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Unmanned Spaceflight.com _ Pluto / KBO _ The Great Planet Debate conference

Posted by: Alan Stern Aug 10 2008, 03:17 PM


You probably already know about The Great Planet Debate meeting coming this week near DC, if not, see:
gpd.jhuapl.edu.

To register for Great Planet Debate conference web participation, click: http://tinyurl.com/6xcqec
Watch the talks and debate on line!

-Alan

Posted by: ElkGroveDan Aug 10 2008, 04:11 PM

Thanks Alan. The whole issue hit home with me this week when I was talking to my kids about planets and my five-year-old daughter corrected me and and said "Pluto is not a planet. My teacher told me that." I'll be glad to see the discussion opened up again in a serious forum.

Posted by: Hungry4info Aug 10 2008, 06:10 PM

Forgive the, perhaps ignorant question... but do the people at this coming debate have the authority to change the status of Pluto? i.e. change what objects are planets, and what objects are dwarf planets? I'm guessing "No.", but am not sure.

Posted by: djellison Aug 10 2008, 06:13 PM

Nobody can change what these planets 'are'.

But they can try and come up with a better way of categorizing them - the current system is utterly broken (and that's coming from someone who doesn't care if Pluto is a planet or not,I just want a definition that makes sense)

Doug

Posted by: ngunn Aug 10 2008, 09:47 PM

QUOTE (djellison @ Aug 10 2008, 07:13 PM) *
I just want a definition that makes sense


Unfortunately that might just be 'pie in the sky' (that would cover pizza moons as well). wink.gif

Posted by: Greg Hullender Aug 11 2008, 03:43 PM

QUOTE (djellison @ Aug 10 2008, 10:13 AM) *
But they can try and come up with a better way of categorizing them - the current system is utterly broken (and that's coming from someone who doesn't care if Pluto is a planet or not,I just want a definition that makes sense)


I'm still liking Mike Brown's thinking on the matter:

http://www.mikebrownsplanets.com/ (scroll down to "Ground rules for debating the definition of 'planet'")

He says he personally considers the debate closed, but since we don't seem to be able to move on, he proposes some rules for the discussion.

There's a lot of good stuff here, but this struck me as new information:

QUOTE
Misleading statements about the previous vote should also be disallowed. Yes, the whole IAU procedure was a bit mucked up, but the results would likely have been the same no matter who was in the room at the time. Surveys done after the IAU vote – yes there were some! – showed that astronomers by a large number thought that the 8 planets definition was a good one. So complaining about the IAU vote gets you the label of “misinformed about how most astronomers think."


I thought that was a particularly strong claim. I wonder who does those surveys? :-)

--Greg

Posted by: Alan Stern Aug 11 2008, 04:23 PM

I'd sure like to know too. The only one I know of is the Sykes-Stern petition, which in 48 hours after being introduced gained 300+ signatories who were displeased with the IAU vote.

Brown's assertion that the vote "would" have been the same is unsupported.

Worse, voting in science is about the worst way one can go: can you imagine if there were voting on evolution, global change, etc.? Voting is antithetical to science, which works by archieving consensus based on which models best fit an ever expanding base of data.

Anyway, The GPD later this week in Maryland will feature debate and no votes. Come to the meeting or tune in if you can't and are interested.

-Alan

QUOTE (Greg Hullender @ Aug 11 2008, 04:43 PM) *
I'm still liking Mike Brown's thinking on the matter:

http://www.mikebrownsplanets.com/ (scroll down to "Ground rules for debating the definition of 'planet'")

He says he personally considers the debate closed, but since we don't seem to be able to move on, he proposes some rules for the discussion.

There's a lot of good stuff here, but this struck me as new information:



I thought that was a particularly strong claim. I wonder who does those surveys? :-)

--Greg

Posted by: tedstryk Aug 11 2008, 04:47 PM

It reminds me of how Stephen Colbert decides whether an idea is right or wrong based on how well it sells. For example, he changed positions on global warming because Al Gore's book sold more copies than those written to oppose his position (for those outside the U.S., the Colbert Report is a parody news program).

Posted by: Hungry4info Aug 11 2008, 06:50 PM

Okay, I'll ask my question in a different way:

Do the people at this coming debate have the authority to change the status of Pluto?

i.e. if the people at this debate want to call Pluto a planet, will Pluto be called a planet? Regardless of what it is.

Posted by: Mongo Aug 11 2008, 06:50 PM

QUOTE (Alan Stern @ Aug 11 2008, 04:23 PM) *
Worse, voting in science is about the worst way one can go: can you imagine if there were voting on evolution, global change, etc.? Voting is antithetical to science, which works by archieving consensus based on which models best fit an ever expanding base of data.


I agree. However, in this case the debate is over terminology, not science. In my own opinion (for what it is worth), the term 'planet' is obsolete and should be retired. I would go with several sets of terms for each type of object: a set of terms for composition -- 'gas giant', 'ice giant', 'terrestrial' and 'ice dwarf'; a set of terms for orbital status -- orbiting the Sun, orbiting another body that in turn orbits the Sun, or in a mean-motion resonance with a more massive Sun-orbiting body; and a set of terms for gravitational self-rounding (including non-typical objects like 2003 EL61) -- fully gravitationally relaxed, partially relaxed, unrelaxed.

So Pluto would be a fully gravitationally relaxed ice dwarf in a mean-motion resonance with a more massive Sun-orbiting object.

Luna would be a fully gravitationally relaxed terrestrial orbiting a more massive Sun-orbiting object.

Vesta would be a partially gravitationally relaxed terrestrial orbiting the Sun.

And so on.

Posted by: Alan Stern Aug 11 2008, 07:16 PM

QUOTE (Mongo @ Aug 11 2008, 07:50 PM) *
I agree. However, in this case the debate is over terminology, not science. In my own opinion (for what it is worth), the term 'planet' is obsolete and should be retired. I would go with several sets of terms for each type of object: a set of terms for composition -- 'gas giant', 'ice giant', 'terrestrial' and 'ice dwarf'; a set of terms for orbital status -- orbiting the Sun, orbiting another body that in turn orbits the Sun, or in a mean-motion resonance with a more massive Sun-orbiting body; and a set of terms for gravitational self-rounding (including non-typical objects like 2003 EL61) -- fully gravitationally relaxed, partially relaxed, unrelaxed.

So Pluto would be a fully gravitationally relaxed ice dwarf in a mean-motion resonance with a more massive Sun-orbiting object.

Luna would be a fully gravitationally relaxed terrestrial orbiting a more massive Sun-orbiting object.

Vesta would be a partially gravitationally relaxed terrestrial orbiting the Sun.

And so on.


Mongo-

Since planetary science is a field and planetary scientists have a profession, I do not think we can or want to retire the term which planets. Instead, our field and our profession need to come to a consensus on what we, the practitioners, consider to be planets vs. smaller and vs. larger things. That astronomers hijacked this process is about equivalent to brain surgeons, rather than cardiologists, deciding where the dividing lines between veins, arteries, and capillaries are, and the public/press following along because "they are all doctors, after all."

As to Hungry4Info's question, no one really has the authority to change the status of Pluto or other bodies. Science doesn't work by such decrees-- it works by finding the best solution that fits the data, which is fundamentally about achieving consensus, not votes or decrees.

Hope this helps.

-Alan

Posted by: surreyguy Aug 11 2008, 07:45 PM

QUOTE (Alan Stern @ Aug 10 2008, 04:17 PM) *
To register for Great Planet Debate conference web participation, click: http://tinyurl.com/6xcqec
Watch the talks and debate on line!

-Alan


Are we able to participate in the conference as a whole, then? I have registered, but I thought all that gives me is the chance to hear Sykes and Tyson duke it out. I look forward to that, but my expectation is of more heat than light to be honest.

Posted by: Alan Stern Aug 11 2008, 08:03 PM

QUOTE (surreyguy @ Aug 11 2008, 07:45 PM) *
Are we able to participate in the conference as a whole, then? I have registered, but I thought all that gives me is the chance to hear Sykes and Tyson duke it out. I look forward to that, but my expectation is of more heat than light to be honest.



I believe all the invited talks will be posted as videos and the slide presentations from most or all of the talks at the entire meeting will also be posted. That said, I am not a meeting organizer and cannot vouch this is absolutely correct. As to Sykes/Tyson, I am hoping for a more scientific debate, but knowing both and considering both fiends for 20+ years, I will say I do expect some entertaining barbs too!

-Alan

Posted by: Greg Hullender Aug 11 2008, 08:19 PM

QUOTE (Alan Stern @ Aug 11 2008, 12:03 PM) *
knowing both and considering both fiends for 20+ years, I will say I do expect some entertaining barbs too!


Gee . . . they seem so nice on TV!

--Greg :-)

Posted by: Greg Hullender Aug 11 2008, 08:57 PM

QUOTE (Alan Stern @ Aug 11 2008, 11:16 AM) *
Since planetary science is a field and planetary scientists have a profession, I do not think we can or want to retire the term which planets.


That's actually a very powerful argument I haven't really heard before -- that the scientific definition of planet should correspond to "worlds that have geology," because that's what Planetary Scientists study. That means, though, that our Solar System has about thirty planets, since this includes our moon and about seventeen other moons on top of the magic eight and the four dwarves. (Or am I completely confused? You're the real Planetary Scientist here.) :-)

Sometimes it does seem that all the counterarguments to this definition really boil down to "but what will we tell the children?" A fair point could be made that the definition should serve scientists -- not school kids -- given that there are in fact scientists to whom it's useful.

--Greg



Posted by: surreyguy Aug 11 2008, 09:00 PM

Ah, that'll be good, if so. Keep me out of (or in) mischief for the weekend.

Posted by: surreyguy Aug 11 2008, 09:09 PM

QUOTE (Greg Hullender @ Aug 11 2008, 09:57 PM) *
That's actually a very powerful argument I haven't really heard before -- that the scientific definition of planet should correspond to "worlds that have geology," because that's what Planetary Scientists study.


Well, only if you accept that geology is what planetary scientists study in the first place. Presumably dynamicists think they study planets, too, and opt for the dynamical definition. I'd agree with you, though, that if supporters of the hydrostatic definition pressed to abolish the satellite, their position would be a lot more clear.

I think if planetary scientists manage to define their own profession, that'll be a world first. In my own, erm, 'profession', operations research, it's a standing joke that if you put two OR people in a room, you'll get three definitions of OR. Now let's just ask the biologists for a definition of 'life'...

Posted by: Greg Hullender Aug 11 2008, 10:01 PM

QUOTE (surreyguy @ Aug 11 2008, 02:09 PM) *
Well, only if you accept that geology is what planetary scientists study in the first place.


No, I said they study worlds that have geology. Now if, in fact, they actually study the stars and the dust and everything in between then it's much harder to argue that they need a scientific definition of "planet".

--Greg

Posted by: djellison Aug 11 2008, 10:20 PM

I was worried this would turn into another 'define-a-body' argument, because we've really had enough of that here. But wow - we've got a new one, define-a-debate. Debating who can debate it is a nice new twist...I like it.

Doug

Posted by: surreyguy Aug 11 2008, 10:20 PM

OK, I get you. We seem to be straying off 'Dwarf Planet Eris' so I'd better stop.

Posted by: JRehling Aug 11 2008, 10:41 PM

The "authority" issue is a relevant one. If you like a particular kind of music, and a panel of experts convened and came out saying that the term you'd always used to describe it was invalid, would you stop using it? If there were a cartographical definition that discriminated between hills and mountains and you saw a protuberance whose height was unknown to you, would you pause mid-sentence out of uncertainty which term was correct?

Part of the issue here is the relationship between folk uses of terms and expert uses. Look up "star" in any dictionary and, besides the terms referring to actors, you find one astronomical definition denoting large gaseous spheroids heated by fusion and another denoting small, twinkling lights in the sky. By the latter definition, the percept Jupiter makes in the night sky is aptly labeled a "star".

One of the things that concerns me most is when a naive viewer of the night sky asks a question about a "star" and is told snippily that they just displayed their ignorance -- that what they are looking at is not a star. I don't think many people get very far in life without having some encounters like that, and the take-home lesson is that science equals pedantry and poor manners to boot. And I think the whole notion of the IAU defining "planet" gives that perception a giant shot in the arm.

When it comes right down to it, the "twinkling pointlike source of light" is *a* perfectly fine definition of the word "star" that doesn't supplant the scientific one, but exists for another context. And my perspective on that hypothetical encounter is that the pedant is actually the one displaying ignorance.

Cue the "planet" debate: While the lay-experience with planets is much less frequent than with stars, I'd say the folk experience (in schools, in backyards, watching science fiction movies) is still extensive enough to consider the term to have a folk sense. Meanwhile, it has absolutely no useful scientific sense. Saturn and Mars obviously have less in common than Pluto and Triton.

So I find the whole thing to be that backyard experience writ large: There's a kind of arrogance behind it, and it says to the world that pedantry is really what science is up to. If some jazz counsel had a vote on whether or not Miles Davis played jazz, I wouldn't care if the vote were 51-49 or if it were 100-0 -- I'd still keep calling it jazz. Far from caring about which side of which line Pluto is placed, I consider this a battle against pedantry, which, if won unbloodily, might mean more people who care about science.

Posted by: alan Aug 11 2008, 11:19 PM

QUOTE (Greg Hullender @ Aug 11 2008, 10:43 AM) *
I'm still liking Mike Brown's thinking on the matter:
http://www.mikebrownsplanets.com/ (scroll down to "Ground rules for debating the definition of 'planet'")
There's a lot of good stuff here, but this struck me as new information:

-Greg

I found this quote about Nature and Science from his latest post interesting
QUOTE
along with publishing important ground-breaking papers appears to come the requirement that a larger than usual fraction of the conclusions published in these journals turn out to be incorrect. This leads to the semi-joking line that you often hear amongst astronomers: “Just because it is published in Nature doesn’t necessarily mean that it is wrong.”

Posted by: Greg Hullender Aug 11 2008, 11:50 PM

QUOTE (JRehling @ Aug 11 2008, 02:41 PM) *
One of the things that concerns me most is when a naive viewer of the night sky asks a question about a "star" and is told snippily that they just displayed their ignorance -- that what they are looking at is not a star. I don't think many people get very far in life without having some encounters like that, and the take-home lesson is that science equals pedantry and poor manners to boot. And I think the whole notion of the IAU defining "planet" gives that perception a giant shot in the arm.


I think we definitely need to restrict the debate to exclude people who can't tell the difference between planets and stars. I realize this will hurt their feelings, but I just don't think it can be helped.

--Greg :-)

Posted by: Alan Stern Aug 12 2008, 12:56 AM

QUOTE (Greg Hullender @ Aug 11 2008, 09:19 PM) *
Gee . . . they seem so nice on TV!

--Greg :-)


I really need to learn to type, it's going to limit my career if I don't.

Posted by: Alan Stern Aug 12 2008, 12:59 AM

QUOTE (Greg Hullender @ Aug 11 2008, 09:57 PM) *
That's actually a very powerful argument I haven't really heard before -- that the scientific definition of planet should correspond to "worlds that have geology," because that's what Planetary Scientists study. That means, though, that our Solar System has about thirty planets, since this includes our moon and about seventeen other moons on top of the magic eight and the four dwarves. (Or am I completely confused? You're the real Planetary Scientist here.) :-)

Sometimes it does seem that all the counterarguments to this definition really boil down to "but what will we tell the children?" A fair point could be made that the definition should serve scientists -- not school kids -- given that there are in fact scientists to whom it's useful.

--Greg


30, 300, 3000-- it's whatever Nature tells us. No one limits the numbers of rivers, streams, elements, mountains, stars, etc. just for the convenience of memory. That argument is anti-scientific, and, I think, a dodge.

Alan

Posted by: Juramike Aug 12 2008, 01:07 AM

QUOTE (Greg Hullender @ Aug 11 2008, 07:50 PM) *
I think we definitely need to restrict the debate to exclude people who can't tell the difference between planets and stars. I realize this will hurt their feelings, but I just don't think it can be helped.

--Greg :-)


Uhhhmmmm....Brown dwarf? smile.gif smile.gif

Is the http://ttp://en.wikipedia.org/wiki/Brown_dwarf a widely known thing among most people?

My point is that there is a continuum between all things. The minute you define something, you will find yourself with an exception or special case that is difficult to assign. As our detection methods get better, these special cases can multiply beyond control and you get real cumbersome definitions and special rules that don't help very much - I kinda think we're there now with the whole "planet" definition thing. We probably do need an extensive series of categories that span the whole range of things we know about, and of things we probably haven't even discovered yet.

What will you call a world that orbits an unassociated brown dwarf
What will you call a world that orbits a gas cloud?
What will you call co-orbital worlds?
What will you call twinned worlds that orbit each other?
What will you call worlds that switch orbits periodically?

For all we know, these things could be more common than our own solar system.

For the Great Debate whether Pluto is a "planet" or not, I'm not vehement one way or the other. It will work itself out over the years as we get a better idea of the spectrum of "object relationships" from both observational (extrasolar detections) and theoretical modelling (since there will be limits on what we can detect).

Heck, I'm still struggling with the definition of "terrestrial world". Which is more similar to Earth: Mercury or Titan?

-Mike

Posted by: nprev Aug 12 2008, 01:19 AM

Totally agree, Mike; said it before & I'll say it again, natural things exist along a continuum.

(I call this the "Platypus Argument"). tongue.gif

Posted by: Greg Hullender Aug 12 2008, 01:38 AM

QUOTE (Alan Stern @ Aug 11 2008, 05:59 PM) *
30, 300, 3000-- it's whatever Nature tells us. No one limits the numbers of rivers, streams, elements, mountains, stars, etc. just for the convenience of memory. That argument is anti-scientific, and, I think, a dodge.

Alan


Oh I didn't mean to appear to be arguing that 30 was too many. Just making sure we agreed that "orbiting a star" wasn't a reasonable part of the definition as far as "what planetary science studies" goes.

I am right on that part? The "planets" that planetary science studies are exactly those bodies in hydrostatic equilibrium, right? Not dust and not stars, but definitely including moons, if they're big enough. It's all about what they are -- not where they are.

