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Pluto reclassified as a planet.

Bomb#20 said:
But that impression comes from familiarity with recent changes. Quite a few correct taxonomic changes were made by creationists in the century before Darwin. Heck, Linnaeus himself identified the mammal category, the primate category, and a number of unobvious insect categories that are still accepted. (And he did start thinking evolutionary thoughts towards the end of his life; but improving taxonomy came earlier.)
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If you're saying that the current IAU classifications are in the same sort of "pre-unifying theory" state as pre-Darwin biology, I'd *partially* agree. Our theories of solar-system formation are getting fairly good (IMO), and that provides us some non-arbitrary basis for classifications.

Bomb#20 said:
Wild guess: botany? Yes, stay the heck out of that fight.
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Actually, a mosquito. In fact, the most important malaria vector in West Africa.
I know very little about plants... Though I do find myself saying "at least we aren't botanists" with relief sometimes;)

Bomb#20 said:
Sorry, I guess that wasn't clear. I meant the category itself being falsifiable, not the membership of a given item in it. There's a very long list of biological categories formerly accepted that have been discarded for making poor predictions. Nowadays we have an explanation for why they performed poorly -- they were polyphyletic -- but we didn't need an explanation to be busily discarding them before Darwin.
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I'd agree that there are quite a few astromomical classifications which should just be scrapped as technical terms. "Planet" may well be one of those terms which should just not have a specific scientific meaning. Hell, including both the rocky planets and the gas giants in a category that excludes asteroids seems pretty silly.

Bomb#20 said:
But Eris isn't a Kuiper Belt Object; it's a Scattered Disk Object. Likewise, what we learn about Pluto would likely apply to Centaurs like Chariklo. The predictive power comes from the objects being nearby on a continuum of properties, not from being fellow members of a yes-no natural category. "Kuiper Belt Object" is a category like "microwave" that comes from drawing arbitrary lines through a continuum.
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Eris and Pluto aren't Kuiper Belt Objects? I was pretty sure they were. I'm really not that up on the classifcations I suppose.

The KBO classification (at least as I understand it) is somewhat similar to microwave, it is true. However, it isn't as arbitrary as you think because there isn't perfect continuity. There exact borders of the regions are fuzzy, but the regions do have different properties. Because of the nature of solar-system formation, the 'spetrum' of objects by distance is a lot less continuous than the EM spectrum.
 
travc said:
Actually, a mosquito. In fact, the most important malaria vector in West Africa.
I know very little about plants... Though I do find myself saying "at least we aren't botanists" with relief sometimes;)
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Damn straight.

Hell, including both the rocky planets and the gas giants in a category that excludes asteroids seems pretty silly.
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Right? Earth is a lot more like Ceres than like Neptune.

Eris and Pluto aren't Kuiper Belt Objects? I was pretty sure they were. I'm really not that up on the classifcations I suppose.
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Pluto is; Eris isn't. It's 96 AU away; the Kuiper Belt only runs from 30 AU out to 50 or 55 AU.

The KBO classification (at least as I understand it) is somewhat similar to microwave, it is true. However, it isn't as arbitrary as you think because there isn't perfect continuity. There exact borders of the regions are fuzzy, but the regions do have different properties. Because of the nature of solar-system formation, the 'spetrum' of objects by distance is a lot less continuous than the EM spectrum.
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True. The structure of the outer solar system is largely governed by resonances -- small integer ratios between orbit periods. The Kuiper belt includes bodies with several resonant periods, up to 2.0 or 2.5 times Neptune's period. Pluto's is 1.5. Eris's is more than three times as long as Neptune's; it's not known if it's in a resonant relation.
 
Bomb#20 said:
Pluto is; Eris isn't. It's 96 AU away; the Kuiper Belt only runs from 30 AU out to 50 or 55 AU.


True. The structure of the outer solar system is largely governed by resonances -- small integer ratios between orbit periods. The Kuiper belt includes bodies with several resonant periods, up to 2.0 or 2.5 times Neptune's period. Pluto's is 1.5. Eris's is more than three times as long as Neptune's; it's not known if it's in a resonant relation.
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Ah, I did not know that.

Classifying by orbital resonaces makes some sense with respect to formation. Though, I'm guessing that the real reason is that it is a guide to actually finding the objects.

At least people are now thinking about systematics and not just taxonomy. I suspect the astronomical classification system will become more sensible over time.
 
3. Dimitar Sasselov, the director of Harvard’s planetary program, the Origins Of Life Initiative, argued: A planet is the smallest spherical lump of matter that formed around stars or stellar remnants. Pluto IS a planet.
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If true, then so are most of the moons, an asteroid or two, and what I predict will eventually be countless trans-neptunian objects. I suspect that much of the debate centers around so many people thinking, "My grade school teacher said that there are nine planets, so that's all there is to say about it."

