I'm not saying I go into a class and give the 8yr old kids enough info to let them sit an astronomy exam just that I leave them knowing a little - hopefully a lot - more about the universe and excited by it, and wanting to learn more, for themselves, after I've gone.

Slight break from the ordinary...substitute "I Got 9" for "I Got 6" in this classic Schoolhouse Rock video. We could all use some humor & a bit of funk at this point.

My spoon clearly was missing in this soup, so... I shall reveal my un-objective, un-sincere and un-scientific vision here too. (just couldn't stay quiet any longer, just as many of you have felt here)

Well, I am amazed how narrow-minded and concentrating on categories rather than real issues this has been for some parts of it. I mean, like some of you have said earlier, is it really THE thing if one is called planet and the other is something else? The real issue in my mind is the Solar System as a whole, as a complex system (maybe not in Newton's mind), and that in there we have an important place for every rock/comet/planet/kbo/plutino/uranino/mercurino... If the only argue here is "but what about the teachers who now have to figure out a new poem or song or wordplay to teach THE SOLAR SYSTEM" I start to cry. Planets ARE NOT the entire thing. Solar System has dynamics and mystery which goes well beyond just the biggest rocky/gaseous balls. And knowing the NAME of a planet does not tell ANYTHING about the planet itself.

You can teach the name of the planets with a catchy poem and imagine how Disney has its own planet out there. Woo-haa.
You can teach that the first president of USA (after Constitution) was Washington and World War II was fought in 1939-1945.

OR

You can teach WHAT the Solar System is, and HOW and WHERE. That it has a central star (and what a star actually is), bigger planets (both gas and rock) with moons, asteroid belt, smaller planets and comets further away from the star and Kuiper Belt etc etc. And that some moons have geysirs, atmospheres, underground oceans and how this all has been formed and what is our place in the universe. Suddenly it does not seem too important anymore to argue what is the cherry and what is the cream of the cake.

You can also teach what things lead into the World War II or to the independence of United States and all the other things around them, the mistakes, the choices, the politics, the personalities. Does it sound too important anymore to just memorize some years and numbers and leader names anymore? Would that teach us actually anything?

(I do not judge or criticize any particular school system because I really dont know any outside our own here behind the back of the creator, but at least I have been taught in the school the latter way. Which I am very grateful of.)

Science is a thing which develops. 1801 we had Mercury-Venus-Earth-Mars-Jupiter-Saturn-Uranus. Then BOOM we have Ceres. If the situation would be today the same, of course Ceres would be a planet... BUT. After a few decades we had found more and more of these "cereses" and found out that heyy, there's actually a wholelottathem so maybe Ceres is NOT a planet but more like these "other things" out there. So, Ceres no more planet. Afterwards we find out it was a right call. Then came Neptune, that was easy to put among its kind, so a planet. Then time passes. Happens Ceres round 2. We find Pluto. Hmm... it is 6 000km's in size (early estimates...) so it must be a planet right? Ok, good. We find Charon and get more detailed estimates of size... hmmm... this Pluto might not be a planet after all, but whatttaheck, let's keep it there still just to be sure. Then comes new KBO findings and finally Eris & pals. So, we are exactly in the same situation as after few decades when they had found Ceres. And again, we see that Pluto is part of its gang out there, KBO's etc. NOT among "normal planets". So, we should recognize that and accept that Solar System has different gangs. Gang of big gaseous ones, gang of big rocky ones, gang of asteroids, gang of KBO's, gang of comets... If you wanna and must have dwarf planet category, fine, have it and start to fill the list, but do these dwarf planets actually have anything in common? Can e.g. Ceres and Eris go under same title? I clearly see similarities between Mercury-->Mars and also Jupiter-->Neptune (compositions, location...) and then there are comets, asteroids, KBO's but please define me dwarf planet...

Wouldn't it be better just say that beside 8 planets there is asteroid belt, with biggest member of them being Ceres? That there is Kuiper Belt, with biggest members being Eris and Pluto/Charon? That there might be Oort Cloud, and biggest member so far being Sedna? Would it be too hard (read:scientific & accurate) and too unsexy to teach that at schools or read that from publications?

This sort of teaching and relaxed (still scientifically valid) categorization would not even pose a problem when we start to map these exo-systems with again totally new sort of planets and solar system objects. We could just say that ok, in this particular solar system thing are like this, and in that system things are like that. We would not have to lose the credibility of science by resetting all the books and terms every few years when we find something new. At the moment it feels like astronomy has some sort of "Windows update" -curse going on.

I know that for some people categories mean more than substance but please, putting emotions before practicality and science is not really helping anyone in the long run. Keeping Pluto as a planet would end up being just an exception nobody could actually never justify or explain to their children. "Yes it is wrong but let's keep it wrong because that has been the tradition." Sounding Soviet, anyone...? At the 19th century people propably had more balls when they made the call to demote Ceres. I raise my hat for those brave pioneers.

PS. I still believe that if Mickey Mouse had a dog named Rex, we wouldn't even have this emotionally flaming debate going on...

...I raise my hat to you, K-P! Brilliant post.

All I can add are four words: Subjective. Subjective. Subjective. Emotional.

Think that's just about the correct ratio for this debate. I've tried to call in Mr. Spock for mediation from a purely logical viewpoint, but can't get a good number. (I think he's ducking me, frankly.)

A couple of people have complained that this thread has been repeating arguments. I definitely have read some new and useful points in the past couple of days, but there is a lot of repeated ground here. I don't know if a FAQ (without facts?) or a Wiki handles it better than a list. At least to put things to the point of "Here is observation X, which has attracted support Y and rebuttal Z."