--Greg

Posted by: Alan Stern Aug 12 2008, 01:42 AM

QUOTE (Greg Hullender @ Aug 12 2008, 02:38 AM) *
Oh I didn't mean to appear to be arguing that 30 was too many. Just making sure we agreed that "orbiting a star" wasn't a reasonable part of the definition as far as "what planetary science studies" goes.

I am right on that part? The "planets" that planetary science studies are exactly those bodies in hydrostatic equilibrium, right? Not dust and not stars, but definitely including moons, if they're big enough. It's all about what they are -- not where they are.

--Greg


Greg--

I completely agree and will argue so in my invited talk at GPD. Whether bound to a star, bound to another planet, or just floating through the ISM, I am good with it as a planet so long as it has the central attributes of planethood-- large enough to be in HSE but not so massive that it does/never did fusion in its interior. An Earth in orbit around a Jupiter or escaped from its sun is still a planet, just as much a star is a star whether orbiting another star or even escaped from a galaxy.

-Alan

Posted by: Greg Hullender Aug 12 2008, 01:54 AM

QUOTE (nprev @ Aug 11 2008, 06:19 PM) *
Totally agree, Mike; said it before & I'll say it again, natural things exist along a continuum.

(I call this the "Platypus Argument"). tongue.gif


But the logical conclusion of this argument is that there's no such thing as science; everything is unique, and studying patterns is wrong. You SURE you want to ride this train? :-)

--Greg

Posted by: Alan Stern Aug 12 2008, 01:57 AM

QUOTE (Greg Hullender @ Aug 12 2008, 02:54 AM) *
But the logical conclusion of this argument is that there's no such thing as science; everything is unique, and studying patterns is wrong. You SURE you want to ride this train? :-)

--Greg


No, everything is unified. Planets are a class of bodies bigger than boulders and rubble piles but smaller than stars. ...Unless I miss your point, this is unifying, and a fine train to ride.

Posted by: Juramike Aug 12 2008, 02:17 AM

QUOTE (Greg Hullender @ Aug 11 2008, 08:54 PM) *
But the logical conclusion of this argument is that there's no such thing as science; everything is unique, and studying patterns is wrong. You SURE you want to ride this train? :-)

--Greg


Well, you can bin things. But sometimes things can go in more than one bin.

[A slightly off-topic example: Stromatolites were originally assigned species. But as time goes on, it appears that stromatolites are fossilized microbial mats that may have resulted from several species. A newer classification system is based primarily on shape and structure of the stromatolite, totally ignoring the microbe that created it.]

[Another case: Early stage cancer is not a specific disease. It is a member of a matrix of disorders, with an initial gene defect causing loss of cellular control in one vector, and the tissue type in another. Once this is realized, the War on Cancer will not be fought on a single front, but as a multitude of small skirmishes. (Metastatic cancer is, unfortunately, most of the full matrix)]

[Another example: Biological science is famous for uncovering a new receptor or enzyme. Usually, further examination reveals a whole plethora of enzymes. Serotonin receptors are a great example. There are over 13 different serotonin receptors. There is even a naming committee for these receptors (with back-and-forth arguments as well.) One of my favorite quotes is "Note that there is no 5-HT1C receptor since, after the receptor was cloned and further characterized, it was found to have more in common with the 5-HT2 family of receptors and was redesignated as the 5-HT2C receptor." ]

The beauty of studying the patterns is that there are so many different ways to group things.

Remember the "http://www.youtube.com/watch?v=tZIvgQ9ik48" song on Sesame Street? I was the kid always trying to find a relationship to group the "obvious exception" choice back in and exclude one of the other objects.

-Mike

[EDIT: found a Cookie Monster video clip]

Posted by: nprev Aug 12 2008, 02:32 AM

QUOTE (Alan Stern @ Aug 11 2008, 05:57 PM) *
No, everything is unified. Planets are a class of bodies bigger than boulders and rubble piles but smaller than stars. ...Unless I miss your point, this is unifying, and a fine train to ride.


I'm flattered! smile.gif

One thing to keep in mind is that categories are a human invention, a very useful way for us to rationally perceive the Universe and discern relationships, as Mike pointed out. Nature does not sort itself; we do the sorting.

IMHO, the only things that sort themselves into completely discrete and unique (though identical within each category) entities are subatomic particles. It is a marvel to contemplate the fact that such simplicity at such a small level (possibly down to the mere six flavors of quarks) can be organized at macroscales into the diversity of things in the Universe.

Posted by: Greg Hullender Aug 12 2008, 03:44 AM

QUOTE (Alan Stern @ Aug 11 2008, 06:57 PM) *
No, everything is unified. Planets are a class of bodies bigger than boulders and rubble piles but smaller than stars. ...Unless I miss your point, this is unifying, and a fine train to ride.


Yeah, you miss my point. ;-)

I'm okay with the "Planetary Science" train. I'm not okay with the "Ignorance Eternal" train.

The former is the one that says "planets are what planetary science studies . . ." and all that follows from that.

The latter is the one that says "everything is a continuum; all entities are unique; we cannot ever know more or say more about anything." Did you see the "platypus" reference? This is the logic that argues "the term planet is meaningless -- and even the term MAMMAL is meaningless."

--Greg

Posted by: nprev Aug 12 2008, 04:34 AM

QUOTE (Greg Hullender @ Aug 11 2008, 07:44 PM) *
Did you see the "platypus" reference? This is the logic that argues "the term planet is meaningless -- and even the term MAMMAL is meaningless."


Not meaningless; merely artificial, and (literally) an artifact of the way we perceive the Universe.

We need points of reference to make sense of things & determine relationships. "Mammal" is a pretty good distinction, but the platypus is a great example of a borderline case. Nature is not bound to what we say it should be or not is all I'm saying. There are literally no true dichotomies in the natural world.

Biology offers abundant examples: slime molds are a beaut. It gets even worse when considering microorganisms, in fact. Under some taxonomies, we're up to five, count 'em, five distinct kingdoms of life...a pronounced increase from the traditional two of plant & animal that we all know from school.

Only point I'm making is that whatever the outcome of the GPD might be, and even if a consensus emerges, it'll be pretty much subjective at the core. There aren't any absolute distinctions that can be made. Moreover, as Mike again pointed out, we'll find objects someday that will challenge any definition we might make. (My personal fav in the near-term is finding a Mars-sized or better KBO 1000AU or more out...)

In all likelihood, it will be an eternal debate, and certainly not restricted to astronomy. Imagine what might happen if someday we find a complex alien ecosystem... rolleyes.gif ...oy, vey!!!

Posted by: volcanopele Aug 12 2008, 04:34 AM

Don't forget that planetary scientists also study moons, asteroids, comets, dwarf planets, Trans-Neptunian Objects, etc. We don't just study planets wink.gif

Posted by: lyford Aug 12 2008, 05:07 AM

Ok, so if a planetary scientist were less than 5 ft. in height... no I don't really want to go there. huh.gif

Posted by: dvandorn Aug 12 2008, 06:17 AM

QUOTE (JRehling @ Aug 11 2008, 05:41 PM) *
The "authority" issue is a relevant one. If you like a particular kind of music, and a panel of experts convened and came out saying that the term you'd always used to describe it was invalid, would you stop using it? If there were a cartographical definition that discriminated between hills and mountains and you saw a protuberance whose height was unknown to you, would you pause mid-sentence out of uncertainty which term was correct?

Ah, but that kind of thing goes on all the time. Music is redefined into different catagories as time passes and it is seen in context with its moment(s) in history. And, of course, *anything* that is categorized as "modern" is doomed to be renamed as it fades into the more and more distant past.

Much moreso, far more basic categorizations and names change constantly. Meet anyone from Stalingrad lately? Or someone who lives in Czechoslovakia? Or Persia? Just ask the Poles -- they've gone through periods in history when their entire country ceased to exist, for decades and more at a time. Or the Slavs in general, who were enslaved so many times by so many conquerors that the very name of their ethnicity entered many languages as the definition of the very concept of slave.

How different is it to go to sleep in the Soviet Union and wake up in the independent state of Kazakhstan than it is to go to sleep in a solar system with nine planets and wake up in one with eight? Or 30? Or 3,000?

Things change as time goes on, and as they change we have more and more information -- more and more history -- that puts bits and pieces of our Universe into a new context. From whether the world calls it Peking or Beijing to whether Pluto is called a planet, a dwarf planet, an icy dwarf, or a cartoon dog.

This way we have of changing/refining the categories as we learn more and put things into better and better context helps us understand and come to terms with our place in the Universe. And as the old saw goes, it's not an event, it's a process. What is debated today and decided tomorrow will inevitably be re-interpreted, re-debated and re-decided over and over as time goes on. The best thing we can do, exactly as Alan has said, is try to attain a consensus that satisfies the maximum number of people, that is driven by relatively rational principles, and that reflects our *best* understanding of the science involved.

-the other Doug

Posted by: JRehling Aug 12 2008, 06:54 AM

QUOTE (Greg Hullender @ Aug 11 2008, 04:50 PM) *
I think we definitely need to restrict the debate to exclude people who can't tell the difference between planets and stars.


It can be pretty hard to tell the difference between Saturn and Regulus in a lot of circumstances.

Through a car window in the growing light of dawn, when you're uncertain which way is due north, etc.

And try spotting Uranus without mechanical assistance and see if you're immediately sure which magnitude 5.8 object it is.

It can be pretty hard to come away from the context of looking at books and articles, but there is a real world of lights and sounds, and it's in that context where the "pointlike source of light" definition of star is perfectly useful. So you don't have to say things like, "There, in Capricorn, between the two pointlike sources of light which could be either stars or perhaps one of them is Uranus or even Vesta or a dim comet..." A word of one syllable comes in pretty handy.

Posted by: dvandorn Aug 12 2008, 07:09 AM

QUOTE (JRehling @ Aug 12 2008, 01:54 AM) *
It can be pretty hard to come away from the context of looking at books and articles, but there is a real world of lights and sounds, and it's in that context where the "pointlike source of light" definition of star is perfectly useful. So you don't have to say things like, "There, in Capricorn, between the two pointlike sources of light which could be either stars or perhaps one of them is Uranus or even Vesta or a dim comet..." A word of one syllable comes in pretty handy.

Which takes us back to the very origin of the word planet. Back in the days when the only way we could chart the seasons and predict celestial events was to examine the sky and the stars. Some of the most revered astronomers of the early ages spent lifetimes plotting the movements of the stars in the heavens. And while most stars moved in easily predictable patterns, some of them -- and indeed, some of the brightest of them -- moved in odd and eldritch fashions, passing through the static and unchanging constellations in non-intuitive, hard-to-predict patterns that repeated (with major variations) over the course of months in some cases, or over the course of decades in others.

These were the planetes, the wanderers.

So, the original meaning of the term had absolutely nothing to do with the physical characteristics of the bodies. It only referenced the different way in which they traversed our skies from all of the other stars.

As I said, as time goes on, context changes...

-the other Doug

Posted by: JRehling Aug 12 2008, 07:12 AM

QUOTE (dvandorn @ Aug 11 2008, 11:17 PM) *
Ah, but that kind of thing goes on all the time. Music is redefined into different catagories as time passes and it is seen in context with its moment(s) in history. And, of course, *anything* that is categorized as "modern" is doomed to be renamed as it fades into the more and more distant past.

Much moreso, far more basic categorizations and names change constantly.


Yes, but it's also resisted all the time and ignored all the time. And it's potentially a battle of wills between the would-be authorities and the public; sometimes the battle easily goes one way, and sometimes easily the other way. E.g. (thanks again, Wikipedia).

http://en.wikipedia.org/wiki/Name_of_Pittsburgh

"On December 23, 1891, a recommendation by the United States Board on Geographic Names to standardize place names was signed into law. The law officially changed the spelling of the city name to Pittsburg, and publications would use this spelling for the next 20 years. However, the change was very unpopular in the city, and several businesses and organizations refused to make the change. Responding to mounting pressure, the United States Geographic Board (a successor to the original United States Board on Geographic Names) reversed the decision on July 19, 1911, and the Pittsburgh spelling was restored."

The majority has the capacity to make authorities' rulings irrelevant if they feel strongly enough about it. The IAU certainly has no more force to it than the law changing the name of Pittsburgh. It's not only possible to force the decision to be overturned; it's possible to make it irrelevant whether it's overturned or not.

The Pluto/planet situation is a little more nuanced, because every act of writing "Pittsburgh" tacitly chooses one spelling or another. The real point with Pluto is that there is no scientific reason whatsoever to so label it or not. A scientific paper on Ganymede doesn't need a footnote saying "Ganymede is a satellite of Jupiter." Anyone reading the paper would presumably know that. Likewise with Pluto. If there were a sentence added to a serious research paper asserting which class of object it is, whichever class it mentioned, that sentence would be pure noise to the signal of the rest of the paper.

Posted by: Stephen Aug 12 2008, 08:20 AM

QUOTE (Greg Hullender @ Aug 12 2008, 06:57 AM) *
That's actually a very powerful argument I haven't really heard before -- that the scientific definition of planet should correspond to "worlds that have geology," because that's what Planetary Scientists study.

Hmm. But since dwarf planets and plutoids are NOT planets does this mean "Planetary Scientists" will NOT be studying the geology of Pluto? huh.gif

Presumably that means "dwarf planets" be studied by "dwarf planetary scientists" instead. (Visions of little green geologists peering through telescopes and launching space probes!) laugh.gif

======
Stephen

Posted by: Alan Stern Aug 12 2008, 11:47 AM

QUOTE (Stephen @ Aug 12 2008, 08:20 AM) *
Hmm. But since dwarf planets and plutoids are NOT planets does this mean "Planetary Scientists" will NOT be studying the geology of Pluto? huh.gif

Presumably that means "dwarf planets" be studied by "dwarf planetary scientists" instead. (Visions of little green geologists peering through telescopes and launching space probes!) laugh.gif

======
Stephen



A portion of my point yesterday seems to have been misunderstood, or at least not very well put on my part, so despite being a slow and error prone typist, I'll elaborate a little and hopefully clarify the intended point:

Given there is a field called planetary science and a profession called planetary scientist, I think it is a reasonable (and in fact good thing) for those of us in the field and profession to come to our own consensus on what we mean when we refer to the central objects after which the field and profession are named.

I further think that is up to the practitioners, and rather than practitioners of related fields (read: astronomy, dynamics) to make this determination for ourselves. That a group that was >80% (some would say >90%) non-planetary scientists made a determination in Prague about what they consider to be a good definition of planet is a historical fact. I submit that the numerous technical problems generated by the astronomer's definition of '06 is in fact related to their tangential relationship to planetary science.

I don't wonder that a similarly problematic (disastrous?) and contentious result might obtain if the DPS met to reclassify objects in astronomy like stellar types, galaxies, or GRBs, and then put out declarations to the the press about it.

Now, onward from what I said yesterday, what is truly regrettable, and what I do believe will now change, is that the press and public believe that experts in the relevant subject matter domain made the planet definition determination. They did not. This is in significant measure why so many planetary scientists jumped on the Sykes-Stern petition the week after the 2006 IAU meeting.

-Alan

Posted by: Phil Stooke Aug 12 2008, 02:03 PM

Absolutely right, Alan. The IAU has not really recognized the change in planetary science which occurred in about 1960 with the work of Hackman, Mason and (of course) Gene Shoemaker - the moon and planets became essentially geological objects, and the practitioners in their study mostly geologists, geophysicists, meteorologists and so on. It's like the last gasp of the Urey-Shoemaker dispute, so well told in Don Wilhelms' book 'To a Rocky Moon'.

Of course, this is complicated a bit by an object like Eris, which - at the moment - can only be studied by astronomical means. We have to recognize the broad mix of disciplines involved, and astronomy is part of that. But as you suggest, people who study these objects, from whatever background, should be the ones making the decisions.

Phil

Posted by: Phil Stooke Aug 12 2008, 02:05 PM

JRehling: "And, of course, *anything* that is categorized as "modern" is doomed to be renamed as it fades into the more and more distant past."

Yes indeedy. 'Post-Modern' has now been dropped in favor of 'Pre-Next'.

Phil

Posted by: Ken McLean Aug 12 2008, 02:46 PM

Should we be waiting on further evidence to support planetary accretion such as the Modern Laplacian Theory before deciding what constitutes a planet, ie. born out of solar/stellar system formation? And if so, does that mean we need to class satellites like Titan - which has been postured by some to have formed independently of Saturn's orbit - as a planet? If the orbit of a planet changes does it cease to be a planet, despite being compositionally very similar?

Posted by: Greg Hullender Aug 12 2008, 03:03 PM

QUOTE (volcanopele @ Aug 11 2008, 08:34 PM) *
Don't forget that planetary scientists also study moons, asteroids, comets, dwarf planets, Trans-Neptunian Objects, etc. We don't just study planets wink.gif


You're undermining Alan's argument, you realize. I don't think we can allow you to study comets, unless they're REALLY big comets. :-)

--Greg

Posted by: Juramike Aug 12 2008, 03:12 PM

Objects smaller than the Sun occupy a multidimensional continuum of values. Level of differentiation, atmosphere, size, distance from parent star, crustal materials, past/current geologic processes, etc. Choose the right dimensions, and there will be a unique place for everything: Io, Pluto, Eris - everything could get a coordinate.

All of the objects could be plotted in multidimensional space and subjected to cladistic analysis to draw up clusters of objects. But when you define up the clusters, you may end up drawing up borders that may not make much sense in the big scheme of things. And some of these might end up being arbitrary.

For instance, my own personal level of "interesting objects" [crustally differentiated objects with a solid surface]: Mercury, Venus, Earth, Moon, Mars, Ceres, Io, Europa, Ganymede, Titan, Triton, Pluto.

My list of "preferred interesting objects" [crustally differentiated objects which may have had "recent" geological activity] includes: Venus, Earth, Mars, Io, Europa, Ganymede, Triton, Pluto

And my arbitrary list of "most preferred interesting objects" [crustally differentiated objects which may have had recent geological activity and have an atmosphere and that we've taken pictures of the surface]: Venus, Earth, Mars, Titan

All this demonstrates that the groupings and definitions we give objects are arbitrary in the eye of the definer. (The data itself is not, but how the data is grouped is.)



Pluto will still be Pluto whether we call it a "planet" or not.

Whether Pluto is a "planet" or not, for me, is an uninteresting discussion.

