gravity...

[titanium22]

<p>&nbsp;</p><p><font size="2">I have often wonder how gravity works and what all is involved in it's complexity, or maybe simplicity?</font></p><p><font size="2">How come for starters the massive gravitation field that exist around large objects say Jupiter & Saturn for starters dose not pull everything around it into it? Space debris, comets, asteroids and even there own moons? What force keeps them away form this consistent pull?</font></p><p><font size="2">Also what is the&nbsp;force that is moving our own moon away from us by about 2" a year? with the tug the earth and moon put on each its hard to believe this is happing..</font></p> <div class="Discussion_UserSignature"> <p> </p><p><font size="1" color="#333399"><em>...and the search for life and earth like planets continues.</em></font></p> </div>

 

[origin]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;How come for starters the massive gravitation field that exist around large objects say Jupiter & Saturn for starters dose not pull everything around it into it? Space debris, comets, asteroids and even there own moons? What force keeps them away form this consistent pull?</DIV></p><p>Comets and the like do hit&nbsp; Jupiter and&nbsp;Saturn.&nbsp;&nbsp;In fact everytime you see a 'shooting star' that is some cosmic debris falling to earth due to gravity.&nbsp; The simple reason why the moons do not fall into&nbsp;Jupiter is because they are moving.&nbsp;&nbsp;The moons want to move in a straight line but the gravity of the planet pulls them towards it so that they are&nbsp;in a perpetual state of&nbsp;freefall.&nbsp; This is the same reason that the space station stays in orbit and there appears to be&nbsp;no gravity (they are in free fall).&nbsp; If you slow down the space station or a moon it will move towards the planet, if you slow it down enough&nbsp;it will plumet to the planet.&nbsp;</p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Also what is the&nbsp;force that is moving our own moon away from us by about 2" a year? with the tug the earth and moon put on each its hard to believe this is happing.. <br />Posted by titanium22</DIV></p><p>This is a little more complicated but it is the same idea - orbital velocity.&nbsp; The moon's gravity&nbsp;causes tides and the tides are also moved by the rotation of the earth (which is about 30 times faster than the moons rotation).&nbsp; The moon orbits in the same direction as the earth rotates.&nbsp; What this does is it makes the tides precede the moon slightly.&nbsp; This results in a transfer of momentum from the earth to the moon.&nbsp; You can look at it like the bulge of the tide preceding the moon is pulling the moon forward.&nbsp; So the upshot is that the moons orbital velocity increases which means that it moves farther from the Earth.&nbsp; If enough momentum is transfered the moon will leave the earths orbit.&nbsp; </p><p>Frankly, I don't know if the moon will&nbsp;leave earths orbit&nbsp;in the far future or not.</p> <div class="Discussion_UserSignature"> </div>

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Frankly, I don't know if the moon will&nbsp;leave earths orbit&nbsp;in the far future or not. <br /> Posted by origin</DIV></p><p>&nbsp;</p><p>I don't believe it will.&nbsp; For the same reasons you cited above, the conservation of angular momentum between the two bodies means that the Earth's rotation is also slowing down during this process.&nbsp; The moon being behind the bulge gradually tugs on it and slows the rotation down.&nbsp; We will eventually become tidally locked with the moon the same as pluto/charon.&nbsp; When this happens, there will be no transfer of angular momentum to increase the moon's orbital velocity.</p><p>The Sun, to a lesser degree, is also affecting the Earth in the same way.&nbsp; The Earth will eventually rotate once per orbit about the sun.&nbsp; Not really sure what happens at this point with the moon.&nbsp; Maybe falls into a somewhat stable (not considering perturbations from other planets) L1 orbit between the Sun and Earth?&nbsp; Anyone know?&nbsp;</p><p>Of course, by the time this happens, we won't be living on Earth to witness it.&nbsp;</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[MeteorWayne]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;&nbsp;In fact everytime you see a 'shooting star' that is some cosmic debris falling to earth due to gravity.&nbsp; Posted by origin</DIV><br /><br />Just wanted to clarify this a bit. While gravity does influence shooting stars, they actually&nbsp;hit the earth due to the fact that we intersect their orbit around the sun. Objects orbiting the sun at 1 AU (the earth's distance) are moving between 30 and 41 km/sec (60,000-100,000 mph) on their own orbit. The earth's relativeily weak gravity does increase the speed of meteoroids that hit us, but is too weak to alter their paths much to "suck them in" if they were not already going to hit us.</p><p>MW</p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[lukman]

Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;We will eventually become tidally locked with the moon the same as pluto/charon.</DIV><br /><br />I thought we are tidal locked already now? <div class="Discussion_UserSignature"> </div>

 

[MeteorWayne]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I thought we are tidal locked already now? <br />Posted by lukman</DIV></p><p>The moon is tidally locked to the earth now. Eventually, the earth will become tidally locked to the moon as well, so only half the earth will be able to see it.<br /></p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I thought we are tidal locked already now? <br /> Posted by lukman</DIV></p><p>The Moon is tidally locked with the Earth. The Earth is not tidally locked with the Moon... yet.&nbsp; The process of synchronization is not complete.&nbsp;</p><p>&nbsp;</p><p>Edit:&nbsp; MW beat me to it... Gotta be quick when you're on.</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>

 

