Pluto reclassified as a planet.

[skepticalbip]

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!

Nah, just a couple hundred objects.

Asteroids with satellites

But then we don't yet know much about the Kuiper belt and even less about the Oort cloud. We may be talking about thousands or even millions of bodies with their own satellites

 

[Malintent]

Is there an argument in there somewhere, either for why the reasons for the demotion were scientific or for why all those other dwarf planets would also have to be considered planets? Or were you merely attempting proof-by-condescension? Are you under the impression that a vote of an astronomers' committee is any more capable of making a labeling convention scientifically correct than a vote of a bishops' committee is of making the doctrine of the Trinity theologically correct?

Pluto got reclassified because we found a whole bunch of other things beyond the orbit of Pluto. Heck, some of them are even bigger than Pluto. When Pluto was the only dwarf planet we knew about, it made sense to classify it as a planet, but now that we know about all those other dwarf planets, it makes more sense to put Pluto in that other category with the others.

And no doubt a committee of physicists had reasons just as persuasive to themselves for why it makes more sense to put a 0.9 mm wave in the "infrared" category with a 0.001 mm wave than in the "microwave" category with a 1.1 mm wave. That doesn't make the categories science. Astronomical taxonomy is still done the way all other taxonomy was done for most of recorded history: people make up labels for categories they feel make sense and make up definitions that ignore distinctions they choose to treat as unimportant. But a couple hundred years ago biologists started moving away from this procedure and started working out how to do taxonomy scientifically; by now they've gotten pretty good at it. Their success has given other sciences biology-envy -- the delusion that they can do categorization scientifically too.

What is interesting is that the behavior of objects in the solar system change behavior depending on how they are described by scietists.

^^^^^ This. ^^^^^

anything that needs to make sense must be consistent (something creationists are not very good at, generally). So, the consistency here is calling the 1 thing that behaves like 100,000 other things the same as the larger group of things, rather than renaming the larger gorup of things that which the smaller group of things are called. It is just plain rational (again, a point of difficulty for the rationally illiterate anti-science creotard).

 

[Bomb#20]

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!

Nah, just a couple hundred objects.

Asteroids with satellites

Also, the asteroids Ceres and Vesta have differentiated layers. But yes, it would be a piece of cake to come up with a reasonable definition that matches common usage. For instance, anything that orbits a star, isn't a star, is roughly spherical, and has a diameter over 1000 miles. That makes Eris the tenth planet. Boo-friggin-hoo. We've already been discovering further-out planets about once a century; what's so bad about continuing the pattern?

 

[Bomb#20]

So, the consistency here is calling the 1 thing that behaves like 100,000 other things the same as the larger group of things, rather than renaming the larger gorup of things that which the smaller group of things are called.

Quantify "behaves like". Does Mars behave more like Ceres or more like Saturn?

No two celestial bodies behave exactly the same. For all X, Y and Z, X behaves more like Y than like Z in some ways and more like Z than like Y in other ways. When we name X the same as Y and differently from Z on the grounds that X behaves like Y, what we're actually doing is deciding we care more about the ways X behaves more like Y than we care about the ways X behaves more like Z.

 

[Shadowy Man]

Also, the asteroids Ceres and Vesta have differentiated layers. But yes, it would be a piece of cake to come up with a reasonable definition that matches common usage. For instance, anything that orbits a star, isn't a star, is roughly spherical, and has a diameter over 1000 miles. That makes Eris the tenth planet. Boo-friggin-hoo. We've already been discovering further-out planets about once a century; what's so bad about continuing the pattern?

Why 1000 miles? That's an arbitrary number.

 

[Emily Lake]

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!

Nah, just a couple hundred objects.

Asteroids with satellites

Darn. Do all of the historical planets have layered compositions? If I recall, mercury doesn't have an atmosphere, but I believe it has a materially different core. Do any of the objects in the asteroid belt or the Kuiper belt have cores or atmospheres?

ETA: I see that Ceres and Eris do have layers.