A much more intereseting discussion would try to answer:
How is Pluto similar/different from Earth?
How is Pluto similar/different from Titan?

Those are the questions I get excited about.

-Mike





Posted by: djellison Aug 12 2008, 03:24 PM

FYI - the actual pluto debate itself has been had at UMSF before. It ended with raised tempers, arguments, attacks, people running to teacher to claim they were getting bullied. See the several threads in this sub-forum for further examples.

We're not going down that road again.

Whos job it is to decide, however, is a pertinent and interesting debate. Keep it nice.

Posted by: Alan Stern Aug 12 2008, 03:34 PM

QUOTE (Juramike @ Aug 12 2008, 03:12 PM) *
Objects smaller than the Sun occupy a multidimensional continuum of values. Level of differentiation, atmosphere, size, distance from parent star, crustal materials, past/current geologic processes, etc. Choose the right dimensions, and there will be a unique place for everything: Io, Pluto, Eris - everything could get a coordinate.

All of the objects could be plotted in multidimensional space and subjected to cladistic analysis to draw up clusters of objects. But when you define up the clusters, you may end up drawing up borders that may not make much sense in the big scheme of things. And some of these might end up being arbitrary.

For instance, my own personal level of "interesting objects" [crustally differentiated objects with a solid surface]: Mercury, Venus, Earth, Moon, Mars, Ceres, Io, Europa, Ganymede, Titan, Triton, Pluto.

My list of "preferred interesting objects" [crustally differentiated objects which may have had "recent" geological activity] includes: Venus, Earth, Mars, Io, Europa, Ganymede, Triton, Pluto

And my arbitrary list of "most preferred interesting objects" [crustally differentiated objects which may have had recent geological activity and have an atmosphere and that we've taken pictures of the surface]: Venus, Earth, Mars, Titan

All this demonstrates that the groupings and definitions we give objects are arbitrary in the eye of the definer. (The data itself is not, but how the data is grouped is.)



Pluto will still be Pluto whether we call it a "planet" or not.

Whether Pluto is a "planet" or not, for me, is an uninteresting discussion.

A much more intereseting discussion would try to answer:
How is Pluto similar/different from Earth?
How is Pluto similar/different from Titan?

Those are the questions I get excited about.

-Mike


Mike-

I agree with the high "interest factor" in your two questions just above, start a thread! But regarding planet definition, I hope the the topic (for everyone, not just this forum) needs to move from a "contest" over Pluto (let it fall where it may) to a rational one about planet categorization in general. Putting Pluto in the middle of it clouds the arguments, with people claiming there are issues of sentimentality, American pride, etc.; it distracts attention from the important issue of getting a workable definition and categorization of planets. Sykes and others (not sure about Tyson) have accepted this point and will be echoing it at GPD later this week.

Are you going to be at GDP?

-Alan

Posted by: JRehling Aug 12 2008, 06:52 PM

A title I always find funny is "Lunar and Planetary Science", as though the Moon is the sole non-planet to be discussed in this context. Either it should be called "Lunar and Ganymedian and Mirandan and ... [...] ... and Cometary and Planetary Science" or the lunacy of listing just ONE exception should be discarded immediately. Why would the term be broad enough to include Saturn's rings, but not the Moon?

I think the simple category error here is the presumption that the question "Who decides" is going to end up having an answer. Who decided how Pittsburgh would be spelled? Who decided that the English definite article was "the"? Who decided that when a group is asked to identify itself, the answer that sounds best is "It's us" rather than "It's we"?

The IAU *happened* to come up with a torturous and counterintuitive definition and they *happened* to make a decision that impacts the textbooks and they *happened*, as Alan notes, to consist more of people who study stars rather than solar system objects. However, the idea went sour at the point that the implication was made that a smoke-filled room owned the term "planet", which provides no service to science for objects in our solar system.

Posted by: pumpkinpie Aug 12 2008, 07:06 PM

I've registered to watch the debate but I never got any email confirmation. Am I all set? What do I have to do to watch it?

Posted by: Juramike Aug 12 2008, 07:33 PM

I think the Great Planetary Debate will work itself out over the next several years to decades. And it won't be from a small group in a smoke-filled room, it will be from scientists looking at a much larger dataset (of as-yet undetected and unanalyzed objects) and grouping things according to trends.

A likely example is the historical development of the http://en.wikipedia.org/wiki/Periodic_table. From the initial five elements: earth, wind, fire, water, and lifeforce (see avatar), we now have a clear grouping into 118 (and counting) atomic elements. What is very interesting is that early attempts tried to pigeonhole the elements strictly according to atomic mass (law of octaves). It wasn't until Mendeleev ordered elements according to chemical reactivity with guidance from atomic mass that a clear pattern emerged that allowed elements to be systematically grouped.

[Now, what would've happened if the "inert gas" compound XeF2 [CAS# 13709-36-9] had been known back then? Again, there are always exceptions to definitions.]

Years from now, we'll all look back on this and laugh....then get back to work colonizing Titan.

-Mike

Posted by: Alan Stern Aug 12 2008, 08:13 PM

QUOTE (pumpkinpie @ Aug 12 2008, 07:06 PM) *
I've registered to watch the debate but I never got any email confirmation. Am I all set? What do I have to do to watch it?


Pumpkinpie- I just inquired on your behalf with meeting organizer Hal Weaver. He says you and about 500 of your closest friends who have also registered for the web participation will be getting email info later today answering your particular questions and more.

-Alan

Posted by: laurele Aug 12 2008, 08:50 PM

We may need to come to the realization that no one permanently "decides" such things. Students actually learn more from finding out there are multiple schools of thought driven by different interpretations of the same facts. Maybe some discussions need to be left open for now with caveats that things may change as we learn more. No one is teaching there are X number of exoplanets because it is obvious that we are discovering new ones all the time and that the number and types of exoplanets discovered will inevitably keep changing. It's just a suggestion, but maybe the best way for textbooks and educators to approach the planet question is to point to the Dawn and New Horizons missions, which in only seven years will provide us with a whole new set of data on which to base these decisions. Every time we send a mission to another planet, whether a flyby, orbiter, rover, or lander, we discover new things that no one could have anticipated, such as the water vapor in Mercury's very thin atmosphere.

It's just my opinion, but a reversal of the IAU statement that dwarf planets are not planets at all would go a long way in resolving this issue regarding Ceres, Pluto, Eris, MakeMake, and other round KBOs.

I'm going to be attending the GPD in person, and I look forward to a wonderful, tremendous learning opportunity.

Posted by: tedstryk Aug 12 2008, 09:12 PM

I think a lot of this trouble stems from the questionable process by which the IAU adopted the resolution. Waiting until after most of the delegates had left to bring it up created a lot of bad feelings. Not to mention that the definition passed doesn't really make sense. My fear is that this mess might weaken the IAU's role, something that would create chaos.

Posted by: Greg Hullender Aug 12 2008, 10:07 PM

QUOTE (Alan Stern @ Aug 12 2008, 08:34 AM) *
But regarding planet definition, I hope the the topic (for everyone, not just this forum) needs to move from a "contest" over Pluto (let it fall where it may) to a rational one about planet categorization in general. Putting Pluto in the middle of it . . . distracts attention from the important issue of getting a workable definition and categorization of planets.


It does seem to me that Planetary Scientists are the only ones in a position to do such a thing. If there were a consensus around a really solid definition, I'd expect the other IAU members would defer to it.

Maybe it would help to give a special name to the Magic Eight; call them "Classical Planets" for example. Round, isolated, in circular orbits in the ecliptic -- they certainly SEEM special enough to merit special attention.

Things like the moon or Ganymede could be "Secondary Planets". Again, from a Planetary Science point of view, I don't see how any rational definition can leave them out.

Planets that are part of a belt (like Ceres or Pluto) could stay "Dwarf Planets" but those would now be "planets," not minor planets.

Stuff above the meteorite level could be "subplanets" and we'd just retire the term "minor planet".

Probable planets (e.g. fairly bright KBOs) could be called "planetoids" until we had enough data to class them as dwarf planets or subplanets.

I'm still not ready to consider comets to be any kind of subcategory of planet, but I suppose you could "define" comet as an icy subplanet in a highly elliptical orbit etc.

Kids in school would learn the classical planets. Enterprising ones would learn the secondary and dwarf planets on their own.

--Greg


Posted by: surreyguy Aug 12 2008, 10:10 PM

Maybe I'm just belabouring the obvious here, but while some categorisations (e.g., all bodies whose name begins with 'E') are arbitrary, the good categorisatons are those which reflect theory in some way. That's what distinguishes categories such as '>2000km diameter' from 'roundness'. The thing which I guess I find odd is when people find it hard to switch viewpoint, and thus what categorisation is relevant for the discussion at hand. If you want to discuss tectonic features then the roundness criterion is relevant; if you are talking about the way the architecture of the Solar System has been sculpted over time, then orbital dominance is what you want.

Of course, some definitions may be more useful than others for the purpose of knowing which committee gets to name a body, but you'd think that issue could be settled without people crying 'but what about the children'...

I guess I'm saying that I don't think that there's any such thing as an inherent quality of 'planetness' which we can know - that seems a no brainer, put like that, but a lot of the arguments one sees seem to be predicated on something like it. For example, the use of 'what if we discovered...' scenarios.

Posted by: Alan Stern Aug 12 2008, 10:18 PM

QUOTE (Alan Stern @ Aug 12 2008, 09:13 PM) *
Pumpkinpie- I just inquired on your behalf with meeting organizer Hal Weaver. He says you and about 500 of your closest friends who have also registered for the web participation will be getting email info later today answering your particular questions and more.

-Alan



Now I am told they are getting flooded with extra log in requests for web participation and won't cut off the list until morning. Only then will they send out the instructions, answers to questions, etc.

-Alan

Posted by: Juramike Aug 12 2008, 10:30 PM

QUOTE (Alan Stern @ Aug 12 2008, 10:34 AM) *
Are you going to be at GDP?


I guess I was more interested than I thought. I signed up to get the webcast.
(Hopefully it'll get through my work's firewall.)

Posted by: laurele Aug 12 2008, 10:33 PM

QUOTE (Greg Hullender @ Aug 12 2008, 06:07 PM) *
Kids in school would learn the classical planets. Enterprising ones would learn the secondary and dwarf planets on their own.

--Greg


I like your ideas, but I think kids should be taught the dwarf planets and secondary planets too, not necessarily to memorize, but at least to illustrate that they are an important part of the solar system. Even back in the 70s when I was in elementary school, we learned about the larger moons of the planets. Leaving out Titan, the Galilean moons and the dwarf planets seems to me to be doing a disservice to the kids.

Posted by: tedstryk Aug 12 2008, 10:34 PM

I thing the moon versus planet definition works. Even planet-sized moons have histories so intertwined with their parent planet that it separates them from objects in solar orbit (even Triton was melted down in the process of being captured).

I don't know if this would be a good one for the Planetary Society to get caught up in. The debate is to emotional. The Planetary Society is a non-partisan group (and I am referring to sides in scientific debates, not party politics, although that would also be true I guess), and to risk a result that makes it look petty or turns some of the community against it would be dangerous. Also, it is primarily a group that works to advocate the funding needs of Planetary Science in Congress and to educate the public about planetary science and planetary missions. That even includes educating people about what is being debated. But to step into a debate that some might see as an attempt to supplant the IAU and to risk having a position adopted that alienates some of its constituencies doesn't seem worth it.

Posted by: mcaplinger Aug 12 2008, 10:42 PM

QUOTE (surreyguy @ Aug 12 2008, 02:10 PM) *
...while some categorisations are arbitrary, the good categorisatons are those which reflect theory in some way.

I'm not sure I would use "arbitrary" and "good" as opposites like this. Many (most?) uses of terminology are "arbitrary" but have managed to avoid the emotionalism and controversy that this one has caused.

If it were up to me, I would have just said that everything Pluto-sized and bigger was a planet and everything smaller wasn't, but somehow this has been dismissed as being too "unscientific".

The whole thing reminds me of the vociferous debate I was involved in about whether longitudes should be positive to the east or west (also horribly confused by the IAU.)

Posted by: JRehling Aug 12 2008, 11:46 PM

QUOTE (Greg Hullender @ Aug 12 2008, 03:07 PM) *
Maybe it would help to give a special name to the Magic Eight; call them "Classical Planets" for example. Round, isolated, in circular orbits in the ecliptic -- they certainly SEEM special enough to merit special attention.
[...]
Kids in school would learn the classical planets. Enterprising ones would learn the secondary and dwarf planets on their own.


I don't understand what the motive is to create a term (even a reasonable one) for the purpose of singling out a group. If the purpose is to create a cutoff for educators, perhaps. But scientifically, Mars is still more similar to Pluto than it is to Saturn. Your comments above, especially the ones I've quoted, imply that this isn't about science but about providing direction to educators.

I'll point out that elementary school math teachers neither seek nor find direction in cutting-edge research mathematics, showing just how different those two sides of the topic are. Serious academics in mathematics interact with "quotients" all the time, but they aren't any better than your typical fourth-grade math teacher (who likely has forgotten any calculus they ever knew) to determine the nomenclature in an elementary school text. In fact, the math wonks are possibly especially poorly-suited to do that.

But this puts a pinpoint on the divide between the science issue and the educational issue. And I think the shame of it is that while educators should look to researchers for the basic facts (eg, does Venus have volcanoes?), which is an objective matter, this labeling and nomenclature is not an objective matter, and handing the reins to the researchers to help decide what the kiddies will be taught is just going to make people jaded about what scientists do.

As an aside, I have bought a number of books about the planets for my son, and the subtle misinformation that's rampant in most of them tells me that any possible lesson in classifying bodies correctly (if there were a "correctly") is way below the signal-noise ratio as it is.

(Sample misinformation: Venus's thick clouds MAKE its atmosphere dense.)

Posted by: pumpkinpie Aug 13 2008, 01:08 AM

QUOTE (laurele @ Aug 12 2008, 04:33 PM) *
I like your ideas, but I think kids should be taught the dwarf planets and secondary planets too, not necessarily to memorize, but at least to illustrate that they are an important part of the solar system. Even back in the 70s when I was in elementary school, we learned about the larger moons of the planets. Leaving out Titan, the Galilean moons and the dwarf planets seems to me to be doing a disservice to the kids.


I taught over 16,000 students in a portable planetarium this year. Part of the show was letting the kids choose where in the solar system to visit. Most classes chose to go to Pluto. When I asked what it "is," close to 100% had at least one person who knew it was a dwarf planet. In most classes I heard a chorus of the correct answer.

Knowing its label, of course, isn't enough. That's just a form of memorization, and has no meaning without explanation. I would talk about why its category changed, and that there are bound to be more additions/subtractions/reclassifications as our knowledge of the solar system changes.

Posted by: Greg Hullender Aug 13 2008, 03:49 AM

QUOTE (JRehling @ Aug 12 2008, 03:46 PM) *
Your comments above, especially the ones I've quoted, imply that this isn't about science but about providing direction to educators.

Educators are an interested party, since kids can understand this stuff. Contrast math, where higher math is utterly unintelligible to even a talented undergraduate student -- much less an elementary school kid.

It's not completely frivolous to consider educators. Fascination with the planets is a first step into science for many people.

To recap:

Planetary Scientists (not the Planetary Society!) ought to have first call; this is their field of study, so they have the biggest stake.

The IAU itself needs a criterion for assigning names, and that does need to be based on what can be observed -- not what properties might be observed if only we could send a probe.

But educators inspire the next generation -- both the young scientists and the interested non-scientists who are happy to see their tax dollars spent exploring space. Their needs cannot drive the definition, but any definition certainly needs to take them into account.

--Greg

Posted by: Greg Hullender Aug 13 2008, 04:01 AM

QUOTE (pumpkinpie @ Aug 12 2008, 05:08 PM) *
I taught over 16,000 students in a portable planetarium this year. Part of the show was letting the kids choose where in the solar system to visit. Most classes chose to go to Pluto.


Yep, kids like superlatives. I felt that way as a kid too. It's hard to beat "furthest away," although I wonder if Jupiter came in second? (Actually I'd guess Saturn, since the rings are unique.) If they knew about Sedna, they might have picked that.

Pleasing the kids isn't the same as educating them, though. All kids know this already. :-)

--Greg


Posted by: nprev Aug 13 2008, 04:14 AM

QUOTE (Greg Hullender @ Aug 12 2008, 07:49 PM) *
It's not completely frivolous to consider educators. Fascination with the planets is a first step into science for many people.


That's an excellent point on several levels; certainly I was first interested in science by the very concept of planets.

I hope that some educators will participate in the GPD. They may bring some perspective to the whole issue by defining concepts that really communicate with people (and, hopefully, not trying to sell a particular viewpoint.) SInce IMHO the whole thing is quite subjective, it might be much more important to make the final result intelligible & teachable.

Posted by: JRehling Aug 13 2008, 04:50 AM

QUOTE (pumpkinpie @ Aug 12 2008, 06:08 PM) *
I taught over 16,000 students in a portable planetarium this year. Part of the show was letting the kids choose where in the solar system to visit. Most classes chose to go to Pluto. When I asked what it "is," close to 100% had at least one person who knew it was a dwarf planet. In most classes I heard a chorus of the correct answer.

Knowing its label, of course, isn't enough. That's just a form of memorization, and has no meaning without explanation. I would talk about why its category changed, and that there are bound to be more additions/subtractions/reclassifications as our knowledge of the solar system changes.


I would dispute that it is the "correct" answer any more than the law made "Pittsburg" the correct spelling of that city's name.

Age and background are important variables, but I think this Planet Debate -- not just the particular IAU decision, but the debate itself, as it's been transmitted -- is an absolute disaster for primary education. Speaking as a parent who's bought a few books for his son, some of which were updated with impressive speed. For very young kids, the meta-arguments about classification systems are completely incomprehensible. And I have books where the page devoted to Pluto is now half about this issue. This is a shame first because it displaces whatever else could have been said in that half-page. Second, because kids below a certain threshold of grasping abstractions totally miss whatever point could be made beautifully to a student of the philosophy of science. It's like taking an elementary school text about a tropical island with imagery and comments about the weather and diet and replacing them with information about how the local legislature works. For kids who are sufficiently below the level of understanding for that, it doesn't even provide the building blocks of understanding -- it's just 50 seconds of noise, the way a literature lecture in Hungarian would fail to educate a mature English speaker of one iota of the subject matter or Hungarian.

