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Posted by: Kevin Heider Oct 15 2006, 01:45 AM

I had assumed that 1 Ceres was still considered an Asteroid since it orbits in the asteroid belt and has the same origin as the other asteroids.

But I noticed that on http://en.wikipedia.org/wiki/1_Ceres they say: "Ceres is a 'dwarf planet', and may no longer be classified as an asteroid."

Wikipedia cites the IAU website at http://www.iau2006.org/mirror/www.iau.org/iau0603/iau0603_Q_A2.html that states:
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Q: What is Ceres?

A: Ceres is (or now we can say it was) the largest asteroid, about 1000 km across, orbiting in the asteroid belt between Mars and Jupiter. Ceres now qualifies as a dwarf planet because it is now known to be large enough (massive enough) to have self-gravity pulling itself into a nearly round shape. [Published reference for shape of Ceres: P. Thomas et al. (2005), Nature 437, 224-227. Dr. Peter Thomas is at Cornell University.] Ceres orbits within the asteroid belt and is an example of a case of an object that does not orbit in a clear path. There are many other asteroids that can cross the orbital path of Ceres.

Q: Didn’t Ceres used to be called an asteroid or minor planet?

A: Historically, Ceres was called a “planet” when it was first discovered (in 1801) orbiting in what is known as the asteroid belt between Mars and Jupiter. Because 19 th century astronomers could not resolve the size and shape of Ceres, and because numerous other bodies were discovered in the same region, Ceres lost its planetary status. For more than a century, Ceres has been referred to as an asteroid or minor planet.
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Is Ceres still classified as an asteroid since it is located in the asteroid belt? Pluto is a Kuiper Belt Object (KBO) even though it is also a 'dwarf planet'.

Has Pallas become the 1st asteroid discovered? Has Vesta become the largest asteroid (at least until the IAU decides that since Vesta is a damaged, differentiated protoplanet that it was probably spherical in the past)? *IF* Ceres is truely no longer an asteroid, because it is spherical, then those two very basic questions have new answers!

How do we contact the IAU for an official statement on the classification of Ceres as an asteroid?

-- Kevin Heider

Posted by: djellison Oct 15 2006, 09:23 AM

Don't ask the IAU - they don't have a clue what they're doing

Under their rules, Pluto is a Dwarf Planet but no one would deny it's still a Kuiper Belt object. I think it's just a venn-diagram overlap of 'Dwarf Planet' and 'Asteroid' where you'll find Ceres.

Becaus a couple of dozen people held up a particular coloured card in a conference room - suddenly Ceres stops being an asteroid? That's just moronic. It remains a member of the asteroid belt.

That is the pivotal idiocy of all this nonsesne..Pluto is still Pluto and Ceres is still Ceres. One is still a KBO and one is still an Asteroid. If you also decide to classify them as Dwarf Planets or Planets or anything....they're still a KBO and an Asteroid. Whoever decided to try and claim, via Wikipedia, that Ceres is not an asteroid is an idiot.

Doug
(PS - I would be very very wary use Wikipedia as a source of fact or reliable information)

Posted by: edstrick Oct 15 2006, 11:00 AM

The FUNDAMENTAL problem is that the term "Planet" is of pre-scientific origin, and has been adapted on an "everybody knows what a planet is" basis over time as it's use has been "upgraded" during the evolution of of post-telescopic Astronomy.

Definitions tend to split between Descriptive, and Genetic. That's the ultimate schizoid origin of the battle. Io and Titan are planets - - - geologically. But not in genesis. The standard definition evolved to assume planets formed in solar orbit, but moons accreted in planetary orbit... but captured objects?.... should they be defined as moons?... Triton WAS a dwarf planet before it got captured by Neptune....

I consider the whole thing "spectator sport". It's important, but not IMPORTANT... if you get my drift.

Posted by: helvick Oct 15 2006, 12:21 PM

I agree. Time will tell how it works out I suppose and in the mean time we can but watch.