I agree that the problem stems from a lack of definition for the word 'planet'. It's curious that other astronomical terms like 'moon', 'star', and 'galaxy' don't elicit this much disagreement.
 
James Brown said:
3. Dimitar Sasselov, the director of Harvard’s planetary program, the Origins Of Life Initiative, argued: A planet is the smallest spherical lump of matter that formed around stars or stellar remnants. Pluto IS a planet.
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If true, then so are most of the moons, an asteroid or two, and what I predict will eventually be countless trans-neptunian objects. I suspect that much of the debate centers around so many people thinking, "My grade school teacher said that there are nine planets, so that's all there is to say about it."

I agree that the problem stems from a lack of definition for the word 'planet'. It's curious that other astronomical terms like 'moon', 'star', and 'galaxy' don't elicit this much disagreement.
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Yeah, the whole reason they demoted Pluto was that it's merely one of many and not even the biggest one in it's orbit. If Pluto is a planet then so are a bunch of other objects.
 
We should not be coming up with a classification scheme based on what we desire to have in each classification. Ideally, the classification scheme adds value to our understanding of the objects being classified. If not, then it's simply a popularity contest. If the word "planet" is merely to mean "what people want to call 'planet'" then go ahead and make Pluto a planet. If we really think that classifying Solar System objects helps us understand them better, then lets come up with a classification scheme that actually does that. Unfortunately, because we still don't really know all the details on how the Solar System was formed, it is non-trivial to do this. Perhaps we should be talking about classifications like: terrestrial objects, jovian objects, cerean objects (asteroid belt), kuiper belt objects (incl. Pluto), and comets. At least that many, and the borders aren't even always clear here. And perhaps we'll see how these categories relate to their formation and evolution. Understanding this will help when we start trying to understand the formation of extrasolar systems.

To simply say that anything that is spherical is a planet isn't helping either. How spherical is spherical? And if you draw the line there at hydrostatic equilibrium, what useful things does that tell you about the objects in question?
 
How about we go back to the original definition - an object visible in the Earth's night sky to the unaided human eye that moves relative to the background of "fixed" stars.

So we have Mercury, Venus, The Sun, The Moon, Mars, Jupiter, Saturn, The ISS, The Iridium Constellation, several dozen other man-made satellites, occasional comets, the odd high-altitude jet, some aurorae, some spent rocket ascent stages, ...

Hmm. Perhaps not.
 
bilby said:
How about we go back to the original definition - an object visible in the Earth's night sky to the unaided human eye that moves relative to the background of "fixed" stars.
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That's not the original definition, so your point is moot.
 
Shadowy Man said:
bilby said:
How about we go back to the original definition - an object visible in the Earth's night sky to the unaided human eye that moves relative to the background of "fixed" stars.
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That's not the original definition, so your point is moot.
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I don't know about moot, but it seems my point was far enough over your head to qualify as a planet ;)
 
Shadowy Man said:
bilby said:
In that case, it cannot be moot, for it has no space in which to moo.

:)
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In space, no one can hear you moo.
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-maurice-the-space-cow-boy-rob-hans.jpg
 
Seems like they could come up with a reasonable definition, without too much difficulty.

A spherical object that orbits the central star(s), and is massive enough to have either:
a) attracted a natural satellite of its own, or
b) formed layers of material compositions of different types

So moons around planets: not planets - they orbit the planet, not the star. If it has any combination of core, crust, and atmosphere, then it's a planet.

I think that retains all of our childhood planets... although I think it might also add a couple. Although maybe not too many, since most of the objects in the asteroid and Kuiper belt don't have distinctly different material cores or atmospheres, and I don't believe that too many of them are massive enough to have their own satellites. Although it's been a very long time since I paid anything more than passing attention to this sort of thing, so I could be opening the door to hundreds of objects that we'd all need to memorize!
 
Emily Lake said:
Seems like they could come up with a reasonable definition, without too much difficulty.

A spherical object that orbits the central star(s), and is massive enough to have either:
a) attracted a natural satellite of its own, or
b) formed layers of material compositions of different types

So moons around planets: not planets - they orbit the planet, not the star. If it has any combination of core, crust, and atmosphere, then it's a planet.

I think that retains all of our childhood planets... although I think it might also add a couple. Although maybe not too many, since most of the objects in the asteroid and Kuiper belt don't have distinctly different material cores or atmospheres, and I don't believe that too many of them are massive enough to have their own satellites. Although it's been a very long time since I paid anything more than passing attention to this sort of thing, so I could be opening the door to hundreds of objects that we'd all need to memorize!
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Nah, just a couple hundred objects.

Asteroids with satellites
 
steve_bnk said:
Funny how rational secular logical people can get so bent out of shape over how an object at the outer edge of the solar system is classified...
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moral, emotional, poetic, awestruck bunch of rationalits... how does that fit into your "christian versus the immoral rest" worldview?

funny? or telling?
 
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