This subject matter near and dear to our hearts gets a limited amount of discussion in the classroom, and this issue only serves to crowd out some of the real content to replace it with opinion presented as fact. With a tinge of pedantry to boot. That's no wins and three losses.

Posted by: JRehling Aug 13 2008, 05:04 AM

QUOTE (Greg Hullender @ Aug 12 2008, 08:49 PM) *
Educators are an interested party, since kids can understand this stuff. Contrast math, where higher math is utterly unintelligible to even a talented undergraduate student -- much less an elementary school kid.

It's not completely frivolous to consider educators. Fascination with the planets is a first step into science for many people.

To recap:

Planetary Scientists (not the Planetary Society!) ought to have first call; this is their field of study, so they have the biggest stake.

The IAU itself needs a criterion for assigning names, and that does need to be based on what can be observed -- not what properties might be observed if only we could send a probe.

But educators inspire the next generation -- both the young scientists and the interested non-scientists who are happy to see their tax dollars spent exploring space. Their needs cannot drive the definition, but any definition certainly needs to take them into account.


But kids cannot understand the comparative pros and cons of alternative classification systems. Not before about ninth or tenth grade, on average. Younger than that, and a discussion like that will just be noise. And if instead you just give them the IAU definition as fiat, you're passing opinion off as science.

No, it certainly is not frivolous to consider educators. I'd go much further -- this issue is primarily of interest to educators, and has done them the disservice of asking them to accept an arbitrary and divisive definition with the misinformation that it is a scientific truth newly had.

"This" is not Planetary Scientists field of study. As I mentioned before, the class of body that Pluto might be does not inform scientific papers on Pluto, just as papers about Mars do not hinge on Mars being a planet. Research scientists have no stake in this, but have chosen to browbeat educators into accepting a fiat which is not science, shaky classification, and poor education. And this would be equally true if they had (or "will", as they likely will, in time) handed down a definition ruling Pluto to be a planet.

Just to take an arbitrary example of the non-usefulness of this term for scientists, here's a poster/paper about the spectra of Pluto and Charon: http://www.lpi.usra.edu/meetings/acm2008/pdf/8150.pdf

The paper doesn't anywhere use the terms "planet" or "dwarf planet", or any terms for Charon, for that matter. Can we conceive of any way in which such terms could better inform the science, if they were included in this paper? For any proposed definition of "planet"? I sure can't think of one.

In essence, the term has no use for scientists. It has a folk use, like "hill" and "river", and is therefore useful in folk senses, in the classroom. For scientists to call this their field and therefore their term is like the legislature saying that city names are their field and therefore theirs to decide. So it began in Pittsburg and so it ended in Pittsburgh.

Posted by: Greg Hullender Aug 13 2008, 05:18 AM

QUOTE (JRehling @ Aug 12 2008, 10:04 PM) *
In essence, the term has no use for scientists. It has a folk use, like "hill" and "river", and is therefore useful in folk senses, in the classroom. For scientists to call this their field and therefore their term is like the legislature saying that city names are their field and therefore theirs to decide. So it began in Pittsburg and so it ended in Pittsburgh.


It is this argument that I have been most bothered by -- it seems incredibly anti-science to me. But only a planetary scientist can answer it with any authority.

Your Pittsburgh example is poor by the way, since (the way I heard the story) it's the only US city that resisted standardization.

--Greg



Posted by: JRehling Aug 13 2008, 06:24 AM

QUOTE (Greg Hullender @ Aug 12 2008, 10:18 PM) *
It is this argument that I have been most bothered by -- it seems incredibly anti-science to me. But only a planetary scientist can answer it with any authority.


That statement baffles me. Axiomatic trust in authority? Scientists have the answers because they are scientists?

In a software company, it's frequently evident that the engineers are not the best people to name things. Just because astronomy is not-for-profit doesn't change that. The engineers know the software best, spending their days hands-deep in it. That does not make them the best ones to lay down the nomenclature, either for internal or external purposes. It's quite a separate thing from the subject matter expertise.

While I would expect to trust scientists first in a scientific matter, this is a nonscientific matter which happens to be attached to objects that science studies. And while one might expect them to have uses for terms they use in their work, I cited the brief paper/abstract on Pluto to show that the term is not essential to science, and I would certainly welcome an example where the term "planet" was helpful to any scientific paper on any solar system object. If it's about Mars, it's about Mars.

And Pittsburgh is not a poor example because it's the only example of a place that resisted the fiat. One, because it's only the largest of several places. (Pittsburgh, KS; Edinburgh, Indiana; Plattsburgh, NY; Newburgh, NY; Newburgh, IN). Two, because the point is that public usage is a force to be reckoned with. If there were no local affection for a particular spelling elsewhere, then it was a one-sided tug-of-war that the authorities won by default. In Pittsburgh, the two went head to head and the authorities lost.

Posted by: alan Aug 13 2008, 07:22 AM

It's too bad the debate tends to fixate on Pluto and whether the dwarf planets should be considered planets. I think the techniques used to decide which of the TNO's are dwarf planets is more interesting. For example, determining how large an object needs to be before it is in hydrostatic equilibrium, and the methods used to estimate the diameters of the objects.

I've seen some claims that an icy body would be in hydrostatic equilibrium if it is over 450 km in diameter. But I've also seen a presentation (IIRC by Tancredi) that used the shape of light curves and some models to estimate the density and roughness of objects which found a couple of objects to be either to rough or not dense enough to be in hydrostatic equilibrium. Some of those objects have been estimated using infrared radiation detected by the Spitzer Space Telescope to be 600-700 km in diameter. It looks like these estimation methods will need to be verified by other methods such as determining the size and shape by observing stars being occulted by the objects.

Posted by: djellison Aug 13 2008, 07:44 AM

QUOTE (JRehling @ Aug 13 2008, 07:24 AM) *
Scientists have the answers because they are scientists?


Biologists classify animals (a cow is still a cow no matter what genus it's in).
Paeleontologicists classify fossils (T-Rex is T-Rex regardless of who you consider its cousins to be).
Librarians classify books (Roving Mars is still Roving Mars if you put it in the science section or the biography section).

Planetary Scientists should classify planets.

Posted by: surreyguy Aug 13 2008, 10:05 AM

QUOTE (djellison @ Aug 13 2008, 08:44 AM) *
Planetary Scientists should classify planets.


You'd think that would be a no-brainer, wouldn't you?

The only caution I'd have is to avoid circularity (!): you define planetary scientists as people who study planets, and then this group defines planets. For example, I would think people would count the study of asteroids and comets under planetary science (though I'd be interested to hear if people think otherwise), and you don't want to end up with a situation where yet more people feel excluded by the outcome of a definitional debate.

That said, the representation at GPD seems encouragingly broad.

Conversely, educators should decide how they will convey the science to the public (and, yes, there will be educators at GPD too - go look at the abstracts), with input, not legislation, from the scientists. I'm surprised more hasn't been made of the idea of a technical definition - for example, a strawberry is not technically a berry, and a shark is not technically a fish, and scientists and the public both seem to live happily with that.

Posted by: djellison Aug 13 2008, 10:32 AM

QUOTE (surreyguy @ Aug 13 2008, 11:05 AM) *
you define planetary scientists as people who study planets, and then this group defines planets.


At that point, we enter the realm of utterly pointless semantics. We all know what planetary scientists are. They study the 'things' out there. Earth, Mars, Titan, Pluto etc etc.... the bodies pertinent to the issue in hand. Thus they should be classifying them.

People who study quasars, nebulae, cataclismic variables and so on are not and were not the right body for that.

Posted by: Stephen Aug 13 2008, 11:39 AM

QUOTE (djellison @ Aug 13 2008, 05:44 PM) *
Planetary Scientists should classify planets.

This is starting to sound like a potential turf war; and like all turf wars it generally all comes down to where you draw the line...and who is entitled to exercise the power to draw those lines.

So "Planetary Scientists should classify planets", eh?

OK, but who gets to decide what is a planet and what isn't (so as to allow planetary scientists to get on with their all-important classification work)? Planetary scientists themselves?

That is to say, do planetary scientists ALONE get to decide not just what a planet is but where the line is between (say) planets and stars. (Eg is a brown dwarf a star or is it a planet?)

On the other hand those who prefer to classify stars (let's call them "starry scientists", "star scientists" for short; after all if you can have "PLANETary scientists"... smile.gif ) might like to have some kind of a say of their own in that sort of decision. That would, however, raise the question of just how much of say they would be entitled to. Are they only entitled to a say on drawing the line between stars and planets and would then be turfed out of the meeting room when the discussion turned to the line between (say) planets and comets? (Instead the "cometary scientists" would be allowed in and given a say. smile.gif )

Of course the very line implied above between "planetary scientists", "star scientists", and "cometary scientists"--not to mention "moon scientists", "cometary scientists", and "plutoidary scientists" (let's try to be consistent here! rolleyes.gif )--raises the issue of just who exactly is a "planetary scientist" anyway?

Higher up this thread somebody (volcanopele) pointed out: "Don't forget that planetary scientists also study moons, asteroids, comets, dwarf planets, Trans-Neptunian Objects, etc. We don't just study planets." That statement could be construed to suggest that a geologist is basically nothing more than a "planetary scientist" who specialises in a single planet: Earth! (And something similar might be said of, "moon science", 'cometary science" etc. ) Or to phrase the matter another way, "planetary science" might be said to be not a branch of geology. Geology (aka "Earth science") is actually a branch of "planetary science"!

On the other hand, is "planetary science" the study of any planet EXCEPT Earth? If so, that would seem to exclude GEOlogists per se from having a say in deciding what exactly is a planet. rolleyes.gif

======
Stephen

Posted by: Juramike Aug 13 2008, 11:50 AM

QUOTE (surreyguy @ Aug 13 2008, 05:05 AM) *
a strawberry is not technically a berry, and a shark is not technically a fish...


...and a cow with 50% mouse genome is technically no longer a cow(wt) [wt = wild type].



How about we let the term "planet" have the widest possible use? Let everything go in there.

(OK, make a cut somewhere: like "objects composed of normal-generacy atoms at a density > interstellar gas nebula that are not currently undergoing fusion")

That will allow "planetary" scientists to study gas giants, comets, ice giants, moons, rocks, KBO's, etc.
Each paper will need to define the set of comparitive objects de novo: "We compare Pluto with other KBO planets [Sedna, Eris, Makemake,...]"

And educators will have to introduce students to the full wonderful diversity of objects in and beyond our solar system.


Eventually, better definitions will arrive, most likely from the same set of comparitive objects being used in the scientific literature. (Just like the chemical reactivity patterns eventually helped define the Periodic Table).

-Mike

Posted by: djellison Aug 13 2008, 12:29 PM

QUOTE (Stephen @ Aug 13 2008, 12:39 PM) *
rolleyes.gif


Quite.

Posted by: Ken McLean Aug 13 2008, 02:19 PM

Why don't we just accept the geo- prefix as its proper meaning of ground/earth (as opposed to Earth) and call it all geoscience?

Posted by: JRehling Aug 13 2008, 05:53 PM

QUOTE (djellison @ Aug 13 2008, 12:44 AM) *
Biologists classify animals (a cow is still a cow no matter what genus it's in).
Paeleontologicists classify fossils (T-Rex is T-Rex regardless of who you consider its cousins to be).
Librarians classify books (Roving Mars is still Roving Mars if you put it in the science section or the biography section).

Planetary Scientists should classify planets.


"Biologists classify animals" is a good one to look at. First of all, they do so with controversy and alternate approaches of many kinds.
I think George Lakoff laid out a pretty good look at this and how biologists really aren't very good at stepping back and considering the meta-issues of classification, peerless as though their knowledge may be of the DNA and the organs and so on. He has a very good analysis of some of the controversy which I think is very relevant to the planet debate, but is also way too long to copy-paste here.

But I think it's a useful case to look at because there are some similarities, and the biology controversy surrounding the kingdoms is several years further along. And also has relevance for kiddies' textbooks.

One there were two kingdoms in biology: plant and animal. Then three. Then two "empires". Then 4 kingdoms, followed by 5 and by 6. Then three domains. Some of these various systems were refinements of some other, compatible. Sometimes they were incompatible and led to division, name-calling, hair-pulling, etc. We can't rehash all of the drama.

But step back and consider the relationship of this to the children's schoolbooks. At which points in the debate do you shred the previous edition, buy a new one and teach the new classification system as fact? Keep in mind that we're talking about 12 years on average between a new system. And each new system is proposed but not accepted with unanimity. The idea that any of this strikes anyone as a matter of fact is as incomprehensible as someone saying that the child who said that Pluto was a dwarf planet is "correct".

This is all very good stuff for students of the history and philosophy of science -- wonderful tangles of complexity and controversy and elusive truth. But it's horrible subject matter for children 9 years old. They just don't get it. Can't. And lots of the PhDs don't get it either, as Lakoff describes. They get one system or another and live by it as a religion, but they can't see the interrelation of the alternate systems that their colleagues favor.

In some cases, though, there is an important basis in the biological classification of kingdoms. Some tiny critter's genetic tree might depend crucially on some phenotype or genotype. It's controversial, but worth pursuing. There is reason to believe in a light at the end of the tunnel.

For planetary science, the term "planet" isn't even useful -- or I'd like someone to point out how it is useful in discriminating the kinds of bodies we're talking about. A paper on Pluto's spectrum cannot possibly be informed by whether or not the thing cleared its orbit. The definition they've latched onto has nothing to do with what they study.

So the harm in all of this is to take a vote of disputed authority, and promptly rewrite the textbooks and tell the kiddies that we've learned something through science, when science had nothing to do with it. And keep an eye on your watch, because the Whittaker system of biological kingdoms had 8 years before the next one came along, which is even less time than Pittsburgh lost its "h".

Posted by: stevesliva Aug 13 2008, 06:52 PM

Three (or more) issues here:

1. The IAU definition sucks.
2. The IAU lacked authority.
3. 'Planet' could end up being as imprecise a term as 'continent' or as precise a term as 'metal.'

You go in an infinite loop from #3 back to #1 because of the whole "cleared its neighborhood" crapola. So a planet is the biggest thing around? Right, like lakes are bigger than the biggest ponds around. Mountains are bigger than the biggest hills around.

A lot of people are either bothered or not bothered by number 3. With some terminology that predated science, like the word 'metal,' we have been blessed with some rather precise terms. This is generally because they had specific, quantized characteristics, and not relative characteristics. Metals were defined as ductile, shiny, malleable, whatever. They were not defined as less shiny than diamonds and more shiny than rocks. Turns out there is conductivity, electrons, etc, but what is a metal and what is not has been relatively constant.

On the other hand, 'Continent' has somehow not seen obsolescence due to science discovering plate tectonics, even though we now know there is a fault above India and not one between Europe and Asia. So Europe isn't really a continent, and India is??? Try to read wikipedia for a precise definition of 'continent.' It's all about "convention." Try telling every grade school teacher that we now have the continents of Eurasia and India. In my opinion, either way would be fine, but you are just redefining an admittedly imprecise term. The maps of the world on wikipedia's plate tectonics article and wikipedia's continent article do not match. Science doesn't match the pre-existing term, yet it will still adopt it when discussing "supercontinents" and the like. Schools still teach students the continents, even though it's not a precise term.

You can count me as not bothered by #3-- I'd take it either way-- precise, or defined "by convention." But I certainly understand the disgust with the IAU's botched attempt at "precise."

Posted by: surreyguy Aug 13 2008, 06:56 PM

To me the significant point about the biological analogy is that there is not a unique classification system. Classifications as 'top predator', 'predator', etc., or aerial, marine, littoral, etc. are just as valid as the phylogenetic one depending on the kind of investigation one undertakes. But they can be completely cross-cutting. It's easy to kid oneself that the phylogenetic classification is somehow 'real' or at least trumps the others, and that there might be something similar for bodies 'out there'. I don't think it is, and I don't think there is.

Posted by: Floyd Aug 13 2008, 07:08 PM

QUOTE (JRehling @ Aug 13 2008, 01:53 PM) *
"Biologists classify animals" is a good one to look at. First of all, they do so with controversy and alternate approaches of many kinds.


A few comments from a microbiologist:
I think there is some confusion between scientific research and authority to define scientific terms.
Progress in science results from experiments where data is generated and analyzed. Hard science deals with measurements and validating hypotheses. However, every field need a vocabulary to communicate within the speciality and to the broader community. The assigning of objects (molecules, bacteria, planets) to groupings has more to do with esthetics than science (but should be scientifically informed). Determining the mass of a virus or planet is a scientific task which we can do with great precision. Coming up with definitions or names depends on building consensus (no standard error bars) among scientists in the field.
In biology, we can determine the evolutionary distance between living organisms by sequencing the DNA for the small ribosomal RNA and counting the mismatches in the aligned sequences. This measurable information is helping to define the grouping of all living organisms (Kingdom, Phylum, Order ...Genus, Species). In microbiology, an international committee validates all names, but microbiologists are free to ignore approved names for what they think is correct. Usage and consensus eventually rule. The scientists responsible for naming grouping and objects in biology do so only for their area of expertise. Zoologists name animals, Botanist name plants and microbiologist name bacteria and archaea. Seems logical to me for planetary scientist to come up with the definition of a planet. Its helpful if the scientific definition does not differ too much from common understanding or general usage (but often it does for good reason).
The IAU definition seem to flunk the esthetics test as well as the consensus of people in the field test.
-Floyd

Posted by: JRehling Aug 13 2008, 08:04 PM

All of these examples are useful for setting up a classification of Classifications.

"Continent" has three useful candidate definitions.

1) The large, nearly-contiguous landmasses evident on globes. Ignoring the isthmi (there's a word you hadn't seen yet this decade) of Suez and Panama, you have North America, South America, Australia, Africa, Antarctica, and Eurasia. If you're a traveler -- an extreme mountaineer, perhaps -- it's quite useful. Or for setting up international fishing domains or somesuch.

2) The landmasses known to the ancients, augmented with the four discovered later. Same as above, but with Europe and Asia separated.

3) The landmasses whose tectonic plates whose areas are centrally or primarily land instead of sea. That puts India and Arabia on the list, with Eurasia grouping Europe and Asia.