For example, the idea of an exception being problematic is often rebutted with the observation that Europe's status as a continent is a broadly-accepted analogue. Then if there's a rebuttal to that, let it so be noted. And if we get to an observation without a rebuttal, then everyone has to end up unanimously convinced -- right?

...and personally I have always felt that Europe as a "continent" is not a proper expression. Eurasia is. And without that artificial Suez-canal I would prefer even more Afro-Eurasia. Culturally Europe is an area. Yes. Nationally. Yes (European Union). Geographically there is a european peninsula (some sort of), but a true continent it is not, so let it be removed from that list of continents. Please.

Garg. I'm officially done with this entire debate now, and really don't care what a planet is. All I know is that I live on one, would like to visit others, but won't live long enough to be able to do so, unfortunately. Thank you, and goodnight!

So the question arises; is Australia a continent? While it has obviously achieved geometric equilibrium, it certainly hasn't cleared it's "neighborhood." Or do New Guinea and New Zealand count as continental satellites? All those other smaller islands are troubling, though. Maybe "dwarf continent" would be more appropriate.

Don't change your dreams, change the terms. Maybe if Texas would be called a planet, you would also live long enough then...?



(duck... and cover...)

...I've been to Texas many times. And, yeah, it's sorta like visiting another planet in some ways. Texas is really just a state of mind.

(Let me just hang that thought up here, pregnant with possibilities...)

I hereby claim the continent analogy for the state of despair. Or the state of arguing in circles, which I think was my original point.

And Stu, I thought rubbish was a noun? You've adjectived it.

Personally, with any argument that the definition needs to be simple, or the list short, I think there is way too much worry over people that just won't care one way or the other. Might trigger a few fleeting short-term synapses, but you're not making an impression. And if you do make an impression, they'll quickly gather that reality is a lot more interesting than a bulleted list.

It is, and I did. It's a Brit thing.

I second everything that Stu said. We underestimate children's capabilities when we assume they are incapable of understanding that there is a controversy between scientists holding two different perspectives or that sometimes we just need to wait for more data to come to a definitive conclusion. At the Great Planet Debate, NASA lessons on teaching this at the level of grades 2-5 and 9-12 were distributed along with exercises for the students to do to help them understand the controversy. For example, at the high school level, a hypothetical case of a new planet is presented, and students are asked to consider the facts, come to their own conclusions and then hold a debate. In evaluating the debate, the teacher looks for clear articulation of ideas, sound reasoning, rebuttal skills, etc.

As a "Plutophile," I--and I am guessing most others--are not wedded to teaching nine planets. Most of us have no problem with the solar system having 50, 100, 200 or more planets. What we object to is the limiting of the term planet to only those objects that dominate their orbits. Instead, we seek to use the quality of hydrostatic equilibrium as a broad measure to determine planethood since that is where differentiation and geophysical processes start to take place. This doesn't mean that we cannot distinguish planets based on dynamical characteristics through the use of subcategories. What this means is that the demotion of Ceres--and of Pluto and Eris--was in fact not a right call. Nineteenth century astronomers did not know that because they were incapable of imaging Ceres. During the 1990s, Hubble images showed that Ceres is round and definitely in a state of hydrostatic equilibrium. So if we use the hydrostatic equilibrium criterion, which many believe is the best because it is something everything ranging from giant to dwarf planets have in common--putting Pluto in the planet category does not make it an exception, just one of many in the dwarf planet subcategory.

This is not based on emotion, sentiment, or on Mickey Mouse's dog but on a genuine conviction by many planetary scientists and lay people as to what is the best classification method for objects in this and other solar systems. Yes, to a certain extent, every human being is subjective and emotional when it comes to issues about which they care a great deal. No one on either side of this debate can claim to be completely free of emotion about it; even Spock, being half human, couldn't do that. In fact, the sense of romance and excitement Stu experiences in observing the night sky is something that is contagious; kids pick up on it; they get excited about viewing objects like Jupiter and Saturn, and for some of them, it may be a first step towards a career in astronomy.

In summary, the existence of emotions on both sides does not change the fact that there are legitimate scientific arguments in favor of keeping the term planet broad while recognizing the differences among the many subclasses of planets through establishing multiple subcategories.

Interestingly, I did a quick web-search for this topic, to find some content to point to as a shell of the "FAQ" and found a nice expression of the pro-Europe sentiment... by Mike Brown, on a heavily-edited webpage (where he left some of the original copy mixed in with the edits) at:

http://www.gps.caltech.edu/~mbrown/planetlila/

But I cite this just to suggest that rather than repeat 9 steps in the argument ago and then wait foot-tapping for someone else to repeat 8 steps ago, and make this truly pointless, that we at least have a "reading list" of positions and then keep things on the topic of moving ahead instead of in circles.

It certainly doesn't sound nice to be underestimating children or calling them incapable, but it is true that certain lessons will shoot over certain kids' heads. Or get the "Mensa" kids engaged while losing the rest. And I think eye contact is often mistaken for engagement. I'd at least ask myself if all the students in the room understand why some parts of the Moon are full of craters, while other parts have fewer, and the Earth has fewer still, before this issue bubbled to the top of the list.

Maybe other people can think of better examples, but I have always been fond of Nick Hoffman's arguments for a White Mars (with CO2 playing the role that others suspect water to be playing). THAT is an example of a scientific debate. That is science at work, right or wrong. And it's impossible to follow it without learning some interesting things about Mars.

This planet issue isn't a scientific debate. It's scientists engaged in a non-scientific debate. It's like using a Jerry Springer episode to teach people American history instead of talking about Jefferson or Lincoln. The "White Mars" debate teaches the useful lesson that scientists don't always know the answer. The planet-definition debate teaches the lesson that scientists don't always know when they're outside their depth.