For me I can't see why the term "planet" can't be applied happily to anything that is simply big enough - the hydrostatic/gravitationally spherical thing - provided it isn't actually a stellar or post stellar obect. Then you prefix whatever modifiers that suit the required set:
Classical ("Greek") planets: Everything out to Saturn but excluding earth.
Traditional planets: The "9" including Pluto.
Real or Giant planets: Jupiter, Saturn, Uranus, Neptune (Gotta be BIG to be Real!)
Gas Giant planets: Jupiter, Saturn
Ice Giant planets: Neptune, Uranus
Terrestrial planets: Venus, Earth, Mars, Titan (Rock balls with an atmosphere)
Rock planets: Any planet made primarily of rocks (Mercury, Luna...)
Ice planets: Any planet made of Ice (Pluto, Europa)
Dwarf planets: Pluto, Charon, Eris (The IAU can have this one, OK by me)
Lunar planets: Mercury, Luna, Ceres, Vesta, Charon, Ceres, Eris, Triton,Ariel, Umbriel, Titania, Oberon, Tethys, Dione, Rhea, Iapetus, Io, Europa, Callisto, Ganymede .. (any >1000km and < 5000km diameter body with no significant atmosphere)
Satellite planets: Any planet that is in orbit around another planet.
Minor planets: All the Lunar planets + Dwarf Planets
Red planets: Reddish\Brown ones (like Mars, Io, Titan and Pluto)
Blue planets: Blueish ones (Earth, Uranus, Neptune)
Lonely planets: Ones that are waay out in the void on their own.
Hellfire planets: Hot Jupiters.
etc.

Edited to add:
Apologies to any large round spherical bodies I may have missed - you can have the title:
Forgotten planets.

Clearly I personally don't have an issue with having oodles of planets. As I see it we know for certain now that there are billions of them around other stars so adding as many to our own system seems only fair to me.

Share and enjoy!

Posted by: angel1801 Oct 15 2006, 02:17 PM

I would assume (unless the IAU says otherwise) that Ceres is both an asteroid and a dwarf planet at the same time. Of course, the IAU may say some something about this in 2009 at their next General Assembly.

Posted by: alan Oct 15 2006, 02:46 PM

No, if you can't use the new categories to Ceres only, you need to apply them to the other members of the asteroid as well. In that case the other members are small solar system bodies, asteroids no longer exist.

Actually the legacy categories identify the locations of the objects, I don't see any conflict in continuing to use them.

Posted by: Jyril Oct 15 2006, 02:57 PM

Ceres is still an asteroid. The terms 'asteroid' and 'minor planet' will stay in use.

Note the two "mosts": Ceres is an asteroid, Pluto and Eris are TNOs, but none of them is an SSSB (because all of them fulfill the definition of a dwarf planet).

Posted by: ElkGroveDan Oct 15 2006, 03:02 PM

I was going to make that caution when the Wikipedia issue came up in another thread yesteday. Worse, people with an ax to grind are able to simply change entires at will, and then a battle of semantics erupts.

So if anyone doesn't like the Ceres entry go ahead and change it, but be sure to back up your assertions with facts and citations. The Wiki administrators love cites. If you can provide a cite, to them it becomes truth.

Posted by: Jyril Oct 15 2006, 03:26 PM

Cites make claims verifiable, not truth. You must realize that Wikipedia is an encyclopaedia, not a scientific work. It is a collection of information and is always dependent on other sources which may not be accurate (like the CIA "fact"book). This is true with all encyclopaedias. Often only a real expert can say if a source is credible or not. Wikipedia editing system is especially problematic since even totally clueless users can contribute. It was especially frustrating in the case of Eris (then 2003 UB313) article; people kept (and still keep) adding the cursed X-word into the article despite it was already mentioned there.

Posted by: Mariner9 Oct 15 2006, 07:36 PM

edstrick said it best: 'planet' is a term that predates our current scientific knowledge of solar system objects.

Since 'asteroid' also is from a fairly early time, I think that word falls into the same catagory.

I think any attempt to force a firm scientific definition onto 'planet', 'asteroid' and even 'comet' is ultimately doomed, and counterproductive.

We should just leave those words as the 'common man's vernacular' and let the scientific world come up with terminology that suits the evolving understanding of our cosmos.

If people want to get down to the nitty gritty, what about earth crossing 'asteroids' whose orbits don't even get out to the main belt? What about extinct comets that still remain in their elliptical orbits, but no longer form a coma? And when does something get so small it is no longer an asteroid, but just a meteoroid?

Ugh. Trying to sort it out with non-scientific terminology is just too annoying.

My vote (which doesn't count with the IAU) is to leave Ceres an asteroid, because it is obviously in the asteroid belt.

Posted by: edstrick Oct 16 2006, 10:01 AM

Another term, one I actually hope gets adopted, is ROGUE PLANET, a planetary object in interstellar space (dynamically), unbound to any star (or brown dwarf). The term had a history in fairly early science fiction, and I think was used in the 1950's TV SF series like Rocky Jones, Space Ranger. The Oxford English Dictionary's science fiction terminology project should have the earliest documented -- so far -- occurrence of the phrase.