One thing I find obnoxious about the whole planet thing is the presumption that because the people using #3 are scientists that their definition is "The" definition, leaving the PhDs to "tut tut" and stroke their beards kindly in derision, and leaving museum docents to tell the child who "knows" about #3 that he/she is correct and leaving the poor, misinformed kids brought up on literature and culture to sulk in their incorrectness. It's so wrong. It's not only factually wrong; it's immoral.

No one should begrudge geologists the use of #3. It's great for what they're doing. It's useful. It's a happy world where they use it for their purposes without feeling like silly Virgil and the whole Classics department are ignorant because they use #2 and brow-beating the elementary schools of the world into adopting #3 because it's a fact. Although it's great if geology teaches that #3 is useful -- for geology.

Now if scientists had stumbled upon a scientifically useful definition of planet and kept it to the scientific domain without sending out a memo that the silly people are incorrect and ignorant, that would have been fine. But what has happened has deviated from that in three unfortunate ways:

1) The memo has been sent out. Kids who use that definition are told they're correct. Kids who don't aren't.
2) The definition was almost painstakingly crafted to be useless to scientists! Far worse than if geologists had brow-beaten the geographers into submission, this is a case where the scientists have created a definition that ONLY has relevance on the other side of the boundary. The scientists themselves have no use for it.
3) Per my observation of the books I have (unfortunately) bought and taken into my own house, actual scientific content that was present in earlier editions has been eliminated and replaced with this fad. Whatever meager information was once there about Pluto, it's now been cut in half. Instead of telling them that we can use the light from Pluto to tell that it's made of ice, we're telling them something that isn't science.

Posted by: Greg Hullender Aug 13 2008, 08:16 PM

QUOTE (Stephen @ Aug 13 2008, 03:39 AM) *
That is to say, do planetary scientists ALONE get to decide not just what a planet is but where the line is between (say) planets and stars. (Eg is a brown dwarf a star or is it a planet?)


I think the point is that everyone already knows what it is that Planetary Scientists study. That's not at issue, even a little bit, and with that the rest of your argument collapses.

As for the arguments that others keep making that Planetary Scientists themselves have no use for the term, let me quote Alan Stern from earlier in the thread:

QUOTE (Alan Stern @ Aug 11 2008, 11:16 AM) *
Since planetary science is a field and planetary scientists have a profession, I do not think we can or want to retire the term which planets. Instead, our field and our profession need to come to a consensus on what we, the practitioners, consider to be planets vs. smaller and vs. larger things.


Note that this is the quote that changed my mind.

I also thought of another group who might appreciate a good definition of planet as well as a selection of subcategories. Those would be the scientists who are doing simulations of solar system formation. It could be useful for them to have a better vocabulary to describe what sort of bodies their simulations are generating. I suspect those guys are already Planetary Scientists of some stripe or another, but I'm not sure. Theirs would certainly be a useful voice in the debate, I'd think.

--Greg

Posted by: JRehling Aug 13 2008, 08:34 PM

Per the term "planetary", it's clear that the field is concerned with things that aren't planets. I believe we can rightly say that some biologists are concerned with things that aren't alive, but that relate to life. Both on macroscopic scales and microscopic. And Saturn's rings aren't even in the ballpark of being anything someone would call a planet. But I don't see why that calls for a definition of planet. A biologist doesn't need a formal definition of "life" before studying proteins. I don't even see why a definition of "life" would be useful before, during, or after someone starts a study of proteins.

The current IAU definition of "planet" does seem to be to have some possible use for dynamicists. As Greg posited, for discussion simulations of planetary system evolution and so on. Although exactly which terms they'd find useful (and why they would want to steal the term "planet" instead of something like "accretion nucleus"), we'd need a dynamicist to say. But I think it would be just as inappropriate to have someone like that create a definition that impinges on elementary school textbooks as it would someone who studies the surface and interior processes of such worlds.


Posted by: Greg Hullender Aug 13 2008, 08:34 PM

QUOTE (JRehling @ Aug 13 2008, 12:04 PM) *
One thing I find obnoxious about the whole planet thing is the presumption that because the people using #3 are scientists that their definition is "The" definition, leaving the PhDs to "tut tut" and stroke their beards kindly in derision, and leaving museum docents to tell the child who "knows" about #3 that he/she is correct and leaving the poor, misinformed kids brought up on literature and culture to sulk in their incorrectness. It's so wrong. It's not only factually wrong; it's immoral.


I don't see this, though. There are countless popular terms that don't match the scientific ones, and it doesn't bother anyone. An architect friend once told me that what I call "asphalt" he calls "asphaltic cement," and that for builders, asphalt is just one of the ingredients. Matters a lot if you're a builder, but the general public doesn't care. It's cute to know that a tomato is technically a fruit, not a vegetable, but only a botanist cares. Kids learn about it, but they don't go correcting their parents about it.

Or consider a rock that falls from space. In space, it's a "meteroid" (and presumably an object a Planetary Scientist might want to study), but once it hits the atmosphere, it becomes a "meteor" (perhaps of interest to Meterorologists) :-) and when it hits the ground, it's a meterorite (and belongs to Geology). Normal folks don't know these distinctions (if I've even got them right myself) and they don't care. They just call everything a meteor. A bright kid might correct his elders in a museum -- "That's not a meteor, dad; it's a meteorite!" -- but they just chuckle.

I can't for a minute see how any of this rises to the level of a moral issue. And kids "brought up on literature and culture" simply say "who cares?" They never give the wrong answer in the first place.

--Greg

Posted by: surreyguy Aug 13 2008, 08:50 PM

Yay! Registration came through. And... you can submit questions... Bwahahaha!

Posted by: Greg Hullender Aug 13 2008, 08:51 PM

In other news, I got my "Instructions for Viewing The Great Planet Debate Webcast" e-mail about an hour ago. So it's tomorrow, starting at 1:30 PM PDT (2030 UT).

--Greg

Posted by: JRehling Aug 13 2008, 09:05 PM

QUOTE (Greg Hullender @ Aug 13 2008, 01:34 PM) *
I can't for a minute see how any of this rises to the level of a moral issue. And kids "brought up on literature and culture" simply say "who cares?" They never give the wrong answer in the first place.


If there is a room full of kids who are offering answers, and after one of them gives the "asphaltic cement" answer and the docent says "Yes -- correct!", the kids who gave other answers before that, without getting the positive feedback, certainly notice.

And my ideals for education are not a one-child = one-subject delineation where the literature/culture kids have to feel like they're on enemy turf in the science museum, where the science-kid gets his "Yes -- correct!"s for a day. If it's because the science kids actually DOES know a fact (like the Sun being bigger than the planets), then that's great. If it's because of a matter of interpretation that someone's going to pretend is a fact, eg, a geologist saying the geographical definition is wrong, then it's a problem.

If a kid who'd been told that Europe was a continent interacted with someone preaching that the tectonic plates determine the continents, telling the kid that he/she is not correct is not appropriate.

And portraying a vote that went one way as an advance in knowledge and a determination of what's correct is also not appropriate. If it were correct in the conventional sense, this debate wouldn't be taking place.

Posted by: djellison Aug 13 2008, 09:07 PM

QUOTE (surreyguy @ Aug 13 2008, 09:50 PM) *
Yay! Registration came through. And... you can submit questions... Bwahahaha!


Not got mine yet.

Posted by: Floyd Aug 13 2008, 11:20 PM

JRehling It is clear that you don't like the IAU telling everyone (public, educators) that their definition is a new "Scientific truth". I think most people on this forum would agree. Its just a definition which is neither true or false, but rather useful or not or esthetic or not—most would agree that IAU's definition is not great, or we would not be having this discussion. However, at times you seem to imply that arrogant scientists are to blame for confusing the public. I don't think this is the case. I think we should allow the possibility of a disconnect of the general definition of a word from the definition most useful to a scientific discipline. Do you agree that scientist should be free to give very specific definition of words for their specialty as long as they don't put out press releases stating that a simple definition is a "TRUTH". I sort of like the very old definition of a planet as anything that wonders relative the distant stars. Children and the public should be made aware of the fact that there are often multiple definitions--I agree that "right answeres" should generally have more qualifications.
Floyd

Posted by: JRehling Aug 13 2008, 11:58 PM

I'd be happy if this were a situation where a term had a scientific use and a folk use, and never the two did meet. A wonderful example of that is "work", which has a definition in physics and a definition in ordinary life which is quite different. (Except when a laborer hauls things up a hill, and activity which meets both definitions.) Hopefully, no one was ever lectured that their job wasn't work because it failed to meet the physics definition.

However, this "planet" definition has no apparent scientific use, and is being used to *replace* the way the term was previously used. So it's a total strike-out. It doesn't help science, and it does impact the folk audience (kids, laypeople).

And while I agree that a very astute audience (graduate students in the history and philosophy of science) could really sink their teeth into these distinctions, the books I've bought for my son are aimed at an audience that is struggling to understand how a space rock could create a hole in the surface of a planet. Meta-classification is way too abstruse a subject for them. So the discussion doesn't enrich their education. It replaces a small part of it with static. The same way that replacing a small portion of a kid's book about a small country with a paragraph about their bicameral legislature would be static.

Posted by: Stephen Aug 14 2008, 02:08 AM

QUOTE (stevesliva @ Aug 14 2008, 04:52 AM) *
3. 'Planet' could end up being as imprecise a term as 'continent' or as precise a term as 'metal.'

Actually, what constitutes a "metal" to a geologist (or an engineer) is quite different to what an astronomer means by that word! laugh.gif

Which, of course, raises the question of what would happen if the geologists' union decided that they had the right to determine the meaning of the word "metal"? Would astronomers thereafter follow the new "official" definition or would they blithely ignore the dictates of the geologists and continue to use their own idiosyncratic version of the word (namely, that every element but hydrogen and helium is a "metal")?

======
Stephen

Posted by: laurele Aug 14 2008, 03:28 AM

QUOTE (Greg Hullender @ Aug 13 2008, 03:34 PM) *
I can't for a minute see how any of this rises to the level of a moral issue. And kids "brought up on literature and culture" simply say "who cares?" They never give the wrong answer in the first place.

--Greg


Some kids might get so confused by all of this that they just decide it's not worth learning and give up on the subject altogether. When thinking of education, we need to focus on how to excite kids about astronomy rather than turn them off to it.

Also, regarding the IAU requirement that an object clear its orbit: wouldn't that preclude any binary planetary systems since two planets orbiting one another would not be considered to have "cleared their orbits"?

Posted by: Greg Hullender Aug 14 2008, 03:38 AM

QUOTE (JRehling @ Aug 13 2008, 03:58 PM) *
However, this "planet" definition has no apparent scientific use, and is being used to *replace* the way the term was previously used. So it's a total strike-out. It doesn't help science, and it does impact the folk audience (kids, laypeople).


1) Actually, I think your argument is that any planet definition is useless, and we've already established that this claim is false. I don't know why you keep repeating it. At this point, you need to get a bona fide Planetary Scientist to make that claim, and I don't think you can find one. Failing that, you should drop it.

2) It does occur to me that a word like "planet" is very different from words like "fruit" or "work" in that the general public has no independent experience with planets, so the scientific definition has to be the only definition. Contrast fruit, where the common definition requires it to be sweet (thus excluding the tomato) or work, where the popular and scientific terms only vaguely match. No one is bothered by this conflict, and scientists are free to redefine either term without much notice from the public.

But for "planet" the only defiinition that matters is the scientific one. The public cannot create its own term, since it has no use for it. Some special term for the eight planets the public can actually see with (at most) binoculars probably makes sense, but even that's weak; almost no one is looking.

Planetary Scientists should define to term to suit themselves, and everyone else should accept their definition. They should give some guidance to educators, perhaps along the lines I've suggested, but that's it. It's just not anyone else's business. (Clearly I have drunk Alan's Kool-Aide to the lees.) :-)

3) It does seem clear that the IAU overstepped. Their real message seems to be that they don't want any more "planets," but their actions sinice suggest they're reserving the "cool" names for bodies large enough to be round. That being the case, since their whole role is assigning names, they're unaffected by any serious proposed definition anyway. I'd argue that removes them as a party with a legitimate interest.

--Greg

Posted by: Greg Hullender Aug 14 2008, 03:46 AM

QUOTE (laurele @ Aug 13 2008, 07:28 PM) *
Some kids might get so confused by all of this that they just decide it's not worth learning and give up on the subject altogether. When thinking of education, we need to focus on how to excite kids about astronomy rather than turn them off to it.

Also, regarding the IAU requirement that an object clear its orbit: wouldn't that preclude any binary planetary systems since two planets orbiting one another would not be considered to have "cleared their orbits"?


Well, for it to rise to a "moral issue," I really think it needs to be so bad that it makes the kids kill their teachers (or vice versa), and I don't think we've seen that yet. :-)

As for the "cleared its orbit" definition, I think I see how that can be cleaned up, but I now think that's the wrong way to go.

--Greg

Posted by: dvandorn Aug 14 2008, 04:29 AM

Do also remember that whatever definition of planet upon which we achieve consensus doesn't only need to account for solar system objects. Such a definition ought also to include bodies orbiting other stars.

I can conceive of a lot of solar systems in which major planets have not (yet) cleared their orbital neighborhoods. Young systems, for example, where accretion is *nearly* finished, or older systems where large planets are migrating closer to, or farther away from, their stars. Or systems in which a hot mega-Jupiter, orbiting its star in two or three days, finally spirals in and hits the Roche limit.

Are all of the bodies in such systems not planets because of these circumstances? Does "planet" only and forever describe only eight bodies in orbit around our Sun, disregarding bodies that are already described as "extrasolar planets"?

Or do we need to get better data on other systems to find out just how many adjustments we need to make to *any* definition of planet based only on our experience of our own solar system?

-the other Doug

Posted by: Stephen Aug 14 2008, 04:40 AM

QUOTE (Greg Hullender @ Aug 14 2008, 01:38 PM) *
2) It does occur to me that a word like "planet" is very different from words like "fruit" or "work" in that the general public has no independent experience with planets, so the scientific definition has to be the only definition. ... [F]or "planet" the only defiinition that matters is the scientific one. The public cannot create its own term, since it has no use for it. Some special term for the eight planets the public can actually see with (at most) binoculars probably makes sense, but even that's weak; almost no one is looking.

FYI the word "planet" (which derives from the Ancient Greek for "wanderer"), and the concept behind it, is a very ancient one. It existed long before science was even thought of, and thus long before the true nature of planets was discovered.

In other words, it was the public not the scientists who first noticed the wandering stars in the heavens and who created both the word and the concept behind it for those "stars". Astronomers and other scientists are merely the johnny-come-latelies who are now making the most use of it!

Why then should it be the scientists alone who now decide what that word means? That would look an awful lot like expropriation, IMHO. That is to say, science would have presumptively taken custody of a public word and decided to dictate to that public what that word should mean.

======
Stephen

Posted by: JRehling Aug 14 2008, 05:05 AM

QUOTE (Greg Hullender @ Aug 13 2008, 08:38 PM) *
1) Actually, I think your argument is that any planet definition is useless, and we've already established that this claim is false. I don't know why you keep repeating it. At this point, you need to get a bona fide Planetary Scientist to make that claim, and I don't think you can find one. Failing that, you should drop it.

2) It does occur to me that a word like "planet" is very different from words like "fruit" or "work" in that the general public has no independent experience with planets, so the scientific definition has to be the only definition. Contrast fruit, where the common definition requires it to be sweet (thus excluding the tomato) or work, where the popular and scientific terms only vaguely match. No one is bothered by this conflict, and scientists are free to redefine either term without much notice from the public.

But for "planet" the only defiinition that matters is the scientific one. The public cannot create its own term, since it has no use for it. Some special term for the eight planets the public can actually see with (at most) binoculars probably makes sense, but even that's weak; almost no one is looking.


(1)

"We've already established that this claim is false?" Where? I've asked for an example of a scientific use, and none has been supplied. The burden of proof on something that hasn't been demonstrated is not to suppose its existence and ask someone else to prove its nonexistence.


(2)

Tempting, but false observation, that observing the planets is inherently science. Observing the planets is not inherently science any more than looking at Niagara Falls, a snowfall, a map of Belgium, or Playboy magazine is inherently science (geology, meteorology, cartography, and anatomy, respectively). Observing the planets is, by default, the enjoyment of pleasant scenery.

It's certainly true that for Pluto, only someone with a very serious telescope at their disposal can initiate their own observations, but anyone with an Internet connection can go to

http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-pluto.html

and gaze to their heart's content and see the very same best pictures of Pluto that any expert can. And it's not science to do so.

So I don't think that scientists "own" Pluto any more than they own Mount Fuji.

AOL released the logs of 35 million web searches their users had performed. 1085 of them contain the substring "pluto" but aren't "plutonium" or "plutocracy". Perhaps half of them either explicitly contain "planet" as well or are obviously about the icy body out there. If that same rate applies to other web searches, then there are about 5000 web queries about Pluto every day (in English). I'm betting not very many of those people are scientists. They're treating Pluto, with the tools they have at hand, the same way visitors to the Grand Canyon treat it. There's affection to it, and it's not science.



Posted by: nprev Aug 14 2008, 05:30 AM

QUOTE (JRehling @ Aug 13 2008, 10:05 PM) *
...there are about 5000 web queries about Pluto every day (in English). I'm betting not very many of those people are scientists. They're treating Pluto, with the tools they have at hand, the same way visitors to the Grand Canyon treat it. There's affection to it, and it's not science.


Good point. Honestly, and I almost gag to say it, but isn't this more of a PR issue than a scientific one?

We have a general category for sure: "things that orbit stars." Other stars doing so are easy to exclude, obviously. Thinking at this general scale, other things...not so much. Debris & leftovers from the key stellar formation event, really.

I'm not gonna state a position, just trying to provide another perspective. Maybe a planet is just what we think it is, if you can dig it.

EDIT: Dammit, after some more thought, I do want to state a position. I finally caught the logic behind IAU's current schema. "Minor planets" has long been the categorical definition for asteroids, which was no problem until KBOs came to light. Made sense; they were clearly not comparable to the classical planets.

