Will the Moon eventually Escape Earths Clutch?

[a lone wolf]

well, the Moon is slowing getting father away from the Earth, so will it ever hit a point where it is no longer gravitionally attached to earth before the sun eats the planet?

 

[Saiph]

That could happen, should the earth have enough angular momentum to transfer to the moon. <br /><br />However, simulations show that it will come to a halt at either 50 or 70 day orbits (and the earth's "day" will be 50 or 70 current days long). Why the range? Simple, I can never remember the figure. <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>

 

[alpha_taur1]

That must theoretically occur well after the Earth is engulfed by the Sun when it expands to red giant. I think that's due to happen in about 5-7 Billion years? <br /><br />I seem to remember reading that the day was about 23 hours long during Triassic times and about 18 hours long 1 billion years ago. I make it around a 50 day orbit about 5 billion years hence. Considering that the Solar system is only around 4.5 billion years old, that's a fair way off. <br /><br />You can derive a differential equation based on the dissipation of energy by tidal friction). You basically derive a function describing the rate of change of the semi-major axis of the Moon's orbit as a function of time. The tides raised on the Earth by the moon dissipate energy (from friction) due to tidal oscillations caused by the fact the Moon orbits in a different period than the Earth rotates. The result is a corresponding phase shift of the Earth's tidal response.<br /><br />I'm delving a bit outside my field, so please feel free to correct me.

 

[vogon13]

Isaac Asimov in one of his many fine science essays discussed a relevant topic to this. By his calculation, the moon is essentially in a solar orbit that is modified somewhat by earth. He compared the strength of the gravitational pull between the sun and the moon, and earth and the moon, and noted force from sun was roughly twice that from earth.<br /><br />So it already happened!<br /><br />And I suppose later tonight I am going to spend an hour not finding the relevant article in my poorly organized library. Believe title of essay or recurring theme was tug-of-war values. Virtually all satellites in solar system except earth's moon are 'held' tighter by their respective planets than by the sun. <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[Saiph]

gotta make this brief but:<br /><br />Alpha: It's a good start. The catch is figuring out what the equation is, as the tidal forces will diminish as the moon receeds. Not impossible, but a little trickier than you'd think.<br /><br />vogon: That is correct, I could do some calculations to show you what's up, but I don't have time (or the source actually).<br /><br />If you look up "Roche Instability Limit" you should end up with it.<br /><br />Ciao! <div class="Discussion_UserSignature"> <p align="center"><font color="#c0c0c0"><br /></font></p><p align="center"><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">--------</font></em></font><font color="#999999"><em><font size="1">----</font></em></font><font color="#666699">SaiphMOD@gmail.com </font><font color="#999999"><em><font size="1">-------------------</font></em></font></p><p><font color="#999999"><em><font size="1">"This is my Timey Wimey Detector.  Goes "bing" when there's stuff.  It also fries eggs at 30 paces, wether you want it to or not actually.  I've learned to stay away from hens: It's not pretty when they blow" -- </font></em></font><font size="1" color="#999999">The Tenth Doctor, "Blink"</font></p> </div>

 

[rogers_buck]

No, eventually there will be a giant tether dangling all the way to the earth. The traffic on the tether will pull the moon down.

 

[thalion]

Probably not. In fact, according to one book I've read (The Life and Death of Planet Earth), it will actually spiral in towards Earth once the Sun turns into a red giant, due to friction from the much denser interplanetary medium. It may even crash on the surface, though everything will be long dead by then...