[origin]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Just wanted to clify this a bit. While gravity does influence shooting stars, they actually&nbsp;hit the earth due to the fact that we intersect their orbit around the sun.<br />Posted by MeteorWayne</DIV></p><p>&nbsp;Absolutely right.&nbsp; My reply was misleading and not correct.&nbsp; Any satelites and man made debris in space that falls to earth is a much more accurate way to make the point I was trying to make.</p><p><br /><br />&nbsp;</p> <div class="Discussion_UserSignature"> </div>

 

[astralith]

<p>What keeps the planets from falling into the sun or moons from falling to planets?</p><p>Nothing!</p><p>They just always miss </p>

 

[MeteorWayne]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>What keeps the planets from falling into the sun or moons from falling to planets?Nothing!They just always miss <br />Posted by astralith</DIV></p><p>&nbsp;</p><p>Exactly. That's what an orbit is.</p><p>Going just fast enough to miss all the time.<img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-cool.gif" border="0" alt="Cool" title="Cool" /><br /></p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[drwayne]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;Exactly. That's what an orbit is.Going just fast enough to miss all the time. <br />Posted by MeteorWayne</DIV></p><p>Or, another picture is this - an object in orbit arround Earth is falling towards Earth at the same rate as the Earth's surface is falling away from it as it moves around it.</p><p><br /><br />&nbsp;</p> <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[thebigcat]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Or, another picture is this - an object in orbit arround Earth is falling towards Earth at the same rate as the Earth's surface is falling away from it as it moves around it.&nbsp; <br />Posted by drwayne</DIV></p><p>&nbsp;</p><p>Uh......</p><p>&nbsp;</p><p>....</p><p>&nbsp;</p><p>...</p><p>&nbsp;</p><p>Anyway, this brings to mind Douglass Adams's comment about the secret to flying being that one merely throws one's self at the ground and misses.<br /></p> <div class="Discussion_UserSignature"> </div>

 

[drwayne]

<p>Unclear what your response meant.</p><p>The Earth's surface is of course curved.&nbsp; If you were to follow a straight line that initially started at a cetrain altitude, the Earth's surface would appear to curve away from you as you moved along the tangent line. </p><p>In an circular oribital trajectory, you are falling at the same rate as the Earths surface falls away from you, so you maintain a constant altitude.</p><p>Wayne</p> <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[dragon04]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;<font color="#993300"> Frankly, I don't know if the moon will&nbsp;leave earths orbit&nbsp;in the far future or not. <br /> Posted by origin</font></DIV></p><p>IN fact, it won't, If it were given the time by the Sun not going red giant, in 15 billion years, the Moon's orbit would stabilize at about 1.6 times its current distance.</p><p>There's a pretty interesting article at this URL:</p><p>&nbsp;</p><p>http://www.aerospaceweb.org/question/astronomy/q0262.shtml</p> <div class="Discussion_UserSignature"> <em>"2012.. Year of the Dragon!! Get on the Dragon Wagon!".</em> </div>

 

[Philotas]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The moon is tidally locked to the earth now. Eventually, the earth will become tidally locked to the moon as well, so only half the earth will be able to see it. <br />Posted by MeteorWayne</DIV><br /><br />Hmm, moon tourism just got a new meaning.</p> <div class="Discussion_UserSignature"> </div>

 

[MeteorWayne]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Hmm, moon tourism just got a new meaning. <br />Posted by philotas</DIV></p><p>&nbsp;</p><p>LOL, the moon will be a charcoal briquet well before then <br /></p> <div class="Discussion_UserSignature"> <p><font color="#000080"><em><font color="#000000">But the Krell forgot one thing John. Monsters. Monsters from the Id.</font></em> </font></p><p><font color="#000080">I really, really, really, really miss the "first unread post" function</font><font color="#000080"> </font></p> </div>

 

[Philotas]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp;LOL, the moon will be a charcoal briquet well before then <br />Posted by MeteorWayne</DIV><br /><br />Hehe! Well that is too bad, I already envisioned what such a world would be like, and for no use. <img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-cool.gif" border="0" alt="Cool" title="Cool" /></p> <div class="Discussion_UserSignature"> </div>

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>IN fact, it won't, If it were given the time by the Sun not going red giant, in 15 billion years, the Moon's orbit would stabilize at about 1.6 times its current distance.There's a pretty interesting article at this URL:&nbsp;http://www.aerospaceweb.org/question/astronomy/q0262.shtml <br /> Posted by dragon04</DIV></p><p>&nbsp;</p><p>I mentioned in an earlier post that the orbital recession will stop when they are both tidally locked and the transfer of momentum ceases, but to take it a step further...</p><p>What happens to the moon when the earth becomes tidally locked with the sun?&nbsp; Will the moon fall into an orbit within the earth/moon Lagrange point 1 (L1)?</p><p>&nbsp;</p><p>Edit:&nbsp; I put some thought into it and realized that when the earth and moon become tidally locked, the sun's tidal effects on the earth will progressively try to slow the earth's rotation down.&nbsp; This would cause the moon to orbit the earth faster than the earth rotates, thus reversing process and transferring momentum from the moon back to the earth.</p><p>It would seem at this point, the process becomes irreversible until the moon crashes into the earth or the orbit becomes unstable and the moon is flung from its orbit as its acceleration increases.</p><p>Maybe i'm just too tired and overthinking it...&nbsp;</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>