Pluto was long thought to be possibly Earth-sized throughout much of the 20th Century, but always an anomaly. After 1978, we knew it was only half the diameter of the Moon, but nobody complained; after all, it had a moon of its own. Merely 20 years or so later, it became obvious that there were a host of objects not too different from Pluto in many ways. Then came Quaorar. And Sedna. And, finally, Eris.

Okay. This might work. I propose a new class of objects: "Plutoids" (not to be confused with "Plutinos", which share orbital similarities with Pluto but not other significant properties). Plutoids are objects of Pluto's diameter or better (but not exceeding the diameter of Mercury) that reside in the outer Solar System. They are a class unto themselves, modeled after the minor planet precedent. Anything smaller than the prototypical Plutoid is by definition a lowly KBO; anything larger than Mercury is by definition a planet.

Since I am utterly certain that everyone will accept this construct with tears of joy & starry-eyed admiration for me, my only request is that the Nobel Prize (along with the check) is mailed to me promptly. (Very promptly, if you please, because the rent is due & I don't want to hock more of my shiny metal...) Thank you, and good night! tongue.gif

Posted by: djellison Aug 14 2008, 07:40 AM

Yet again, a thread on this topic is getting heated again, despite warnings about it.

After todays debate, the entire issue, and any associate debate, is going, formally, on the banned subject list.


Posted by: djellison Aug 14 2008, 09:44 AM

I now have my registration details, so I'm in - and have a question submitted smile.gif

Posted by: Juramike Aug 14 2008, 11:15 AM

QUOTE (djellison @ Aug 14 2008, 04:44 AM) *
I now have my registration details, so I'm in - and have a question submitted smile.gif


Yup. Me too. It was pretty tough trying to boil it all down to one concise question.

Anyone else submit one?

Posted by: surreyguy Aug 14 2008, 05:17 PM

Yeah - asking how the definition (whatever it is) will be used and/or the implications of not having one.

Posted by: djellison Aug 14 2008, 05:29 PM

I submitted two

1)

Dr Tyson has said in the past that if you moved Pluto into an Earth-like orbit, it would grow a tail like a comet which, for a planet, would be embarrassing.

However, if we moved Earth to a Pluto-like orbit, under current rules it would cease to be a planet given that Pluto's orbit is considered not to be cleared, and that, surely, is somewhat embarrassing as well.

Given that, does the panel think the definition of a planet should be derived purely from the properties of the body in question, or should the nature and location of it's 'home' contribute to a good planetary definition?



and

2)
Who's job is it to define 'planet' - and what should the purpose of any definition be?

Posted by: JRehling Aug 14 2008, 05:59 PM

Good overarching questions.

That discourse of George Lakoff's which I cited, briefly, has something to say about both of them, I think. He takes the example of biologists arguing about whether genetic histories or phenotypes should be used as the basis for classification. He says that there was lengthy and vociferous debate over it, with rival camps. When the "answer" is really a matter of cutting the gordian knot: Have both systems. If one kind of biologist finds it useful to classify things genetically, then by all means, why force the phenotype system upon them? And if the other camp finds it useful to classify things by phenotype, then why force the other system on them? It would be like forcing carpenters to decide between hammer-nail solutions and screwdriver-screw solutions. Each has its use. And while standardizing would make every tool box one tool lighter, it's better to have both.

With planets, per Doug's question (1), this question of WHERE vs WHAT has come up. Cutting the gordian knot is to say that they simply call for two systems of classification (if each is found useful). For a dynamicist, obviously WHERE is important. For someone studying the structure and evolution of planetary bodies, WHAT is the gist, and WHERE matters mainly because temperature has an effect on WHAT.

I think the IAU definition may be really useful to dynamicists (although a dynamicist would have to say). Whether using the term "planet" for that makes more sense than "nucleation site" or whatever is another matter. It would have a lot to say, perhaps, about why the biggest nucleation sites that haven't cleared their orbits are so much lighter than the ones that have.

But for what the rest of planetary scientists do, it has no use. And the question remains, does *any* definition have a real use in planetary science?

And for the layfolk making their 5000 web queries a day on Pluto, would any such definition have any use?

Before they'd tossed around two definitions, the IAU leapt to the conclusion that the three (or more?) groups need one definition.

I think countless examples have shown us that the answer to Doug's (2) question is that when groups need different terms, they end up with different terms. It makes the dictionary 0.0001% bigger, and language 0.0001% more ambiguous, but that ends up being preferred over Group A having to use Group B's word. If the clash is big enough, it won't stay that way unless you have the sort of authority that kept "Stalingrad" in place as a name for sixty-some years.

Posted by: nprev Aug 14 2008, 06:09 PM

This is parenthetical (what do I ever say that isn't? rolleyes.gif ), but it seems to me that the GPD is the first such scientific ruckus over classification outside of biology, at least during the modern era. Geologists see mixtures of rock types every day, for example, and there certainly isn't a dispute on whether a particular specimen (or even a formation) is igneous, sedimentary or metamorphic, or a combination of all the above.

It's odd how emotionally attached we seem to be to some issues but not to others.

Posted by: Greg Hullender Aug 14 2008, 06:54 PM

I asked them whether they thought we had enough examples of planets to frame a meaningful definition at all.

--Greg

Posted by: alan Aug 14 2008, 07:56 PM

It's started

Posted by: Juramike Aug 14 2008, 07:58 PM

I asked why we couldn't just expand the meta-term "planet" to the broadest definition, and let the researchers define their specific subgroups of interest when they publish.

Pity we can't vote on the questions. (I really like Doug's first question)

Posted by: nprev Aug 14 2008, 07:59 PM

"Let the Games begin!!!" tongue.gif

(Silent moment of appreciation for the cleaning crew after the meeting; it's really hard to effectively remove blood, sweat, and tears...)

Posted by: Juramike Aug 14 2008, 08:01 PM

Whoo-hoo! I'm in!

[Actually, hearing all the startup noises and fumblings is a riot! I swear I heard a "D'oh!" in there]
[Ooops, and I just heard one of the Words You Cant Say on Television]

Posted by: alan Aug 14 2008, 08:01 PM

false alarm, they were only practicing the introductions

Posted by: djellison Aug 14 2008, 08:06 PM

I hope so - I though it started at half-past smile.gif

Posted by: volcanopele Aug 14 2008, 08:13 PM

Never got confirmation email sad.gif

Posted by: djellison Aug 14 2008, 08:32 PM

It's working, but I'm getting no sound at all.


(I quite the stream and then started it again, and it started working)

Posted by: alan Aug 14 2008, 08:40 PM

which one is the 13th?

Posted by: djellison Aug 14 2008, 08:45 PM

Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, Charon, Eris, and Makemake.

Posted by: djellison Aug 14 2008, 08:46 PM

N deG T is wrong in thinking that Europe doesn't care. I don't think I've been to an astronomy society that hasn't had that debate.

Doug

Posted by: elakdawalla Aug 14 2008, 09:48 PM

I didn't get to see the end of it because in the 6-hour window in which my plumber could have showed up, he showed up during the debate, of course.

Any commentary on the value of this exercise? I'd like to hear more Europeans and Australians and etc. chime in on Neil's claim that only Americans care about this.

--Emily

Posted by: volcanopele Aug 14 2008, 09:50 PM

Interesting debate. I think the best point made, and Tyson made it, was that educators need to move away (as quickly as possible) from teaching the solar system by counting planets, by memorizing their names. That is not science. Perhaps if people were educated more on the richness of the solar system, knew more about the moons of the outer solar system, and about the properties of each of the types of objects, I don't think the planet debate would be as highly charged.

Posted by: volcanopele Aug 14 2008, 09:53 PM

And maybe the reason others may not be as interested is because planetary science is taught differently (perhaps better) in other countries. Here planets are taught as the be all and end all of planetary science, you might even learn a bit about their properties, but hardly anything is discussed about other objects, like moons. That's why something being called a planet seems so important here.

Posted by: belleraphon1 Aug 14 2008, 09:57 PM

All..

I am not going to get into a discussion of details (still in shock after walking away unscathed from a car crash yesterday that totaled my just paid off car).

But I think the debate was lively and just wish more people could see science panel discussions like this to see how science works. Loved watching it no matter what the position of the Dr. Sykes and Dr. Tyson.

I agree the simplest definition of as planet is that the object is massive enough to undergo hydrostatic equilbrium.

I agree that under that simple definition can be many sub categories.... to reflect the richness of these bodies in the
universe we share.

Really loved the discussion.

Craig


Posted by: Stu Aug 14 2008, 10:01 PM

QUOTE (elakdawalla @ Aug 14 2008, 10:48 PM) *
I'd like to hear more Europeans and Australians and etc. chime in on Neil's claim that only Americans care about this.


Well, my views on this are well known and I'm not going to repeat them here. But I will comment on what's been said.

I respect NDgT a lot, as an Educator, broadcaster, writer and scientist, but IMO that was a rather silly and slightly arrogant thing to say and was very disappointing to hear. At the time of the IAU Conference it was BIG news, all over the TV and radio; my local BBC radio station and ITV TV station interviewed me on air about it. I was asked by countless people about what was going on. It was crazy. Now that has died down, but this is a subject that still generates a lot of interest, debate and passion over on this side of the pond. We have two astronomy monthly magazines here in the UK, and both have ran features on the debate and have featured letters and emails from readers. As Doug said, every astronomy society over here will have discussed the subject, and views are entrenched on both sides. smile.gif

So, to suggest that this is only of interest to Americans is ridiculous, and disappointingly elitist.

Stunning news, I know, but over here we have electricity and running water now. laugh.gif Oh, and a space agency, too. tongue.gif We have thousands of astronomical societies, and bookstores full of books on astronomy and space. UMSF has many European members, as does TPS, I'm sure. To suggest that none of them care about this is just wrong.

Posted by: Juramike Aug 14 2008, 10:02 PM

One take home message I got (and I think Tyson made this point) was that it was OK to ignore the IAU ruling.

I'm cool with this, we usually ignore most of the IUPAC [International Union of Pure and Applied Chemistry] nomenclature rules during our everyday work. As long as we all know what we're talking about, it's cool.
["A picture is worth a thousand words, ten thousand if it's IUPAC"].

For the future, I'll just make a point of clearly defining the individual items if I ever use a blanket term that could be ambiguous.

-Mike

Posted by: surreyguy Aug 14 2008, 10:08 PM

My sense is that in Britain that people who only have a passing interest in astronomy would be amused or bemused, but we don't have the kind of reaction from the public that Tyson described about his planetarium.

I found the debate more enlightening than I expected so a definite plus there. The contrasting aesthetics came across very well, I thought: Tyson's description of how his planetarium is organised, and Sykes's vision of Ceres.

Posted by: Greg Hullender Aug 14 2008, 10:14 PM

QUOTE (elakdawalla @ Aug 14 2008, 01:48 PM) *
Any commentary on the value of this exercise?


When Mark Sykes pointed out that most Planetary Scientists aren't in the IAU, it convinced me they should just formalize their own definition and use it in their publications. From what Sykes said (and what we've heard from Alan Stern here), Planetary Scientists seem to be pretty close to a consensus on what sort of definition would meet their needs. Perhaps Allan Stern and Mark Sykes might write up something.

--Greg

Posted by: djellison Aug 14 2008, 10:19 PM

QUOTE (elakdawalla @ Aug 14 2008, 10:48 PM) *
. chime in on Neil's claim that only Americans care about this.


I said a rude word when he said that. Quite loudly. Complete and utter...bu.....umm....nonsense. Every astronomy society I've been to up and down the country has had this discussion. London to Liverpool, I've had it with friends, family. Not as passionately as N de GT (who is?) - but still, it happens.



Posted by: JRehling Aug 14 2008, 10:38 PM

QUOTE (volcanopele @ Aug 14 2008, 02:50 PM) *
educators need to move away (as quickly as possible) from teaching the solar system by counting planets, by memorizing their names.


As a parent who has recently stocked up on a very large number of planet-related books for my son, I have a large number of gripes about their contents. A lot of these take the form of "fallout" from something innocuous higher up the research food chain. For example, my son wants to know why pictures of Venus's hillsides have big black stripes across them. It's where Magellan lacked data. There's nothing inherently wrong with data releases that handle the blanks that way, but when they appear unexplained in a kids' book, they distract quite a bit from the topic. False color images are another issue. When a kid's seen green stripes on Saturn in one picture, it's hard to explain infra-red radiation. It really puts the cart before the horse -- it's an explanation that's perfectly fine for some future day, but it is hell to make, unwittingly, the intro.

The almost total deemphasis of non-planets is another. I couldn't find a kid's book on Io, Europa, or Titan; definitely not in the Spanish language, which I'm using to read to my son. The books imply that it's more important to know how many satellites Uranus has (quick quiz -- anyone on here know without looking?) than what any of them are like. Or, lord forbid, that any of them might actually be as interesting as the planet itself.

This goes to the broader issue of how outreach could be improved. In my opinion, quite a bit. I think the screensaver images I created of the major solar system bodies (many thanks to people in this forum) are so dramatically superior, as a set, to any I've seen illustrate any book. I wonder how many kids have looked at ancient photos of Mercury and asked their parents why it has a checkerboard pattern and gotten a blank or spurious reply. In place of actual learning that could be happening.

I reckon Pluto is beheld by kids more than by scientists, and while it would make no sense to foist a kiddie definition upon the scientists, neither is it good education to foist a tortured dynamical definition on them. Shoot, we're talking about kids who won't learn what an ellipse is for another six years.

Posted by: Astro0 Aug 14 2008, 10:53 PM

Just to chime in...

We here in Australia have the same reaction to that comment about 'only Americans care about this'.
The discussions I have seen here in magazines, in astronomy clubs and from the ten thousand plus students that I talk with every year, there is considerable interest in the outcome of the ongoing debate about Pluto (and other worlds) status.

I find kids feeling 'sad' for Pluto, teachers confused 'is it a planet, dwarf, plutoid and next week what?', and the public wondering if Pluto just disappeared (or on several occasions, 'blown up!').

On the weekend, we are holding our Open House at the Canberra DSN and one of the talks I will give is on this very subject.
It will be a packed room and I'll guarantee that every person WILL 'care about this'!

Posted by: Stu Aug 14 2008, 11:00 PM

QUOTE (JRehling @ Aug 14 2008, 11:38 PM) *
As a parent who has recently stocked up on a very large number of planet-related books for my son, I have a large number of gripes about their contents.


Welcome to my world! laugh.gif You have no idea how many discussions/heated discussions/arguments I've had with various publishers and editors over the content of my books. It's a constant battle to persuade them to use images that are realistic and "true" over ones that "look nice" or "dramatic" but give a very false impression of what's Out There. I actually had a fight over that Magellen image you mention; after getting the editor to understand that no, there weren't ACTUALLY black stripes on Venus, I then had to try and persuade him that unless we could explain the true "false colour/radar image" nature of the pic then the readers would be given a very false impression. I won that one. But I have lost many arguments, including ones re the use of those garish classic "false colour" Voyager images of Saturn and Uranus, and hideously over-coloured images of Mars....

rolleyes.gif

Thankfully the editor I'm working with now is very open to input and wants to make the book as up to date as possible, so agreed to postpone work on the Saturn spread until after the Enceladus encounter, and we're leaving a blank box ready to update the Pluto page at the last possible moment.

Posted by: Mongo Aug 14 2008, 11:53 PM

If anybody wants to continue discussing this topic after it has been banned here, I suggest the Yahoo Group http://tech.groups.yahoo.com/group/majororminor/

It has been two years since it was last active, but it's still available.

Bill

Posted by: alan Aug 15 2008, 12:00 AM

QUOTE (djellison @ Aug 14 2008, 03:45 PM) *
Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, Charon, Eris, and Makemake.

After they added Makemake the IAU site said there were 4 dwarf planets.

I thought maybe a new one had been added and hadn't been officially announced yet, perhaps the debaters were including Charon in their own list even though at least one of them mentioned that the IAU doesn't recognize it.

Posted by: tedstryk Aug 15 2008, 03:07 AM

JRehling makes an excellent point. While memorizing the nine planets has been a cornerstone in schools, the dirty little secret is that teaching about the planets this way has been unsuccessful - most people forget it after the quiz is over, and it does nothing to inspire interest. The emphasis on the number of moons probably dates back to pre-space age time when we didn't know much more about these moons than how many there were and their very approximate sizes. But it definitely is less than inspiring.

Posted by: JRehling Aug 15 2008, 03:40 AM

A vivid memory of mine on the "planet bias" is the National Geographic poster of the Moon that came out in the Apollo era. I had it hanging on my wall in the early 70s, and again in the late 90s. It had a series of circles showing all of the solar system's largest satellites to scale. Each and every one of them was a silvery disc, identical except in size. The culture shock ("science shock"?) of seeing the cover of Science with the montage of the Galileans was world-shaking. Jupiter looked about the same way it did in the Pioneer images, which were decent, but the Galileans -- all four of them -- were stunningly complex. Seeing any one of them like that would have been jawdropping, but to see four, and no two of them alike, was incredible. I don't think another moment could be as surprising. Even Huygens, because we hoped to see what it found. Nobody even hoped to see the Galileans like that.

There is a law of small numbers that applies. Kids don't learn the entire periodic table (in my experience, anyway). Too many items. Kids in the US may learn 50 state capitals.

I made my son a screensaver of the planets and the most interesting satellites plus Ceres and Vesta, set them to scale but using a fourth-power of radius, so that places like Miranda and Vesta have visible detail while preserving the relation of which worlds are larger and which are smaller. And he learned all the names. I refer to the whole set as "planetas", but I add in that some of them are "lunas" of the others. I was pretty arbitrary in choosing the set, mainly going with the ones that had decent imagery available -- no Eris. And when the time comes to fill in more details on what the various places are like, we can fill those in. The total set numbers about 21, and I just don't describe the set as being of some magical size, the way English-speakers learn there are 26 letters and most of us learned there are 9 planets. To me, it's a lot less important for there to be a set of comfortingly fixed size or that the boundary be objective (I included Titan, Iapetus, and Enceladus, but not yet Dione or Rhea or any other Saturnian satellite). All I cared for was that he learned a bunch of them, that they were pretty, that he learned a tidbit or two about some of them -- hottest, biggest, smallest. Having known them all when he turned 2, I think he's gotten a pretty good introduction (he could see it from the chair where he eats). And I can't imagine anything that would have gunked it up more than having to explain categorization schemes.