Posted by: Rob Pinnegar Oct 16 2006, 01:48 PM

It probably will get adopted eventually. Although the dictionary definition of "rogue" doesn't really match the description, "rogue planet" has the advantage of having few syllables.

It is also just unambiguous enough to be workable. My guess is that, if you were to ask the average person on the street what a "rogue planet" is (and told them that they weren't allowed to describe it in terms of alien civilizations on Star Trek), a good-sized percentage would come up with the idea of a planet unbound to a star, probably describing it as "a planet flying uncontrollably through space" or something like that. So it's pretty intuitive.

If anyone in the astronomical community doesn't like it and thinks something else would be more appropriate, they had better start pushing their idea now -- and it'd be a good idea to come up with something less cumbersome than "Small Solar System Bodies" (a good example of nomenclature that is clear, unambiguous, and will likely be used by just about nobody).

Posted by: Stephen Oct 17 2006, 05:38 AM

Hmm. If asteroids no longer exist (because they have all metamorphosed into "dwarf planets" and "small solar system bodies") that raises the question of whether Kuiper Belt Objects (KBOs) have vanished from the astronomical lexicon as well.

And what about comets? Are we now supposed to talk about "Halley's Small Solar System Body"?


It seems they have been abolished. Along with "meteors", "meteoroids", "meteorites", "cosmic dust", etc etc.

======
Stephen

Posted by: Jyril Oct 17 2006, 08:44 AM

Asteroids no longer exists!? What happened to them?

You are mistaken. The Small Solar System Body is an umbrella term which includes all objects other than the Sun, planets and dwarf planets.

The terms 'asteroid' and 'minor planet' will continue in use. The original definition draft would have removed the term 'minor planet'. But since the term has been used 150+ years, it was deemed stupid to scrub it.

Posted by: djellison Oct 17 2006, 09:04 AM

Minor planet would make a lot more sense than 'dwarf' planet - but neither is appropriate for a class of body that hasn't 'cleaned up' it's area. That would be like calling anyone who lives in a block of apartments a dwarf human.

Doug

Posted by: nprev Oct 18 2006, 04:06 AM

Again, this is the age-old battle between the human tendency to put things into neat categories and Nature's inclination to have things exist along a continuum of parameters. Any distinction we make for planets therefore must be essentially arbitrary. For example, what do the terrestrial planets & the gas giants really have in common? Not very much, from casual examination.

Given that, I have to buy off on the "Mercury Standard": if it's smaller than Mercury and/or doesn't orbit the Sun independently, then it ain't a planet. Rationale: Mercury is the smallest body that has been universally accepted as a planet since antiquity.

We have to draw a conceded arbitrary line somewhere, and perhaps since the very term "planet" was derived from some of the oldest recorded astronomical observations in Western culture we should use the smallest member of the Mercury-Jupiter continuum to define the threshold for planethood.

My two-one-hundredths of a (badly inflated) dollar!

Posted by: akuo Oct 18 2006, 08:40 AM

As far as I know, Pluto has been assigned a minor planet number (sorry, not minor planet, "small solar system thingy" or whatever the term was) in http://cfa-www.harvard.edu/iau/special/08747.pdf together with Eris and Dysnomia (Xena & Gabrielle).

This should mean that (1) Ceres is still the number one "minor planet" and still an asteroid. Unless there is a further disjoint within the sets of minor planets and asteroids. Funnily, it looks like dwarf planets are also a subset of minor plan... Small Solar System Objects.

Posted by: Jyril Oct 18 2006, 09:17 AM

Dwarf planets are not SSSBs. That is clear from the definition. And not all minor planets are SSSBs.

Posted by: tuvas Oct 18 2006, 06:39 PM

Name 4 minor planets that aren't SSSBs, I only know of 3.

Posted by: Jyril Oct 18 2006, 07:05 PM

What do you mean? There are only 3 non-SSSB minor planets i.e. dwarf planets for now.

2003 EL61 and 2005 FY9 will be most likely promoted into the dwarf planet status soon. Sedna, Orcus, Quaoar, Varuna, Ixion, and some others will follow.

Posted by: JRehling Oct 18 2006, 10:18 PM

Which is a compelling reason for not trying to enforce a formal definition.

