0 ratiation planet

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chebby

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Is there a planet in our solar system that is always facing the same side of the sky (does not rotate at all) or at least has a very large rotation period?<br /><br />I was just thinking if there would be an out of system dense meteor shower for many days or weeks, that would be the kind of planet I would want to be on to avoid getting hit.
 
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odysseus145

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Venus has a rotaional period of 243 days which is the longest of any planet. I don't know about moons though. <div class="Discussion_UserSignature"> </div>
 
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tom_hobbes

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Had to comment on the quality sig-line. Very cute! <img src="/images/icons/smile.gif" /> <div class="Discussion_UserSignature"> <p><font size="2" color="#339966"> I wish I could remember<br /> But my selective memory<br /> Won't let me</font><font size="2" color="#99cc00"> </font><font size="3" color="#339966"><font size="2">- </font></font><font size="1" color="#339966">Mark Oliver Everett</font></p><p> </p> </div>
 
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petepan

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Tickled my funny bone too when i first saw it (the sig-line) in another thread. LOL <img src="/images/icons/smile.gif" />
 
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mooware

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<font color="yellow">"I was just thinking if there would be an out of system dense meteor shower for many days or weeks, that would be the kind of planet I would want to be on to avoid getting hit"</font><br /><br />Well, you would avoid being hit if you were on the opposite site of the planet, but then you would likely suffer after effects of the strikes. As it would cause global devistation.<br /><br />
 
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CalliArcale

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Plus, although the pretty but basically harmless meteor showers such as the Perseids do <i>predominantly</i> strike the leading side of the planet, they aren't limited to it, and more dangerous meteorites can come from any direction at all. <img src="/images/icons/shocked.gif" /> It's not the meteor showers you have to worry about -- it's the isolated minor planets (asteroids, comets, etc) with orbits that cross the orbit of your own planet that have the potential to cause major devastation.<br /><br />Now as to the first question....<br /><br />Is there a planet which rotates synchronously, as the Moon rotates synchronously? (Note: such objects DO rotate. It's just that they take the same amount of time to rotate as they do to complete one orbit, so they always face the same side to their parent.) For a long time, Mercury was believed to rotate synchronously, but the advent of doppler radar techniques in the 60s disproved that. It <i>does</i>, however, have a resonance between its rotational period and its orbital period -- for every three Mercury days, there are exactly two Mercury years. It is the only body ever discovered with a rotational-to-orbital resonance other than 1:1 (which is synchronous).<br /><br />Lots of moons are synchronous, however, including our Moon, Io, Europa, Ganymede, Callisto, almost all of Saturn's moons with known rotational periods (apart from Phoebe and Hyperion, which are probably captured asteroids), and Pluto's moon Charon. Charon is actually very interesting case. Like our Moon, it is very large relative to its parent body, which means it has a significant tidal effect on its parent. Over time, Pluto and Charon have become <i>mutally synchronous</i> -- they always face one another. One Pluto day, one Charon day, and one Charon "month" are all the same length. An observer on Pluto would see Charon fixed motionless in the sky while the stars wheeled past in the background and Charon went through its phases. Someday in the distan <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>
 
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chebby

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<i>Earth's day is gradually lengthening as rotational energy is transferred tidally into the Moon's orbirtal energy, pushing the Moon further away. </i><br /><br />Oh that's why. They mentioned the moon moving away on Nova yestereday, but they never explained why. Although I have a hard time trying to imagine the physics of it.
 
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Saiph

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I could've sworn there was another body (probably moon) with a resonance other than 1:1 with the primary. Or maybe that was a resonance with a perturber (similar to venus-earth) not the primary.<br /><br />Another neat fact: Venus is in resonance with the earth IIRC. It may even be a 1:1 so we always see the same side of venus.<br /><br /><br />The mechanism for the energy transfer to the moon is relatively simple.<br /><br />The moon causes tides, bulges in the earth (most noticable in the oceans). These bulges, however, have inertia and friction. So the moon pulls the ground up, but the earth rotates, moving the bulge out from under the moon.<br /><br />Now the bulge is "ahead" of the moon, and pulls the moon forward (the other bulge is behind, but further away so the backwards pull of gravity is less).<br /><br />Pulling an object forward in the orbit, adds energy, which results in the object moving further out. The cost of this transfer, however, is the loss of rotation for the earth (we spin slower).<br /><br />That's the brief basics. Of to Optics class! <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>
 
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nexium

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High chebby: As far as we know everything rotates with respect to the distant stars, but there might be an asteroid or comet that rotates less than once per century. Venus is much too hostile for present technology, but the poles of Mercury could be colonized in this decade at enourmous cost. Mercury has essentually no tilt on its axis, so the sun never shines on the bottom of creators near the poles of Mercury. There is negligible atmosphere to tranfer heat. The surface has been measured at -133 degrees, but a few humans would warm it to a comfortable temperature. The weak magnetic field would steer some ions into the colony, but shielding is likely practical. The poles of Mercury face the distant stars with little movement, so one pole or the other would have most of Mercury to protect the colony from radiation and incoming comets and asteroids. The poles of Mercury may be the safest location in our solar system in case of a nearby super nova or nova. Neil
 
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CalliArcale

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<blockquote><font class="small">In reply to:</font><hr /><p>Another neat fact: Venus is in resonance with the earth IIRC. It may even be a 1:1 so we always see the same side of venus. <p><hr /></p></p></blockquote><br /><br />You do recall correctly!<br /><br />According to the Nine Planets:<br /><br /><i>"Venus' rotation is somewhat unusual in that it is both very slow (243 Earth days per Venus day, slightly longer than Venus' year) and retrograde. In addition, the periods of Venus' rotation and of its orbit are synchronized such that it always presents the same face toward Earth when the two planets are at their closest approach. Whether this is a resonance effect or merely a coincidence is not known."</i> <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>
 
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pizzaguy

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<font color="yellow"><br />"Venus' rotation is somewhat unusual in that it is both very slow (243 Earth days per Venus day, slightly longer than Venus' year) and retrograde. In addition, the periods of Venus' rotation and of its orbit are synchronized such that it always presents the same face toward Earth when the two planets are at their closest approach. Whether this is a resonance effect or merely a coincidence is not known."</font><br /><br />Wasn't there a guy on Art Bell's show a while back that said he knew why? IIRC, it was because an alien race had a base there and were hiding from us. <img src="/images/icons/rolleyes.gif" /><br /><br />There are no mysteries or coincidences if you are kooky enough. <img src="/images/icons/laugh.gif" /> <div class="Discussion_UserSignature"> <font size="1"><em>Note to Dr. Henry:  The testosterone shots are working!</em></font> </div>
 
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zavvy

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<font color="yellow">Wasn't there a guy on Art Bell's show a while back that said he knew why? IIRC, it was because an alien race had a base there and were hiding from us.</font><br /><br />There's a guy scheduled for tonight who claims to have walked on The Moon... lol... <img src="/images/icons/wink.gif" /><br /><br />http://www.coasttocoastam.com/shows/2004/10/04.html<br /><br />
 
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