Posted by: nprev Aug 15 2008, 03:52 AM

It'll stick, JR. smile.gif Check this:

"Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars, Pluto, Mercury, the Moon."

Memorized from the poster my Dad gave me when I was 2 or 3, in order of size as thought at the time. It sticks; and how I wish I still had that marvelous, magical poster! (Word of advice: Be sure to preserve these things for him, if you can; they are literally talismanic in later years.)

Posted by: ElkGroveDan Aug 15 2008, 04:53 AM

QUOTE (JRehling @ Aug 14 2008, 07:40 PM) *
the National Geographic poster of the Moon that came out in the Apollo era. I had it hanging on my wall in the early 70s,


Gosh during that time, the "Moon" poster hanging on my bedroom wall was http://www.thesequencers.us/DarkSide/images/recordposterdarkside.jpg. I still dream about green pyramids to this day.

Posted by: David Aug 15 2008, 11:57 AM

QUOTE (nprev @ Aug 15 2008, 04:52 AM) *
It'll stick, JR. smile.gif Check this:

"Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars, Pluto, Mercury, the Moon."


Of course, Pluto was off by a bit sad.gif

Nowadays it should be:

"Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars, Ganymede, Titan, Mercury, Callisto, Io, the Moon, Europa, Triton, Eris, Pluto."

Posted by: tedstryk Aug 15 2008, 12:50 PM

QUOTE (David @ Aug 15 2008, 11:57 AM) *
Of course, Pluto was off by a bit sad.gif

Nowadays it should be:

"Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars, Ganymede, Titan, Mercury, Callisto, Io, the Moon, Europa, Triton, Eris, Pluto."


When Pluto was discovered, we expected it (along with Triton) had a very low albedo (it turns out it has a very high albedo). Additionally, we thought the light from Pluto and Charon came from one object. I once saw an estimate suggesting its diameter was 6000 km!

Posted by: JRehling Aug 15 2008, 01:32 PM

I had a book with an illustration showing Pluto as a mirrorlike body of which we could only see the "reflected highlight" -- a circle of opposition surge -- while the majority of its apparent area was dark and unseeable.

The same book had an illustration of a volcano on Mercury in the "twilight zone" (permanent dusk, since the planet was thought to have tidally locked on the Sun) belching gas into a thin atmosphere, and snow clinging to rocky spires on Titan, with a ringed Saturn hanging in a blue sky. Beautiful fictions all around.

The admirable thing is how memorable images like that are. The real solar system has stuff that cool -- just not those particular things.

That book even managed to break the planet-only bias by including an illustration of Titan.

Per Jason's and Stu's complaint, it may be possible that book publishers know (the same way that advertisers who sell Cola know their line of work) that a book that *doesn't* feature the planets will lose out in sales to a book that gave Io, Europa, and Titan more attention than Mercury and Uranus. It's possible that a very important part of the lenses through which the population ends up viewing the solar system is a sales-time reaction to hunt for the "planets" (choir of heavenly angels sings) in all of their primacy and countability.

Posted by: Stu Aug 15 2008, 01:55 PM

QUOTE (JRehling @ Aug 15 2008, 02:32 PM) *
Per Jason's and Stu's complaint, it may be possible that book publishers know (the same way that advertisers who sell Cola know their line of work) that a book that *doesn't* feature the planets will lose out in sales


That wasn't actually my complaint; my complaint was over inappropriate, misleading and inaccurate images Full Stop, usually "false colour" images being used over beautiful real colour images. Case in point: whilst writing my latest book I had to fight for 3 days to get them to use a real colour photo of Victoria Crater instead of a false colour one. It didn't matter that the spread was called "Mars: the Red Planet", they wanted to use a false colour image showing VC in vivid blues and greens because it "looked more dramatic". I won, but only when I offered to let them use one of my colourisations of the same scene - with appropriate credit to NASA, etc, of course.

Posted by: Juramike Aug 15 2008, 02:25 PM

QUOTE (David @ Aug 15 2008, 06:57 AM) *
Nowadays it should be:
"Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars, Ganymede, Titan, Mercury, Callisto, Io, the Moon, Europa, Triton, Eris, Pluto."


Remember to stick those guys in http://www.exoplanet.eu/catalog-all.php. smile.gif

-Mike

Posted by: Greg Hullender Aug 16 2008, 01:15 AM

QUOTE (nprev @ Aug 14 2008, 08:52 PM) *
"Jupiter, Saturn, Uranus, Neptune, Earth, Venus, Mars, Pluto, Mercury, the Moon."


I tend to think of them by mass, though:

Jupiter, Saturn, Neptune, Uranus, Earth, Venus, Mars, Mercury, Ganymede, Titan, Callisto, Io, The Moon, Europa, Triton, Eris, Pluto, ...

http://en.wikipedia.org/wiki/List_of_Solar_System_objects_by_mass

--Greg

Posted by: nprev Aug 16 2008, 02:07 AM

Cool article! I'm going to be thinking of planets as objects in the yottagram range from now on! smile.gif

Posted by: Stu Aug 16 2008, 12:52 PM

An http://www.sciencenews.org/view/generic/id/35319/title/Upgrading_a_moon possible for Charon..?

Posted by: David Aug 16 2008, 01:27 PM

QUOTE (Stu @ Aug 16 2008, 01:52 PM) *
An http://www.sciencenews.org/view/generic/id/35319/title/Upgrading_a_moon possible for Charon..?


QUOTE
But Charon isn’t quite a planet either. One IAU criterion for a planet is that it clears its neighboring region of other want-to-be planets, called planetesimals. Charon has not done this since it hasn’t gotten rid of Pluto, Noll notes.


And the Earth hasn't got rid of the Moon. Does that mean we are now a dwarf planet?

I still don't know what "clearing the neighbourhood" means, but I should have thought it included ending up in an orbital relationship.

QUOTE
But, he countered, the IAU decided that when a satellite orbits its parent body, the center of gravity between the two must lie within the parent body.


There is something rather arbitrary about this criterion; for one thing, it depends upon the diameter of the body, which in turn is going to depend upon materials and density -- and the relationship might not even be constant. What would be argued of a system where the common center of gravity floats above a solid or liquid surface, but well inside an atmosphere? What about a center of gravity which is sometimes above, sometimes below the surface? That might already be the case for some of those binary asteroids or irregularly-shaped KBOs with moons.

Posted by: djellison Aug 16 2008, 01:33 PM

QUOTE (David @ Aug 16 2008, 02:27 PM) *
There is something rather arbitrary about this criterion;


Name a criterion to separate 'planet' and 'moon' that isn't.

Posted by: JRehling Aug 16 2008, 01:35 PM

The "binary" definition is definitely a separate matter, but similarly interesting.

I really find it odd that it could actually depend upon the time in the cycle. Suppose the barycenter passed through the tallest mountain on a world, but nowhere else.

Moreover, the barycenter of Sun-Jupiter is outside the Sun. I think that's a nail in the coffin right there.

Masswise, too, things tend to be more profoundly disparate than the barycenter measurement indications. Sun and Jupiter. Earth and Moon. Those primaries are obviously much more massive than the secondaries. Charon is only 14% the mass of Pluto. Maybe mass fraction is a better statistic to use, with some arbitrary threshold. At least it wouldn't depend upon the time of day.

Posted by: nprev Aug 16 2008, 02:29 PM

sad.gif ...is anyone else as tired of this debate as I am?

Not to denigrate the fine discussion & many valid points made, but boy would I love to see some closure. More & more I favor the "classical planets" concept: we got 9, that's all there is, unless we find something truly huge way out there someday.

Simplistic, yes...but since this whole thing is by now glaringly subjective, why not keep it simple? "Planet" is an honorary term in some ways, really; it's ancient as well. Maybe the line should be drawn temporally. Pluto was discovered in 1930, and was the last undisputed discovery of a planet; maybe it should be the last such, period. Anything else found has to be Mercury-sized or better to qualify.

Arbitrary? You bet. Unscientific? Yes, of course, because this is really not about science at all, it's about categorization & public perceptions. Still, this seems to make as much sense as other proposals with the added advantage of keeping the criteria understandable & easily applicable to new discoveries (and there's gonna be a LOT of them; just wait. We ain't seen nothin' yet.)

Posted by: djellison Aug 16 2008, 02:35 PM

QUOTE (nprev @ Aug 16 2008, 03:29 PM) *
sad.gif ...is anyone else as tired of this debate as I am?


Like you wouldn't believe.

Posted by: nprev Aug 16 2008, 02:37 PM

biggrin.gif ...My incredible psychic powers did not fail me!

Posted by: Stu Aug 16 2008, 03:05 PM

Why is everyone so down on this debate and this process? rolleyes.gif People with a professional scientific interest are having their say... experienced amateur astronomers are having their say... enthusiastic skywatchers with no scientific background but a fascination with Out There are having their say... kids learn about the variety of objects in the solar syatem through it... the public were able to watch a quite historic debate on the internet, live... science is working before our eyes...

Much better to have this discussion, I think, than to just say "Whatever" with no opinion at all when a decree like this is handed down from above. Shows we're not sheep happy to trot in whichever direction the sheepdog wants. smile.gif

Posted by: djellison Aug 16 2008, 03:15 PM

QUOTE (Stu @ Aug 16 2008, 04:05 PM) *
Why is everyone so down on this debate and this process?


"They can't even decide what a planet it - what's with that?"

Science does not come out of this well. Teachers are confused, students are getting mixed messages, text books are right today and wrong tomorrow. It's a bit of a farce - I wish it would just go away because ultimately it just doesn't matter. At the very best, this situation will end with headlines such as "After 5 years debate, Pluto IS a planet" or "6 Years on, Planet debate rages on" or "7 year itch, science squabble over Pluto continues" or "Planetary U-Turn, Pluto back in the pack".

Ever tried to explain why PLuto isn't a planet anymore? I'm embarrassed for science trying to explain it.

One word to sum up the entire thing

Crap

Doug

Posted by: Stu Aug 16 2008, 03:23 PM

All true, pretty much, but I still say it's better to get this sorted out now than just bury our heads in the sand and pretend the problem's not there. It is there, it's not going anywhere. I was really fed up with this too, a while ago, thought it was a huge mistake, and I still think the Pluto decision was wrong and the IAU were ******** idiots for shrinking Sol system's planetary population instead of increasing it, but hey, water, bridge... rolleyes.gif

I've decided I should use this as an opportunity to get people talking about and interested in planets, of our own Sun and of others out there, and just get people interested in astronomy in general. There's a lunar eclipse tonight, but the weather is so rubbish here in Kendal right now that it's unlikely we'll see it. But people will still go up to the castle anyway, on the off chance, and they'll hang around a while in the hope of the cloud clearing I'm sure. As they wait we'll talk to them, about Phoenix, the Hubble repair mission, ths ISS, and also, yes, Pluto and the "Great Debate".

Posted by: djellison Aug 16 2008, 03:27 PM

QUOTE (Stu @ Aug 16 2008, 04:23 PM) *
better to get this sorted


I think it's been fairly well demonstrated that 'science' is unable to sort this for itself. Two years on and we still have a nonsensical definition, a shed load of confusion, and frankly, a rather embarrassing 'debate' webcast that achieved 9/10ths of 4/5ths of exactly nothing. Some scientists made this mess, and science in general is incapable of resolving it.

This isn't a good thing.

Posted by: belleraphon1 Aug 16 2008, 03:29 PM


I am a bit tired of of the debate but at the same time it is refreshing to see the public's attention perk up.

The silver lining in all this is that due to the incredible advance in our observing technologies we are finding all these new objects out in the Kuiper Belt and around other suns. The entire reason the question even came up is because of all these new discoveries....

The solar systems we are finding out there are very different in architecture to our own serene system.
http://astronomynow.com/080807ComputersimulationputsSolarSysteminitsplace.html

Delight in the fact that we are learning new things and discovering new worlds and worldlets at an increasing pace.

Great time to be alive....

Craig





Posted by: Stu Aug 16 2008, 03:30 PM


Ever tried to explain why PLuto isn't a planet anymore?

The number of Outreach talks I give? Hmmm, yes, just a few times... laugh.gif

It usually goes something along the lines of "A tiny number of a small bunch of unelected people decided to turn history on its head and mess up something that wasn't messed up in the first place. But that's not the end of the story yet, so watch this space. In the meantime, if you want to think of Pluto as a planet - like me - fine; if you don't, that's fine too. Eventually heads will be banged against brick walls and sense will prevail. Until then, look at this picture of xxxx That's actually a..."

smile.gif

Posted by: nprev Aug 16 2008, 03:39 PM

laugh.gif ...good summary!

I honestly think that the "classical planet" concept will prevail. It makes the Solar System something relatively simple to visualize, yet allows room for all the other exotic critters.

Posted by: belleraphon1 Aug 16 2008, 03:41 PM

And ya know...

Life is messy and so is the universe. I found the debate lively, and unstodgy. Scientists ARE human afterall. Falleable and as full of emotion as any one else.

It really does not matter how this falls out..... Pluto is still Pluto, Enceladus will still be geysering, the hydrocabon dunes of Titan will stll advance under the nitorgen/methane winds, and we will continue to be amazed and humbled at the wonders all around us.

Have to go watch my grandsons now.... I wonder what wonders they will know when they reach my age?

Craig






Posted by: belleraphon1 Aug 16 2008, 03:50 PM

Stu...

and I apologize in advance because I am not currently a speaker to the public.... so I am not trying to presume anything here
and you may have already mentioned this, but one way to introduce to children the reason this debate is happening is BECAUSE we are learning SO many new things about these worlds and the universe that we are not so sure about our old definitions. And, my goodness, what wonderful things might THEY discover in the future that will turn definitions on their heads?

This is how science works.

Craig

Posted by: alan Aug 16 2008, 04:36 PM

QUOTE (Stu @ Aug 16 2008, 07:52 AM) *
An http://www.sciencenews.org/view/generic/id/35319/title/Upgrading_a_moon possible for Charon..?

QUOTE
when a satellite orbits its parent body, the center of gravity between the two must lie within the parent body

Don't all the objects in a system orbit the barycenter? It the barycenter is outside the surface of Pluto what about Nix and Hydra?

Posted by: Stu Aug 16 2008, 04:45 PM

QUOTE (belleraphon1 @ Aug 16 2008, 04:50 PM) *
This is how science works.

Craig


Yep, that's one of my (**Outreachbabble Alert**) "Core Messages" and one of the reasons why this whole debate can be useful. Kind of a "lemons into lemonade" thing smile.gif

Posted by: Juramike Aug 16 2008, 06:49 PM

QUOTE (Stu @ Aug 16 2008, 10:30 AM) *
Ever tried to explain why Pluto isn't a planet anymore?


Heck, throw the question back at them:
"What do you think it should be?" "Here are some objects in our solar system and some we've found elsewhere, where do you think it fits in?"


If you don't like the IAU decision, don't follow it. From here on in, I'm making up my own list.
I call my current set "round and possibly-differentiated bodies that orbit stuff"; everything else is a "rock" or an "ice chunk".

Discoveries will and should be always able to change the status quo. The definitions need to be flexible and adaptable or they quickly become irrelevant.

[EDIT: And no, I don't view the New Horizons mission as a checkbox visit to the "last planet"; I view it as the first mission to a completely new and important kind of planetary object: I expect huge surprises and discoveries at Pluto and major implications for other stuff "out there".]

[/flame off]

-Mike

Posted by: Patteroast Aug 16 2008, 09:47 PM

The current decision never seemed as terrible to me as many make it seem... honestly, the only part I think doesn't make sense is the part where dwarf planets aren't planets. Hydrostatic equilibrium seems to be a point that a lot of people agree on. Why not leave it at that and talk about different kinds of planets? Eight major planets, four of them terrestrial, four of them gas giants, plus at least four dwarf planets, and a bunch of planet-moons... none of this seems to have much conflict with our current understanding of the solar system.

In any case, I think this isn't a huge problem... just a quibbling sort of thing that keeps going on. And I've explained the reasons the IAU had to demote Pluto to several people, without many problems.

Posted by: djellison Aug 16 2008, 10:16 PM

QUOTE (Patteroast @ Aug 16 2008, 10:47 PM) *
four dwarf planets


It's not unlikely (indeed many suggest it is quite probable ) that a KBO the size of Mercury, Mars, or ever larger, will be found in the not too distant future. Would you call that a dwarf planet?

Doug

Posted by: mchan Aug 17 2008, 12:33 AM

If and when a Mercury or larger sized object is found in the Kuiper Belt, the planet debate will be reinvigorated and be more widespread.

The current debate and the discussions on this thread have been useful to me in changing my view of the definition of a planet.

Posted by: JRehling Aug 17 2008, 12:54 AM

I think there ought to be some robustness built in to ANY kind of thoughts we have on this. It's nice to contemplate what it would mean to discover an Earth-sized KBO, but it's silly to craft a definition that has trouble grappling with such a discovery.

It would be like if the law against murder listed the weapons that counted, and then when someone was killed with a spoon, saying "WHOOPS! Didn't think of that one!" The law on murder thereby shouldn't restrict it based on the weapon, and on the long list of things that don't make sense would be to craft a definition that would be in trouble if an Earth-sized KBO were found and then sit on pins and needles waiting to see if we find one.

No definition should be so brittle in the face of easily-imaginable discoveries. We all knew that Eris could happen before they found it. It wasn't like they found a large body composed of neutrinos or a cloud of 9 quadrillion fist-sized chunks of ice circling each other. Something that weird, fine -- let that challenge your definition. And from time to time, mind-blowing discoveries do happen. But a slightly larger Pluto is not a metaphysical mind-bender. Any thoughts on this ought to be open to a Neptune-sized body 0.5 light years out, whether or not one exists.

Posted by: laurele Aug 17 2008, 03:19 AM

QUOTE (nprev @ Aug 16 2008, 09:29 AM) *
sad.gif ...is anyone else as tired of this debate as I am?

Not to denigrate the fine discussion & many valid points made, but boy would I love to see some closure. More & more I favor the "classical planets" concept: we got 9, that's all there is, unless we find something truly huge way out there someday.


With all due respect, no. Not only am I not tired of the debate; I welcome it. Why do we need an artificial sense of closure when the issue is obviously so open ended, when there is still so much more we are learning that could change or at least amend the planet definition issue many times.