Neptune's quite different from the KBOs. It's easy to imagine needing a term to distinguish the two.

What do Mercury and Neptune on the one hand have in common vs. Ceres on the other hand such that it makes more sense to put Mercury with Neptune than with Ceres? Scientifically, nothing. Historically, just a pinch.

There is no formal definition of "river" as opposed to "stream". There is a formal distinction between baryons and leptons. Without a reason to suppose that "planet" is a category like baryon, people are treating it like one. It's not -- it's like "river".

What we have are two (or more sides) dueling over who can be less wrong by proposing a less-bad formal definition for something that, like "river", doesn't need or deserve one.

The stuckness seems to come from the fact that just thirty years ago, it looked like there might be a significant gulf between planets and asteroids. When the facts have disproven that, the response should not be to focus on Ceres and Pluto, but to question what kind of category "planet" is -- like "river" or like "baryon". And call me gruff, but if someone dodges that question, I think they're dodging taking this issue seriously.

Posted by: nprev Oct 19 2006, 09:04 AM

Couldn't agree more, JR.

It's hard by definition for objective scientific methodology to cope with subjective categories/concepts like "planet", "animal", "plant", etc. that predate modern taxonomical philosophy, and the IAU's obvious agony, indecision, and confusion is a direct result.

IMHO as I previously stated, an arbitrary line must be drawn, and not everybody will like it, but it must be done merely to put the whole mess behind us! It's painful to watch the IAU strain to produce all these sub-planetary sub-categories, and for what?

Posted by: Mariner9 Oct 19 2006, 08:46 PM

As an aside, I've found a useful comeback for the next time one of your friends or colleagues asks "Why can't those darn people define what a 'planet' is? I should think it should be clear by now!"

Just give them a terrestial example, like I did to a friend. "Well, a pebble, a boulder, and a mountain are all basically made out of the same thing... why do they have different words for them?"

If that doesn't stop them in their tracks, keep going with "And by the way, when does a pile of dirt and rock go from being a pile to a mound, and then into a hill? And exactly what is the difference between a hill and a mountain anyway? And don't try to tell me mountains have rocky tops, have you taken a good look in New England lately? And why is there a mountain range called the Blue Hills?"

So far I haven't had to go much past "pebble, boulder and mountain'

Posted by: JRehling Oct 19 2006, 10:05 PM

The US state of Maryland all by itself has numerous named peaks which completely confound the terms, all located within a short distance of each other.

As a couple of the more extreme examples, Conneway Hill is 3193 feet high while Hearthstone Mountain is 2021 feet high. Just in Maryland, there are dozens of "hills" higher than that "mountain" and over a dozen "mountains" shorter than that "hill". You can only imagine what extreme examples could be found if you included the rest of the [English speaking] world.

The big difference here is that there is general agreement that the two terms serve a role and that "mountain" is the higher one, and that for any of the above entities, at least one of the two terms ought to apply. Moreover, there is no pretense of a natural distinction between the two terms. In that way, mountains and hills make a poor analogy, because it did once seem that there was a natural low end of the planet size range. The thing now is to watch how people react to the lack of such a distinction -- something that was always known to be true of hills/mountains.

Posted by: Kevin Heider Oct 20 2006, 03:26 AM

Mercury may have been much more like Neptune and Uranus if Mercury was a http://en.wikipedia.org/wiki/Chthonian_planet Planet. Pluto and Ceres certainly had much more mundane pasts.



This is true. Forty years ago, Mercury was the smallest planet and Ceres was a "mostly ignored" space rock.

-- Kevin Heider

Posted by: JRehling Oct 20 2006, 06:29 AM

Mercury couldn't have been a [pre]Chthonian planet. You would have to put a giant planet much closer to Sol than Mercury is to boil off the hydrogen before the early heavy bombardment began.

The planet category underwent "feature creep" -- the one thing that Mercury and *Jupiter* have in common is that they are easily visible to the naked eye. When Uranus was discovered, size became the criterion: planet then became a category not of astronomical observation but of astronomical reality. (Actually, Earth broke that seal first.) Mercury can't be kicked out of the club because it's a charter member, but that's only if you allow for the historical trappings of the category. But if you stick to visual magnitude as a criterion, then Neptune is kicked out. So Mercury and Neptune have been joined under one term precisely because the "planet" category is a hodgepodge. Since it's a hodgepodge, the effort to formalize it is essentially doomed.

