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#41
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Pluto is a planet again..
In article ,
Chris L Peterson wrote: IMO the decision to rigorously define "planet" was a solution looking for a problem (and in fact, created its own problems). The IAU definition of "planet" wasn't that rigorous really. First, it doesn't specify how large a deviation from the hydrostatic equilibirion shape is allowed for a body to still be considered a "planet". Some deviation is obviously allowed, or else the mountain ranges of the Earth would disqualify the Earth from being a planet. Second, the phrase "cleared its neighbourhood" is a quite fuzzy phrase, open for interpretation. -- ---------------------------------------------------------------- Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN e-mail: pausch at stockholm dot bostream dot se WWW: http://stjarnhimlen.se/ |
#42
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Pluto is a planet again..
On Mar 9, 11:00 pm, Greg Crinklaw
wrote: Chris L Peterson wrote: I understand the concept. I just think it fails miserably. There's no doubt in my mind that Pluto is a planet, as is Ceres and a number of other objects. Ah, ok, I see now. Why didn't you just come out and say from the start that you were among those disgruntled who cling to "Pluto is a planet?" You have neatly cut the question's significance down to where personal opinion can become of prime importance. Nicely done. Obviously there can be no further productive argument as this isn't a question of science, but rather of strongly held personal preference. personal preference. I really don't personally care one way or another. My interest is to find a reasonable way to keep the opinionated amongst us from squabbling forever! Hopefully it will be those like me who actually make the decision. Funny,funny,funny !. You could not a more comedic script than that surrounding the Pluto episode. Very early on one guy got in right and spotted the absurdity of it all and it becomes difficult to take you lot seriously after that ..It was those like you who made the decision ! http://groups.google.com/group/sci.a...6af3010?hl=en& The same pseudo-authority that sanctions constellational astrology and its 'predictive' nature are the same numbskulls who publically made idiots of themselves last year in regard to planetary 'definition'.You simply could not make up this comedy if you tried and the way they are now stuck between a meaningless wordplay and the physical structure and motion of objects around the Sun. Clear skies, Greg -- Greg Crinklaw Astronomical Software Developer Cloudcroft, New Mexico, USA (33N, 106W, 2700m) SkyTools: http://www.skyhound.com/cs.html Observing:http://www.skyhound.com/sh/skyhound.html Comets: http://www.skyhound.com/sh/comets.html To reply take out your eye |
#43
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Pluto is a planet again..
Greg wrote:
You know, Chris, we've had this discussion what? four times now? every time you trot out these half-baked ideas and I patiently explain that there is a real problem that can't simply be ignored and how that problem is nicely solved by the new definition. Chris wrote: No doubt we'll have it again (although I'd never stoop to calling your opinion "half-baked"). You can explain it all you want- I simply don't see that there ever was a problem (although I think there is now). Greg wrote: Ah, ok, I see now. Why didn't you just come out and say from the start that you were among those disgruntled who cling to "Pluto is a planet?" Chris wrote: No, I'm just recognizing that it and many other objects are planets. Chris: Would you just shut up and quit with your disgruntled, half baked ideas! Greg has spoken. Greg: You look childish (and your arguments futile) when you start "trotting" ad hominem attacks; especially towards people like Chris, who are among the brightest of those who post here. You don't have a monopoly on what ideas make up the argument for a planet. Errol |
#44
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Pluto is a planet again..
"Paul Schlyter" wrote in message ... In article , Chris L Peterson wrote: IMO the decision to rigorously define "planet" was a solution looking for a problem (and in fact, created its own problems). The IAU definition of "planet" wasn't that rigorous really. First, it doesn't specify how large a deviation from the hydrostatic equilibirion shape is allowed for a body to still be considered a "planet". Some deviation is obviously allowed, or else the mountain ranges of the Earth would disqualify the Earth from being a planet. Second, the phrase "cleared its neighbourhood" is a quite fuzzy phrase, open for interpretation. And both of these effects are a result of mass. Initially it made no sense to me why they didn't just define a planet as a body of mass "P". Arbitrary? Yes. Fuzzy? No. It seems they could have used their existing definition to do the calculations to initially define "P", then fine tune it over time. The problem is that to define "P", they would have to define "spherical" and "neighborhood". I don't know, maybe fuzziness isn't so bad. It seems crazy that you could have one body with mass "P" being a planet and another body with mass "P - 10^3 kg" not being a planet. Richard |
#45
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Pluto is a planet again..
