Talk:3753 Cruithne: Difference between revisions
Phil Boswell (talk | contribs) No, he means "an unusual orbit about '''the orbit of''' the Earth" |
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:NO IT DOESN'T! Have another look at the animation - even if you hold the Earth still, Cruithne KEEPS TO ONE SIDE of the Earth - it does not orbit AROUND the Earth. The horseshoe slowly migrates until it's edge comes close to the Earth, whereupon it reverses direction so that the effect can repeat itself with the other edge of the horseshoe after another 385 years (orbital inclination notwithstanding). There is a myth out there the Cruithne is a moon of the Earth, and I think everything possible needs to be done to kill this myth. (I know that Paul Wiegert says "The near-Earth asteroid 3753 Cruithne is in an unusual orbit about that of the Earth" - I think his choice of the word "about" is unfortunate, I think he probably means "in relation to"). |
:NO IT DOESN'T! Have another look at the animation - even if you hold the Earth still, Cruithne KEEPS TO ONE SIDE of the Earth - it does not orbit AROUND the Earth. The horseshoe slowly migrates until it's edge comes close to the Earth, whereupon it reverses direction so that the effect can repeat itself with the other edge of the horseshoe after another 385 years (orbital inclination notwithstanding). There is a myth out there the Cruithne is a moon of the Earth, and I think everything possible needs to be done to kill this myth. (I know that Paul Wiegert says "The near-Earth asteroid 3753 Cruithne is in an unusual orbit about that of the Earth" - I think his choice of the word "about" is unfortunate, I think he probably means "in relation to"). |
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::No, he means "an unusual orbit about '''the orbit of''' the Earth". HTH HAND --[[User:Phil Boswell|Phil]] | [[User talk:Phil Boswell|Talk]] 14:58, Dec 23, 2004 (UTC) |
::No, he means "an unusual orbit about '''the orbit of''' the Earth". HTH HAND --[[User:Phil Boswell|Phil]] | [[User talk:Phil Boswell|Talk]] 14:58, Dec 23, 2004 (UTC) |
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The article gives the average surface temperature of Cruithne as 378 Kelvin, that's well above the boiling point of water. How can that be for an object orbiting the sun at an average distance comparable to earths distance and without an atmosphere for any greenhouse effects? Does anyone have an explanation for this? [[User:84.160.196.181|84.160.196.181]] 14:23, 27 Feb 2005 (UTC) |
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Revision as of 14:23, 27 February 2005
"Cruithne shares Earth's orbit, but does not actually orbit the Earth. Instead, it follows a spiralling path that moves along the Earth's orbit in a horseshoe shape, the two ends of the horseshoe approaching either side of Earth but not quite reaching it. It takes Cruithne 385 years to complete one such horseshoe orbit."
- Not to sound stupid but I am not following this dicussion of Cruithne's orbit. Huh? :-) (I think we need to specify: horseshoe-shaped as observed from where?)
- Take a look at the diagrams and animation of Cruithne's orbit in the external link provided at the bottom of the page. If you can come up with a simple textual description of that, you are most welcome to replace the one above. :) -BD (Actually, since the images on the page are © Paul Wiegert, I'll email him and see if I can get permission to use them in Wikipedia. I don't think that a simple textual description is possible, period. :)
Good God! If I'm understanding that right, it IS horseshoe-shaped!!
- Well, only from the perspective of the Earth. From the perspective of an observer who isn't viewing the situation from a point orbiting the sun at Earth's orbital radius, Cruithne is actually following a relatively conventional elliptical orbit around the sun. But since that elliptical orbit has almost exactly the same period as Earth's, it behaves as if it's orbiting around the Earth in this weird manner. I've just emailed Dr. Weigert for permission to use some of his diagrams here, when I get a response I'll see about trying to explain this more clearly. It's cool. :) -BD
"a relatively conventional elliptical orbit", Okay, thanks, that restores my faith in God and Newton. :-)
- Not forgetting Kepler, if you please! - Lee M 01:28, 4 Sep 2003 (UTC)
"But since that elliptical orbit has almost exactly the same period as Earth's, it behaves as if it's orbiting around the Earth in this weird manner."
- NO IT DOESN'T! Have another look at the animation - even if you hold the Earth still, Cruithne KEEPS TO ONE SIDE of the Earth - it does not orbit AROUND the Earth. The horseshoe slowly migrates until it's edge comes close to the Earth, whereupon it reverses direction so that the effect can repeat itself with the other edge of the horseshoe after another 385 years (orbital inclination notwithstanding). There is a myth out there the Cruithne is a moon of the Earth, and I think everything possible needs to be done to kill this myth. (I know that Paul Wiegert says "The near-Earth asteroid 3753 Cruithne is in an unusual orbit about that of the Earth" - I think his choice of the word "about" is unfortunate, I think he probably means "in relation to").
The article gives the average surface temperature of Cruithne as 378 Kelvin, that's well above the boiling point of water. How can that be for an object orbiting the sun at an average distance comparable to earths distance and without an atmosphere for any greenhouse effects? Does anyone have an explanation for this? 84.160.196.181 14:23, 27 Feb 2005 (UTC)