If subsequent discoveries play out just right, Mercury will be on the firing line next. Note that Mercury, which comes within about 0.24 AU of Venus, is presumed to have cleared its orbit. If 0.24 AU is the standard, I think we're going to find plenty of things in or past the KB that don't have anything as large as Venus within 0.24 AU of them. And if I were to bet, some of them will be bigger than Mercury.

Posted by: nprev Oct 23 2006, 12:42 AM

Again, I think that the Mercury Standard is perfectly acceptable precisely because of its historical roots.

Let's face it: We're never, ever gonna have a truly empirical, rigorous definition of "planet", so the term may as well be linked to its colloquial qualities rather then all these nit-picking characteristics proposed by the IAU.

By that standard, we have eight planets...but I too feel that we'll find objects Mercury-sized or better in the coming years, and the whole debate will begin anew...

Hmm...Remember when Pluto was thought to be Earth-sized? If that had been true, we wouldn't have ever had this debate. TNOs would have become TPOs, and no question of their planetary status would ever have been raised. Just goes to show how perceptually-influenced this issue really is.

Posted by: akuo Oct 23 2006, 09:05 AM

"Mercury-standard" is in no way acceptable. That puny rock ball is smaller than some moons.

I recommend the planetary status of Mercury to be removed. For any Mercury fans out there, think of it in this way: you may be losing a planet but you will be gaining a Vulcanoid.

Posted by: nprev Oct 23 2006, 09:19 AM

...and Ganymede, Callisto, Titan and Triton were known to the ancient naked-eye observers that coined the term "planet"?

If they were, then I'd find your argument persuasive. However, the subjectivity of the very concept of a planet seems to preclude considering the large satellites of gas giants (esp. given their miniscule masses with respect to their primaries) as planets ahead of Mercury. Furthermore, Mercury frequently exceeds the brightness of Sirius when observed from the Earth, and no other putative "dwarf planet" can do likewise.

And as long as I'm touting Mercury, we shouldn't forget that it has a large and apparently convective iron-nickel core with a significant planetary magnetic field. This shows some taxonomical affinity with Earth and the gas giants (Venus & Mars being two rather conspicuous omissions).

Posted by: tedstryk Oct 24 2006, 10:32 AM

Mercury is also about as massive as Mars, far more massive than any moon. The planet/moon distinction has to do with what a world orbits, not size. So I think you will just have to deal with what you consider unacceptable.

Posted by: gpurcell Oct 24 2006, 01:50 PM

As far as I am concerned, Pluto is still a planet and the IAU can just sod off!

They went far, far beyond the scope of their authority--to settle scientific nomenclature issues--and tried, unsuccessfully to meddle in a cultural issue.

What is particularly obnoxious is that they had a panel with folks who at least had the qualifications to address the larger issues behind the classification of Pluto...and yet the brown shirts still staged a coup and imposed their point of view in opposition to what the panel convened to advise the IAU suggested. And then hid behind "science" as a justification for their political manuevering.

'Tis a shameful chapter in the history of the IAU.

Posted by: Kevin Heider Oct 24 2006, 05:40 PM

If that makes you happy, congratulations! But that still doesn't restore Pluto's status.


They were the only authority with the power to make such a change and I think they did a good job.

A year from now the public's backlash will have subsided and Alan's unofficial group (get together) will have a difficult time coming up with a good enough reason to justify overruling the IAU. Unsuccessfully trying to overrule the IAU would probably just make an even bigger joke out of professional astronomers.

I think one of the biggest mistakes was trying to make Charon a Planet. They should have been dealing with just Eris, Pluto, and Ceres. They should have left Charon in the same currently unclassified category as Sedna, Orcus, Varuna, Quaoar, 2003 EL61, 2005 FY9, Ixion, Huya, Chaos, Buffy, etc.

Charon submissively co-orbitals with Pluto. They should not have complicated the issues and emotions by trying to define a 'double planet' and thus re-classify something currently considered as a moon. This concept of keeping it simple is the reason that the current ruling only applies to our solar system.

The IAU followed the rules in place and made a democratic vote based on the members present. If members not present were really that concerned about Pluto's status, they should have made sure that they were present to cast their vote.

You can read my 1st feelings in support of the Aug 24th IAU ruling at: http://groups.google.com/group/sci.astro.amateur/msg/cf5f3051d7d69494

I am still glad to see that there is now a class of objects that are between irregular shaped asteroids and the dominant planets.