"Richard Jarnagin" wrote in message
link.net... And both of these effects are a result of mass. Initially it made no sense to me why they didn't just define a planet as a body of mass "P". Arbitrary? Yes. Fuzzy? No. It seems they could have used their existing definition to do the calculations to initially define "P", then fine tune it over time. The problem is that to define "P", they would have to define "spherical" and "neighborhood". I don't know, maybe fuzziness isn't so bad. It seems crazy that you could have one body with mass "P" being a planet and another body with mass "P - 10^3 kg" not being a planet. Richard Obviously I'm just speaking of the lower limit here. RJ |
#46
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Pluto is a planet again..
"Chris L Peterson" wrote in message ... On Fri, 09 Mar 2007 13:54:52 -0700, Greg Crinklaw wrote: snip I'd call them both planets. I'd distinguish between them by subclassifications. In practice, that's how it's done anyway. The formal definition of "planet" hasn't changed a thing, except for adding a bit of confusion. snip And the difference between a major planet and a minor planet would be? Richard |
#47
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Pluto is a planet again..
On Sat, 10 Mar 2007 17:28:57 GMT, "Richard Jarnagin"
wrote: And the difference between a major planet and a minor planet would be? I'm not sure that's a very useful classification given that planets vary widely and continuously in size/mass. Perhaps this would be a good term to distinguish between bodies that have enough mass to collapse to spheres, and those that don't? Of course, there will be occasional objects that are on the edge, and could be placed in either category. I think the idea of major or minor planets falls into that area Brian introduced: classes designed for presenting ideas to the lay public. I don't see much scientific value. Scientifically useful classifications are more likely to be based on composition, location, or formation history than on size or mass (or whether they happen to have cleared their orbit of other material, which is truly a useless consideration). _________________________________________________ Chris L Peterson Cloudbait Observatory http://www.cloudbait.com |
#48
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Pluto is a planet again..
"Chris L Peterson" wrote in message ... On Sat, 10 Mar 2007 17:28:57 GMT, "Richard Jarnagin" wrote: And the difference between a major planet and a minor planet would be? I'm not sure that's a very useful classification given that planets vary widely and continuously in size/mass. Perhaps this would be a good term to distinguish between bodies that have enough mass to collapse to spheres, and those that don't? Of course, there will be occasional objects that are on the edge, and could be placed in either category. I think the idea of major or minor planets falls into that area Brian introduced: classes designed for presenting ideas to the lay public. I don't see much scientific value. Scientifically useful classifications are more likely to be based on composition, location, or formation history than on size or mass (or whether they happen to have cleared their orbit of other material, which is truly a useless consideration). Agreed. The point that I was trying to make is that when defining subcategories, you are really just regressing one step from defining planets. There will still be fuzziness at some of the boundaries. Richard |
#49
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Pluto is a planet again..
On Sat, 10 Mar 2007 18:42:34 GMT, "Richard Jarnagin"
wrote: Agreed. The point that I was trying to make is that when defining subcategories, you are really just regressing one step from defining planets. There will still be fuzziness at some of the boundaries. I don't think that's universally true. There are categories where there is probably never going to be any fuzziness (terrestrial versus gas giant, terrestrial versus KBO, etc). This is true outside of astronomy as well. Some classifications are very clearly suggested by natural divisions, others are more arbitrary points along continua. It isn't clear to me that the top level classification ("planet", although I'd prefer a different term) needs to be fuzzy at its boundaries- although there's no guarantee that we won't eventually stumble across something that is hard to place. _________________________________________________ Chris L Peterson Cloudbait Observatory http://www.cloudbait.com |
#50
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Pluto is a planet again..
"Chris L Peterson" wrote in message
... On Sat, 10 Mar 2007 18:42:34 GMT, "Richard Jarnagin" wrote: Agreed. The point that I was trying to make is that when defining subcategories, you are really just regressing one step from defining planets. There will still be fuzziness at some of the boundaries. I don't think that's universally true. There are categories where there is probably never going to be any fuzziness (terrestrial versus gas giant, terrestrial versus KBO, etc). This is true outside of astronomy as well. Some classifications are very clearly suggested by natural divisions, others are more arbitrary points along continua. It isn't clear to me that the top level classification ("planet", although I'd prefer a different term) needs to be fuzzy at its boundaries- although there's no guarantee that we won't eventually stumble across something that is hard to place. Obviously it's not universally true. That's why I said "some" of the boundaries. As for it not being clear to you the definition of a planet needs to be fuzzy at its boundaries, it seems to me that depends on what one chooses as a definiton. We could choose a lower and upper mass (or size) limit and have no fuzziness at all. Or we could have something like the IAU definition and have considerable fuzziness. Or we could come up with something in between and have an intermediate amount of fuzziness. But to eliminate fuzziness completely, it appears one has to introduce arbitrariness into the definition. Richard |
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