moon was usualy depicted as a woman.

Diana, would be a good example.

[Callipygous]

im confused, what exactly does tidally locked mean? just that the same side would always be visible from the other? if so, would the earth still be rotating, just at the same rate that the moon is orbiting, or would they both be stationary, just orbiting the sun?

 

 

btw, this: 4m is the most rediculous example of internet shorthand i have ever seen. the time it saves you, compared to the time it costs people on the other end to figure out what the bloody hell it means borders on rudeness. if you used it to mean "form" it would be a different story. : P

[Sisyphus]

The moon is already tidally locked to the Earth. It just means the same side of the moon is always facing the Earth. When the Earth becomes tidally locked to the moon, the vice versa will be true. i.e. the same side of the Earth will always face the moon, and the moon will not appear to move in the sky at all. They would still orbit one another, but they would both be rotating at the same speed, which is in turn the speed of revolution about each other. Kind of like as if there was a giant tether holding them together.

[swansont]

And to continue Sisyphus's answer, the reason for the locking is that the tidal deformations do not lie along the axis between the respect center of masses, so there are torques exerted that allow angular momentum transfer (a force along the axis would not allow this). So over time the moon lost rotational angular momentum and now has one side — the more massive side — facing us, and only rotates once per orbit.

[chitrangda]

r u poeple shure abt it?

[swansont]

r u poeple shure abt it?

 

I have to protest. I can excuse typos and legitmate spelling errors, but unless you are actually posting from your phone, there is no freaking excuse for "texting" instead of typing out words. This isn't a chat room, and you're not sitting at the kids' table. Please act appropriately.