-- Kevin Heider

Posted by: gpurcell Oct 24 2006, 06:17 PM

Nonsense. Since when does the IAU have the "power" to determine what is in the end a cultural determination?

Posted by: rogelio Oct 24 2006, 06:58 PM

Pluto-bashers: Please note the following cultural-political-scientific consequences/implications of Pluto’s demotion:

How many people know what Eris is? (My guess: 1%) How many know that Eris is bigger than Pluto? How many know that, but for the machinations of a block within the IAU, their children would be learning that Eris is the 10th planet? That those children will vote someday (well, maybe 30% of them will) and might have voted for a candidate who would have supported the first unmannedspaceflight to the 10th planet?

Posted by: djellison Oct 24 2006, 07:09 PM

It's getting personal in here...don't make me get out my administrative boots marked "delete" and "ban"

Doug

Posted by: Kevin Heider Oct 24 2006, 08:39 PM

The IAU does have the authority to decide how *most* professionals should use a term. You are right that it does not require the general public to use that definition. But I suspect in 100 years, when all of us are dead, that Pluto and his 50+ brothers will not be considered as significant as the 8 true planets.


Most people? You mean the general public that watches reality tv? Maybe 1% of them know of an object called 'Xena' that is bigger than Pluto, and resulted in Pluto being demoted. Almost no-one knows what Eris is. Hopefully 99% of the 'reality tv' group can do single digit arithmetic.

If scientists were announcing a new planet evey year the general public would grow bored very quickly. How many people really care if a new galaxy is discovered at the edge of the current known universe?

Eris will be mentioned as the largest 'dwarf planet' in the chapter labeled 'dwarf planets'.

I still think the term Planet should be truly reserved for the large dominant bodies.

-- Kevin Heider

Posted by: JRehling Oct 24 2006, 08:40 PM

On the hierarchy of organizations with power to suppress public sentiment (should they end up in opposition), the IAU ranks pretty low.

Dictionaries also apply definitions to words, and don't have less authority than scientific boards. "Star" still means, among other things, any pointlike light in the sky. Physics owns one definition of "work" and astronomy owns one definition of "star", but they don't own all of them. "Work" is going to continue to have senses that cannot be measured in newtons, "star" is going to continue to have senses that don't require fusion, and "planet" is going to continue to be applied to Pluto.

In most cases, there's some sort of inertia going on to keep committees from owning words. "Star" maintains its any-point-light-in-the-sky meaning for reasons that stem naturally from the phenomenology of vision. Pluto's planetness has and will continue to have a sort of guerrilla support. A certain segment going all the way to the top, professionally, is going to insist on that.

Committees can add to the dictionaries' list of definitions, but they don't have "delete power". Pluto's going to stay a planet... it's just a matter of which definition. If need be, we'll have a definition that includes the moving stars known to the ancients (that's in the dictionaries now); the (possibly mutable) definition of the IAU; and a definition that includes Pluto and probably Eris. If someone figures out a way to get "delete power" over definitions, I'd like to know what it is.

Posted by: Greg Hullender Oct 25 2006, 01:36 AM

Been a while since High School, I gather. :-) Nothing, and I mean NOTHING, is more fun than being able to tell an adult "you're wrong!" (Respectfully, of course.) :-)

--Greg (Class of 1977, so it's been a while for me too actually)

Posted by: JRehling Oct 25 2006, 01:55 AM

I taught high school... and undergraduates. But since when do rebels clamor for maintaining the status quo as it's printed in their books?

Nobody arguing for any of the respective definitions has a higher degree than I do. I'm not any more junior to them than Ben Franklin was to George III.

Well, I'm sure many of them are older than I, but not all.

It's not age nor rank nor slogans that makes anyone right here, though: it's being right. "Planet" isn't any more amenable to or needful of formal definition than "river", and nothing in 2006 changed that. As to how much sway the right answer will end up having, that's always a good question.

Posted by: Stephen Oct 25 2006, 02:11 AM

When I did geography in high school--a discipline, BTW, which has apparently been abolished from school curricula, at least in Australia--the term "mountain" had a formal definition: it was a peak 3000 feet or over. Anything under that was a mere hill.

But that was the geographers' definition. Most other people knew nothing about such technicalities--or if they did (eg the cartographers responsible for drawing the maps with all those "Mount X's" sprinkled across them) they happily ignored them--and had been happily applying the words "mount"and "mountain" (not to mention combinations like "mountain range") to heights well under 3000 feet.