- - - Updated - - -

Also, the asteroids Ceres and Vesta have differentiated layers. But yes, it would be a piece of cake to come up with a reasonable definition that matches common usage. For instance, anything that orbits a star, isn't a star, is roughly spherical, and has a diameter over 1000 miles. That makes Eris the tenth planet. Boo-friggin-hoo. We've already been discovering further-out planets about once a century; what's so bad about continuing the pattern?

Why 1000 miles? That's an arbitrary number.

All classifications have an element of arbitrary division to them.

 

[Shadowy Man]

All classifications have an element of arbitrary division to them.

I disagree with this statement. Or at least, I would say that you can't make this statement categorically.

In particular, as it applies to the current discussion about the definition of "planet", one can look at Steven Soter's approach to planet classification. It presented natural divisions of planetary characteristics that made a clear distinction between the eight major planets and the dwarf planets (including Pluto). Now, I guess you could claim that the characteristics he chose to use are "arbitrary" but they do have physical basis and may have relevance to planetary formation theories.

 

[skepticalbip]

Darn. Do all of the historical planets have layered compositions? If I recall, mercury doesn't have an atmosphere, but I believe it has a materially different core. Do any of the objects in the asteroid belt or the Kuiper belt have cores or atmospheres?

Comets come from the Kuiper belt or Oort cloud. When they are close enough to the sun for their surface ices to sublime they have atmospheres. Their cousins are still out there waiting for a gravitational bump to send them in but they may have extremely tenuous atmospheres. Whether you would classify them as layered or not I dunno. They are composed of rocky material and ices.

You have apparently already dropped moons as a possible way to classify planets which is just as well. Both Mercury and Venus have no moons but poor little demoted Pluto has five moons that we are aware of.

 

[Bomb#20]

But yes, it would be a piece of cake to come up with a reasonable definition that matches common usage. For instance, anything that orbits a star, isn't a star, is roughly spherical, and has a diameter over 1000 miles.

Why 1000 miles? That's an arbitrary number.

"That's not a bug; it's a feature." And it gets better. Not only is 1000 an arbitrary number, but mile is an arbitrary unit from the English unit system, and England is an arbitrary country. Adopting this definition would be truth in advertising: a frank and long-overdue admission that the world of inanimate objects is a continuum, astronomical classifications are an exercise in drawing lines upon it, and the distinction between asteroids and planets is no more "out there waiting to be discovered" than the distinction between planets and brown dwarf stars. "Cutting nature at its joints" is for biologists.

But why 1000 miles? That's because, of all the arbitrary numbers of all the arbitrary units from all the arbitrary countries on an arbitrary planet that we could pick, that one is perfect. (And therefore, in some twisted sense, not arbitrary. ) There was a wonderful period piece a while back called "The Englishman Who Went Up a Hill But Came Down a Mountain"; it's an exact metaphor for the Pluto debate. It's a loosely fact-based movie about a Welsh community that was proud of its mountain and not altogether thrilled about the English surveyors there to measure it and determine if it was really a mountain or merely a hill, based on whether it was over 1000 feet high.

(Of course, if the IAU ever does decide to restore traditional terminology by drawing an arbitrary line just below Pluto, they will inevitably decide it's more scientific to draw the line at a radius of 1000 kilometers, thereby lousing up the lesson in what is and isn't science.)

 

[Shadowy Man]

If you're not interested in actually discussing the issue at hand, there are easier ways to say it.

There are ways of classifying Solar System objects using non-arbitrary divisions. And some of them might actually be useful.

 

[Malintent]

Why 1000 miles? That's an arbitrary number.

"That's not a bug; it's a feature." And it gets better. Not only is 1000 an arbitrary number, but mile is an arbitrary unit from the English unit system, and England is an arbitrary country. Adopting this definition would be truth in advertising: a frank and long-overdue admission that the world of inanimate objects is a continuum, astronomical classifications are an exercise in drawing lines upon it, and the distinction between asteroids and planets is no more "out there waiting to be discovered" than the distinction between planets and brown dwarf stars. "Cutting nature at its joints" is for biologists.