Frankly I intend to apply the same principle to "planet": I shall ignore the edicts of the IAU and continue to use the word "planet" rather than "dwarf planet" for Pluto. IAU members may feel themselves under some kind of obligation to adhere, but AFAIK the IAU does not have copyright or trademark control of the word so that means the rest of us are free to do as we see fit. If the Academie Francaise cannot stop the French public using Franglais I'd like to see the IAU stop English-speakers using the word "planet" for Pluto.

======
Stephen

Posted by: JRehling Oct 25 2006, 02:38 AM

This case has more thorny issues than just the height cutoff. For example, on a plain nearly universally 2990 feet above sea level, is a ten-foot bump a mountain? On a craggy surface that is around 4000' feet high, which points are recognized as independent peaks -- there could potentially be thousands of local maxima or an almost unlimited number if you recognize the fractal surface of the rock. So not only height, but some things like convexity and spatial frequency also have to be formalized. I think the "formal" approach with mountains is to use a well-defined cutoff for height but to be completely you-know-it-when-you-see-it with regards to what is a peak.

There's a joke that ends with, "We've already established what you are; now we're negotiating the price." So we've already agreed that you know a mountain when you see it; now we're trying to limit the degrees of ambiguity from five to four.

Posted by: Greg Hullender Oct 25 2006, 03:14 AM

A point worth mentioning for the benefit of the "planet is a cultural term" crowd: we are talking about only eight objects (no more than 100 max) at the moment. Equating this issue with rivers or mountains, which exist by the thousands, if not tens of thousands, is not credible. Further, the general public has far, far more contact with a variety of mountains and rivers, and the distinction between those and "hill" and "stream" is likewise far more important to the average joe (who might need to cross one), and thus, far more likely to genuinely have a "cultural" component. For "planet" vs. "moon" or "dwarf planet" or whatever, the impact on the average person (as opposed to the specialist) is nothing more significant than winning or losing a point in Trivial Pursuit.

So I'd say, no, you have not proven your case that "planet" is a "cultural term." Planets are squarely in the realm of science. No one else really cares.

--Greg

Posted by: nprev Oct 25 2006, 04:10 AM

Ye gods...gotta tell ya, I'm about ready to call the Jerry Springer Show & just have us all do a free-for-all while the studio audience chants for more!

Well, we're all humans, with human perceptions, opinions, and emotions. Beginning to think that that only truly unambiguous categories of objects in the Universe are hadrons & leptons! (Well, quarks, too, of course...)

Heck, maybe that isn't funny...I might be right!!! The other extreme would be black holes...

Posted by: JRehling Oct 25 2006, 07:57 PM

That's a difference, but why is it a relevant difference? I see no reason why there being fewer of them makes them not "cultural". Stars outnumber (terrestrial) mountains. Galaxies outnumber (terrestrial) rivers. Does that make galaxies more or less cultural than rivers, or is number irrelevant to the matters at hand?

Of course, we could talk about continents, which number roughly the same as planets, and the continent-ness of Europe and the non-continentness of India.



There is no question that geography intrudes on the consciousness of the layfolk more than astronomy.

However, the term "planet" also has a tenuous association with science. And as a preamble, let's not confuse the objects in question with the term. Scientists do science concerning Mars; that does not mean that all of the words used in discussions of Mars are scientific terms, much less that they are all amenable to formal definition.

1) Since Bode's Law has ceased to be serious science, the term "planet" has not held for scientists any significant distinction vs. the bodies just smaller than planets. This isn't like "fungus" and "plant" or "baryon" and "lepton" or "DNA" and "RNA". No natural distinction has been meant, needed, or detected. Unlike the other examples I presented in the previous sentence, it is unimaginable that the revelation that something once thought to be a planet and then discovered to be just barely too small (or vice versa) would have any consequence for one's understanding of that object's place in the natural world. In this way, the distinction is quite like that between "river" and "stream".

And by any standards, the comparison between the Mercury-Jupiter similarity and the Mercury-Ceres suggests a category boundary drawn for historic, not scientific, reasons. M::C is more similar in size, composition, structure, etc., than M::J. Originally, Mercury and Jupiter shared naked-eye visibilty and motion and nothing else.

The term "planet" is USED by scientists, but it is not a scientific term any more than "Star Wars" is a scientific movie.

2) Even so, if the term belongs to anyone, it would be the middlebrow "users" that talk about it the most: museums, PBS specials, grade schools, cinematic fiction about spacefarers, and casual readers of newspapers.