But why 1000 miles? That's because, of all the arbitrary numbers of all the arbitrary units from all the arbitrary countries on an arbitrary planet that we could pick, that one is perfect. (And therefore, in some twisted sense, not arbitrary. ) There was a wonderful period piece a while back called "The Englishman Who Went Up a Hill But Came Down a Mountain"; it's an exact metaphor for the Pluto debate. It's a loosely fact-based movie about a Welsh community that was proud of its mountain and not altogether thrilled about the English surveyors there to measure it and determine if it was really a mountain or merely a hill, based on whether it was over 1000 feet high.

(Of course, if the IAU ever does decide to restore traditional terminology by drawing an arbitrary line just below Pluto, they will inevitably decide it's more scientific to draw the line at a radius of 1000 kilometers, thereby lousing up the lesson in what is and isn't science.)

These symbols you are using to communicate are arbritrary... therefore you make no sense.

 

[Emily Lake]

All classifications have an element of arbitrary division to them.

I disagree with this statement. Or at least, I would say that you can't make this statement categorically.

In particular, as it applies to the current discussion about the definition of "planet", one can look at Steven Soter's approach to planet classification. It presented natural divisions of planetary characteristics that made a clear distinction between the eight major planets and the dwarf planets (including Pluto). Now, I guess you could claim that the characteristics he chose to use are "arbitrary" but they do have physical basis and may have relevance to planetary formation theories.

I would argue that the "natural" classification are arbitrary groupings themselves. He simply picks and chooses where to draw lines of similarity and difference. Pretty much all human classification systems contain an aspect of arbitrariness. We decide "this thing make these similar". We refine it over time, and we build around it, but classifications are at heart about how to group things on perceived similarity and difference.

- - - Updated - - -

Comets come from the Kuiper belt or Oort cloud. When they are close enough to the sun for their surface ices to sublime they have atmospheres. Their cousins are still out there waiting for a gravitational bump to send them in but they may have extremely tenuous atmospheres. Whether you would classify them as layered or not I dunno. They are composed of rocky material and ices.

You have apparently already dropped moons as a possible way to classify planets which is just as well. Both Mercury and Venus have no moons but poor little demoted Pluto has five moons that we are aware of.

I'm making it up as I go along. I have no particularly good reason to either include or exclude moons, other than a very naive attempt to come up with a "rational" classification that still includes Pluto as a planet!

 

[Emily Lake]

There are ways of classifying Solar System objects using non-arbitrary divisions. And some of them might actually be useful.

Perhaps I'm simply ignorant, but I don't see how that's possible. Useful yes; completely non-arbitrary no.

 

[skepticalbip]

Comets come from the Kuiper belt or Oort cloud. When they are close enough to the sun for their surface ices to sublime they have atmospheres. Their cousins are still out there waiting for a gravitational bump to send them in but they may have extremely tenuous atmospheres. Whether you would classify them as layered or not I dunno. They are composed of rocky material and ices.

You have apparently already dropped moons as a possible way to classify planets which is just as well. Both Mercury and Venus have no moons but poor little demoted Pluto has five moons that we are aware of.

I'm making it up as I go along. I have no particularly good reason to either include or exclude moons, other than a very naive attempt to come up with a "rational" classification that still includes Pluto as a planet!

I think maybe a grass roots movement demanding poor little Pluto's reinstatement may be the only way. Convince all alumni to all universities to stop donating and all Congress critters to stop funding all universities until all the astronomers in their university agree to reinstate Pluto. Maybe allow them to keep their current definition of planet but include a rider which would grandfather poor Pluto back into the fold.

We need to start the movement. I haven't written my Congress critter for a while. He may be looking for a popular cause to back in order to attract more popular vote for his next campaign.

 

[Shadowy Man]

There are ways of classifying Solar System objects using non-arbitrary divisions. And some of them might actually be useful.

Perhaps I'm simply ignorant, but I don't see how that's possible. Useful yes; completely non-arbitrary no.

Well, based on your earlier post, it is not clear that you and I are agreeing on the definition of the word "arbitrary". So, unless we put in the effort to clarify our terms, it is probably not useful to continue to argue this point.