There are about 10,000 IAU members. There are, in the developed world, no less than a billion non-astronomers. I would fearlessly posit that the term "planet" is cumulatively used far more often by the billion than the ten thousand: they only need to mention it 1/100,000th as often to do so. If a layperson hears the term once a year, then the average astronomer would need to hear it every 3 waking minutes to make up the gap. Even before acknowledging that many astronomers concentrate on larger things than planets, this seems exceedingly unlikely.



Quite the opposite. The Google query "Pluto is still a planet" garners considerably more hits than the IAU has members. People with no college education have brought the subject of Pluto up with me. Newsweek had a cover story about it. There is far more cumulative eyeball-time coming from laypersons than professionals.

If we were talking about neutron stars or Oberon, the opposite might be true, but with Pluto, it's no contest.

The real measure here is how often do we have scientists using the term with scientific significance, on the one hand, vs. scientists using the term in a vague and offhand way PLUS laypersons using the term in a vague and offhand way. There's really no comparison. Since the asteroids and Pluto were used as data regarding Bode's Law, the term has not had a scientific role. For what it's worth, Icarus no longer accepts submissions on the topic of Bode's Law.

Posted by: gpurcell Oct 25 2006, 08:31 PM

The real issue I see here is a fundamental misuse of science.

The question "What is a planet?" is not a scientific question! There is no Platonic "planetness" out there which can serve as a referent. Any "tests for planetness" are simply an application of more-or-less arbitrary boundary conditions.

What bothers me so much about this is that we see scientists, who for various reasons believe something, employ an argument from authority as opposed to a scientific inquiry on the subject. Of course, they have to do this--a scientific inquiry into the meaningness of the word "planet" would quickly descend into philosophy.

Anytime, anytime I see argument from authority it makes me question the agenda and motives of those making the spurious call. It is particularly obnoxious in science because the whole point of the enterprise is that truth claims can be tested without reference to the individual making the claim.

If an astrobiologist claims that certain tests prove life on Ganymede, the testing procedure can be examined and duplicated. Independent inquiry will settle the truth value of the claim.

THERE IS NO TRUTH VALUE TO THE IAU'S POSITION. IT CANNOT BE TESTED. It is SIMPLY a statement of opinion...and the underhanded and devious manner with which it was arrived at suggests, strongly, that the motives behind those pushing the demotion of Pluto are not good.

Posted by: JRehling Oct 26 2006, 02:00 AM

This aspect of it, quite apart from any specific worlds we are talking about, bothers me a great deal and I think loses scientists a lot of "capital" in terms of winning the masses over to a greater interest in science.

A particularly annoying (though brief) moment in my own education that I recall: An English teacher was talking about a mirror (which I imagine was mentioned in a story; that, I don't recall) and asked the class: "What does a mirror do?" He got several answers: "They reflect light." (Teacher shakes his head 'no'.) "They create an image of something else." (Teacher shakes his head 'no'.) "They create a reverse image of something else." (Teacher shakes his head 'no'.) After everyone with gumption had given up, the teacher let a silence hang in the air for a while. Then he said, "Nothing. A mirror does nothing."

Well, he was free to go ahead and make whatever point he was making, but overall, that minute of classtime was an exercise in jackassery on his part. The real upshot was that no matter how valid an answer was, he was going to shake his head 'no' and stymie everyone before giving his answer, which wasn't any better than anyone else's. At worst, his answer was technically wrong. At best, it was one of several valid answers. But given the moment and his magisterial status (and his generally antisocial personality), he was determined to shoot everyone else down.

The greatest disservice that teacher did was to teachers who actually had a REASON for saying some answers were right and some wrong.

And that's what we have with the 2006 IAU definition. The public is being told that scientists know best (which in many cases they do) when this is really an aesthetic matter and at BEST is an arbitrary selection being introduced for the purpose of adopting some standard, any standard. At worst, it's an arbitrary selection being introduced out of a slavish adherence to aristotelian categories that are vertically hierarchical while mutually exclusive within the same level of the tree -- an assumption that everyone knows does not work well in many cases.

This spends goodwill capital that burns up a little of the eagerness the public might have for enjoying this interesting subject matter, all for the no-gain adoption of a formal definition for which it is inconceivable that science will profit. (Can we imagine riddles of the formation of the asteroids that were once hard to understand but are now laid bare by clarity regarding Ceres's category? Not possibly.) Lose-lose. This would all be true even if Pluto had never existed.