For example, one might say that using eighteen as the age of distinction between a child and an adult is arbitrary. But the distinction between the unborn and the born child is very much less arbitrary, despite the difference of the actual child being so minor. Classifying people as either male or female is not arbitrary, even though there are a few cases here and there that are not as easily classifiable.

Anyway...I have posted many times, and I still believe, that a classification system should add value. It shouldn't be a popularity contest.

 

[James Brown]

Nah, just a couple hundred objects.

Asteroids with satellites

Also, the asteroids Ceres and Vesta have differentiated layers. But yes, it would be a piece of cake to come up with a reasonable definition that matches common usage. For instance, anything that orbits a star, isn't a star, is roughly spherical, and has a diameter over 1000 miles. That makes Eris the tenth planet. Boo-friggin-hoo. We've already been discovering further-out planets about once a century; what's so bad about continuing the pattern?

Well, the official number of planets has dropped in times past as well. At one point the number was as high as 15. So we could say that there shouldn't be any problem with continuing the pattern from nine to eight.

 

[Shadowy Man]

Well, the official number of planets has dropped in times past as well. At one point the number was as high as 15. So we could say that there shouldn't be any problem with continuing the pattern from nine to eight.

At what point was the *official* number of planets 15?

 

[Emily Lake]

Perhaps I'm simply ignorant, but I don't see how that's possible. Useful yes; completely non-arbitrary no.

Well, based on your earlier post, it is not clear that you and I are agreeing on the definition of the word "arbitrary". So, unless we put in the effort to clarify our terms, it is probably not useful to continue to argue this point.

For example, one might say that using eighteen as the age of distinction between a child and an adult is arbitrary. But the distinction between the unborn and the born child is very much less arbitrary, despite the difference of the actual child being so minor. Classifying people as either male or female is not arbitrary, even though there are a few cases here and there that are not as easily classifiable.

Anyway...I have posted many times, and I still believe, that a classification system should add value. It shouldn't be a popularity contest.

Hmm. I don't know that we disagree on what constitutes "arbitrary" so much as we disagree on what constitutes a "classification system". A classification system takes things that exist along a spectrum or distribution, and imposes groupings on them to allow for manipulation and comparison. The definitions of colors, for example, are classifications. Classification of music into genres is similar.

I agree that the classification system should add value - that's the whole point of having a system. It should allow for comparison and manipulation of information in a meaningful way.

In the case of planets versus other bodies... it's entirely arbitrary. There are certainly hundreds of characteristics that could be considered, much as there are so many different ways one might consider classifying plants and animals. There's an arbitrary choice being made about which characteristics the scientists think make the most sense for making a group of things called "planets". Just as biologists arbitrarily decided that spinal cords were one of the most important characteristics to start making a classification system for animals, so we get the phylum chordata. It was a place to start making groups - ti was something that they had in common, and that allowed scientists to easily distinguish between one set and another. But the selection of spinal cords as the distinguisher was itself arbitrary in the classification system.

I don't think that born versus unborn and male versus female are classifications. It's not a grouping intended to allow for comparison. It's a description of state. It would be like saying that monkey versus teapot isn't arbitrary. Of course it isn't. But that's also not a classification.

I fear I'm being clear as mud on this. I perceive a relationship, but I'm at a loss as to how to express it.

 

[bilby]

There are nine planets. My textbook says it. I believe it. That settles it.

 

[Shadowy Man]

In the case of planets versus other bodies... it's entirely arbitrary. There are certainly hundreds of characteristics that could be considered, much as there are so many different ways one might consider classifying plants and animals. There's an arbitrary choice being made about which characteristics the scientists think make the most sense for making a group of things called "planets".

I think this is the heart of it. I see your point now. One could envision defining planet as those objects with atmospheres, and then you'd get a different result. The question is whether the choice of mass/roundness and orbital parameters as defining characteristics of a "planet" is arbitrary. I agree that you could view it that way. However, once you do decide on these characteristics there are non-arbitrary ways of classifying them. But I see your point and concede that I was incorrect to assert that completely non-arbitrary methods could be use to classify Solar System objects.