At today's session on educating the public, we discussed what an amazing "teachable moment" this can be if teachers and those who do public outreach actually teach the controversy. Educators can present the perspectives of both sides and then ask students to come to their own conclusions. Some model lesson plans by NASA were handed out at the session. There was a general consensus that teaching that there is an ongoing debate as opposed to coming down firmly on one side or another is a wonderful opportunity to develop critical thinking skills.

Another issue that came up is, what exactly constitues the Kuiper Belt? One of the speakers--I think it was Dr. Mark Sykes--discussed how the term "Kuiper Belt" is used to describe a very large region that is really separated into multiple sub-regions. Pluto and the Plutinos in 3:2 resonance with Neptune are not actually in the Kuiper Belt proper area, which is slightly further out. That is where most KBOs are concentrated, as was displayed on a graph. Then there are the Scattered Disk Objects, which are at an even further distance and are literally scattered all over the place rather than located in the main clump of the Kuiper Belt. This data is very new and suggests Pluto may not be a Kuiper Belt Object after all.

With so much new data constantly coming in, with New Horizons on its way to Pluto and the Kuiper Belt, we know we're going to learn more about this region in the next few years than we have ever known to date. We know the study of extrasolar systems will bring us new data as well, data equally likely to surprise us. In light of this, why artificially cut off debate on what constitutes a planet? The reality is, this discussion has been ongoing and evolving for centuries and likely will continue to do so. Imagine if people had sought closure after the discovery of Uranus or Neptune, or even further back, after the heliocentric model of the solar system was first accepted in the 17th century. Would all the later data have been ignored because "we already had a consensus" and people didn't want to reopen the issue?

The prevalence and persistence of this debate means the public, at some level, is expressing interest in astronomy. It may not be from as broad a perspective as some people would like, but it's a start. Interest in this issue just might bring more people to a planetarium, observatory, or astronomy club and excite a new interest in the field. How can that not be better than having the public pay no attention and instead spend their time reading about Paris Hilton or Lindsay Lohan?

Posted by: nprev Aug 17 2008, 03:48 AM

QUOTE (laurele @ Aug 16 2008, 08:19 PM) *
The prevalence and persistence of this debate means the public, at some level, is expressing interest in astronomy. It may not be from as broad a perspective as some people would like, but it's a start. Interest in this issue just might bring more people to a planetarium, observatory, or astronomy club and excite a new interest in the field. How can that not be better than having the public pay no attention and instead spend their time reading about Paris Hilton or Lindsay Lohan?


Mmm...very tempted to agree with you. However, I don't do outreach myself, so would be interested in Stu's and Doug's opinions. I get the feeling from them that the GPD isn't making their lives any easier; the trade-off would be if it's making their audiences larger.

Do have to agree that anything pushing people off of celebrinoise is inherently positive, though. I just wonder what the magnitude of any such effect might be. Inclined to think that people who attend outreach briefings, pay attention to astronomical news, etc., already are too hip to devote much attention to tabloid-style nonsense.

Posted by: Greg Hullender Aug 17 2008, 04:13 AM

What makes the debate tiresome for me is two things: one, nothing new is said; people just keep repeating the same arguments over and over. Two, I seem to be unable to refrain from participating. :-)

--Greg

Posted by: nprev Aug 17 2008, 04:17 AM

I feel your pain, Greg... rolleyes.gif ...just when I think I'm out, it drags me back in!!!

Posted by: David Aug 17 2008, 04:22 AM

In reading through these responses I've realized something that I'd missed before about the debate.

I've never had much of a passion about the conclusion of the debate; I always had issues with the kinds of definitions that were floated, but I never had much invested in whether we had 10 planets or 8 or for that matter 25 (with all respect to the 'Classical Planets' option, I don't think that sticking with 9 planets is any longer a possible option).

But I realize there's another issue here; and it doesn't have to do with the facts of the case, or even with the technical side of astronomical taxonomies. It's about the progress of knowledge, and how it is presented.

To put it briefly: it's easy to explain "We used to have 9 planets, but now we have 10." "Why?" "Because we discovered a new planet we didn't know existed before." "Oh. Okay."

It's much, much harder to explain: "We used to have 9 planets, but now we have 8." "Why? Did the 9th one blow up?" "No, we changed our definition of what a planet was." "Why? What was wrong with the old one?" [...pause...] [...silence...]

It's easy for people to understand that discoveries are made, and new knowledge comes to the fore, and that they need to remember more things than their fathers before them. Classical civilizations knew three continents: Europe, Asia, and Africa. Columbus discovered South America (not in 1492 -- in 1498) and North America was discovered a short time later. Then people had to cope with five continents. Australia came along in the early 17th century and Antarctica in 1820. At no point has there been a serious attempt to reduce the number of continents (though it's long been apparent that the Europe/Asia distinction is artificial and arbitrary).

But to explain that, as it would seem, the process of discovery is going backwards -- that we are forgetting facts we used to know -- that we seemingly have less information than we had before -- this is very difficult to explain.

Of course, it's true that we really are learning more than we knew before, that our knowledge of the Solar System is much richer than before. But the logical corollary of that should be -- would be expected to be -- that we should ask non-astronomers to know more -- not to dumb down the Solar System into something that can be printed on the back of a mini-juice box. And I think it's the impression that we're taking a retrograde step, and raising a generation that not only won't know what the Kuiper Belt is, but won't even have ever heard of Pluto, that bothers folks.

Posted by: mcaplinger Aug 17 2008, 04:48 AM

QUOTE (David @ Aug 16 2008, 09:22 PM) *
It's much, much harder to explain: "We used to have 9 planets, but now we have 8."

Exactly! This is why I don't understand why we can't use a definition that keeps Pluto and doesn't make previously-known non-planets like Ceres planets. Calling anything Pluto-sized or bigger a planet would have that attribute, however "unscientific". I'd be happy to call Eris a planet.

But I also agree that we are saying the same thing over and over again in this thread, and I could imagine closing it for our own good.

Posted by: JRehling Aug 17 2008, 05:25 AM

QUOTE (laurele @ Aug 16 2008, 08:19 PM) *
At today's session on educating the public, we discussed what an amazing "teachable moment" this can be if teachers and those who do public outreach actually teach the controversy. Educators can present the perspectives of both sides and then ask students to come to their own conclusions.


That is great for students at a certain level. I'm not sure that that level is prior to graduate-level, however, and if it is, it's definitely not elementary or middle school material.

I could see an adult with interest in science finding the issue interesting and therefore concluding that it would be "amazing" to teach to young kids, but that alone wouldn't stop the effort from misfiring.

In an elite private high school, I first encountered the idea of contending systems of classification in tenth grade, and it was with things much more concrete than this.

For younger kids, this sounds like a lesson designed to be one of those where the educator speaks, heads nod, and the hour passes.

Posted by: Stu Aug 17 2008, 07:41 AM

QUOTE (JRehling @ Aug 17 2008, 06:25 AM) *
For younger kids, this sounds like a lesson designed to be one of those where the educator speaks, heads nod, and the hour passes.


If they're a rubbish educator, yes. smile.gif I have a hard time understanding how any teacher can make astronomy (there are planets with rings! a comet helped kill the dinosaurs! stars are enormous flaming balls of gas! when some stars die they turn into black holes that EAT other stars! Mars has a volcano 2x higher than Mt Everest!!) boring, but I've heard a few, or rather gone into a class after a teacher has "introduced" a class to astronomy and liquified their brains with a boredom ray, then I have had to try and stuff the gunk back into their skulls and get it to set again in an hour...

To be fair, most teachers simply don't have the time, resources or knowledge to cover the subject well - they have so many subjects to teach, it's hardly surprising - which is why they're (usually) very grateful to have someone come into a class and cover it for them, leaving them more time to deal with the Egyptians, the Victorians or whatever. Some teachers sit in on the talk and are as enthralled as the kids, as it's all "new stuff" to them too; others don't give a stuff and sit at the back, marking papers, preparing the next lesson, or flicking through the latest copy of "Celebrity Hello Ok Weddings", which is sad, and frustrating, and I want to grab them by the neck, Darth Vader style, lift them off the floor and tell them how they should be soaking up the info to pass on next time, but I don't. Besides, that kind of behaviour makes a repeat visit to a school rather less likely... laugh.gif

I've been on quite a - god, I hate this word, but I figure most people will relate to it so I'll use it - journey as an Outreacher with this whole Pluto thing. Before the IAU meeting I was pretty sure they'd leave Pluto alone and increase the number of planets in Sol system, not decrease it, and I even said as much in an interview feature thingy with my local TV station ("I think Pluto's safe," I said confidently into the camera, posing beside my telescope in the middle of the day. Shows what I knew, eh?). When the decision came down I was, frankly, furious. I saw it as a step backwards, and thought the IAU had bottled it, thrown away a chance to enhance the wonderous nature of the solar system, and tossed away an opportunity to show that astronomers and scientists can be bold and embrace new things and be, well, exciting! I thought the decision was cowardly and weak, and thought they had been pathetically meek about the whole thing.

( Of course, those opinions were based more on me being a die-hard (and often derided, lets face it) romantic and sentimentalist who has what many - here and elsewhere - believe to be an unrealistically melodramatic view of the universe and our place in it. I make NO apology for that, and never will; I'm not an engineer or a physicist, I'm just a guy who finds joy standing in a field at midnight watching shooting stars skate across the sky, who has actually cried when probes have landed safely on Mars, and gets all emotional thinking about the day Oppy or Spirit dies. Some people (not here, I hasten to add, although I can sense some people shaking their heads when they read my posts laugh.gif ) find that ridiculous, I know, but I don't lose any sleep over that; I'm confident and content that I see and feel the universe more personally and more intimately than they ever will smile.gif )

I wasn't angry because of any scientific arguments, which many others here are more qualified to make, I was angry because through my eternally rose-tinted telescope eyepiece it was just wrong, a step backwards. I loved the idea of the planetary population growing; it just seemed so exciting! I'd have loved telling kids that there were new planets in our solar system! I'd actually been looking forward to it! Now... now I had to tell them that one of the planets they already knew wasn't a planet anymore. How the hell was I going to explain that, 1) when it was scientifically complicated, and 2) when I didn't agree with a damned word of it?

Well, it's my job to do that, as someone who is allowed to go into schools and given the privilege, honour and enormous responsibility of standing in front of a group of kids and putting new information into their brains, info which is going to stick there, so you'd better get it right... So what I've been doing is putting both sides of the debate, whilst acknowledging that it's something I feel personally quite strongly about but asking the kids to just think about it, watch what happens, and consider the Pluto thing as part of the Big Picture. It hasn't been easy; I started off post-IAU decision very angry and quite flustered about it, and I'm sure I left a couple of classes more confused about the issue than they were before I started, but hey, I'm only human.

But now, having been educated about the science behind this debate - to a large part here on UMSF by people who I respect enormously - I see this as a great opportunity to educate kids about how science works and to get them interested in and talking about planets. And this most definitely is a subject and issue that young kids (and I'm talking 7-12 yr olds here) can be taught about, if you have the patience, enthusiasm and, yes, skill to put it across. Now I am able to tell kids about Pluto That Was, Pluto That Is, and speculate about Pluto That Will be When New Horizons Flies Past. I get to talk about the same planet in three different ways! Win, Win, Win! Sure, it's been an absolute disaster, the way it's been handled, and Doug's right when he says that it's been bad for science and has been a destructive thing; I personally think it has made the IAU and astronomers look like befuddled old boffins with wild white hair and stained lab coats who shuffle about their dusty observatories in a fluster, unable to make up their minds about something incredibly important. But we are where we are, and we can either gnash our teeth or smile and get on with it. A while ago I would have done the former, but now I try and do the latter, and I think that when I talk to a class about this I give them an idea of how important it is that science keeps moving on, taking note of changes and new discoveries, and coming out the other side better.

In an ideal world I'd be able to tell them that sometimes science CAN be sentimental and romantic, and do the Right Thing rather than the Accurate thing, i.e. leave Pluto as an "honourary planet" simply because of its wonderful history and place in people's hearts and damn the science, but I guess, sadly, that will never happen.

I saw Pluto once, through a big telescope. Looked like a star. Strangest thing tho... looking at it I felt quite moved. Not like I was looking at a star at all... smile.gif

Posted by: nprev Aug 17 2008, 07:59 AM

Well said (like it could be anything else??? rolleyes.gif )

I dunno, man, I just dunno in so many ways. Trying to understand why rocking the fabled 'planet boat' is really in anyone's interest. Does it serve science? Hell, no. Any philosopical/naturist benefit evident? No. Does it screw up public perceptions? (Gee, really don't have to type it...)

Not to bitch without offering at least one solution. Just return to the status quo ante, and just leave it. There's no harm, no foul. The debate was healthy, but what it ultimately reveals is that we are creatures of perception, and the Universe is not structured in absolutes. We learned thereby, and really that's the important thing, is it not? Certainly it's the only thing even remotely connected to science (another construct of ours, but proven most valuable over time).

Posted by: alan Aug 17 2008, 08:51 AM

Before the IAU stirred up the hornets nest by 'settling the debate' we had the planets and the minor planets with the minor planets divided into subcategories such as asteroids, kuiper belt objects, centaurs, damocloids etc. I'm among those that thought Pluto was in the wrong after they started finding larger KBO. Saying that I see no reason not to have dwarf planets count as planets although I think they should be distinguished from the eight that dominate their neighborhood which Stern and Levison referred to as Uberplantets ( http://www.boulder.swri.edu/~hal/PDF/planet_def.pdf ) The storm over the planet definition could have been avoided if instead of claiming the word planet for themselves those promoting the dynamic definition came up with a name for their favorite subcategory.

The one thing I never understood why so many plutophiles feel a compelling need to keep other objects out of their club. Whats wrong with having 12, 20 or even 50 planets? If we end up with 50 planets no one going to force you or any of the school children to memorize all of them. What will likely happen is children will learn the 8 largest and some selection of the more interesting dwarf planets, probably the largest one (currently Eris), Pluto (because its special), Ceres (because it was the first one found and is one of the few that kids can see for themselves using binoculars), Sedna (because its may be a member of the inner oort cloud). In doing so they will learn something about the structure of the solar system. If we were to go back to 9 or 10 we are more likely to preserve the system where most kids just memorized the list and learned little beyond it.

Posted by: JRehling Aug 17 2008, 02:36 PM

QUOTE (Stu @ Aug 17 2008, 12:41 AM) *
Well, it's my job to do that, as someone who is allowed to go into schools and given the privilege, honour and enormous responsibility of standing in front of a group of kids and putting new information into their brains, info which is going to stick there
[...]
It hasn't been easy; I started off post-IAU decision very angry and quite flustered about it, and I'm sure I left a couple of classes more confused about the issue than they were before I started, but hey, I'm only human.
[...]
But now, having been educated about the science behind this debate - to a large part here on UMSF by people who I respect enormously - I see this as a great opportunity to educate kids about how science works and to get them interested in and talking about planets. And this most definitely is a subject and issue that young kids (and I'm talking 7-12 yr olds here) can be taught about, if you have the patience, enthusiasm and, yes, skill to put it across.


I think you're giving the power of abstraction on the part of the educator way too much credit there. I have no doubt that an animated speaker can keep an audience's eyes on them while they read the phone book (I've seen it done, by Robin Williams, I think), but there's chain of ideas here that build on each other, and you can't, no matter how skilled or informed, convey Idea #1 in 3 minutes, have everyone with you, then convey Idea #2 which depended upon grasping Idea #1 in three minutes, have everyone with you, etc. and get to Idea #6 successfully. At each point in the chain, some fraction of the audience zones out, and a few links in, you're lucky if you have the One Bright Kid engaging you while the rest beg for him or her to be stricken down so this agony can end.

If that did work, then a skilled educator could have 8 year olds doing calculus after a series of 180 brilliant lectures. It only works if Gauss is the 8 year old. A lecturer is fully capable of giving those lectures and perhaps enjoying himself or herself quite a bit, but having the audience along for the ride requires a different audience.

I'm teaching the planets, too -- and I think it's easy to underestimate what a wildly abstract idea "clearing its orbit" is. First you have to have the idea that the orbit is a sort of permanent racetrack in the sky. But, scratch that idea of "permanent", because if they were all permanent than nothing would ever clear its orbit. You have to have the idea of larger bodies deflecting smaller bodies, and now you're trying to get the audience to accept the powerfully counterintuitive idea that gravity, which only pulls things towards each other, can sometimes end up pushing things farther away. If that were Idea #4 in the chain, you'd be providing the kids who only tuned in for that with a heck of a confusion. They get to tenth grade and tell the physics teacher that gravity can sometimes push things apart. The physics teacher tells him, no, you misunderstand, I don't know what some guy in the planetarium said, but please listen more closely next time, Johnny -- gravity pulls things together.

Posted by: Stu Aug 17 2008, 02:59 PM

I'm not saying I go into a class and give the 8yr old kids enough info to let them sit an astronomy exam biggrin.gif 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.

Posted by: nprev Aug 17 2008, 03:10 PM

Slight break from the ordinary...substitute "I Got 9" for "I Got 6" in this classic http://www.youtube.com/watch?v=cwkgNf69ihY. We could all use some humor & a bit of funk at this point. smile.gif

Posted by: K-P Aug 17 2008, 04:07 PM

My spoon clearly was missing in this soup, so... I shall reveal my un-objective, un-sincere and un-scientific vision here too. rolleyes.gif (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...


Posted by: nprev Aug 17 2008, 04:31 PM

...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.)

Posted by: JRehling Aug 17 2008, 04:41 PM

QUOTE (K-P @ Aug 17 2008, 09:07 AM) *
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.


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? smile.gif

Posted by: K-P Aug 17 2008, 04:51 PM

QUOTE (JRehling @ Aug 17 2008, 07:41 PM) *
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? smile.gif


...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.

cool.gif


Posted by: nprev Aug 17 2008, 05:11 PM

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!

Posted by: ElkGroveDan Aug 17 2008, 05:16 PM

QUOTE (K-P @ Aug 17 2008, 08:51 AM) *
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.

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.

Posted by: K-P Aug 17 2008, 05:20 PM

QUOTE (nprev @ Aug 17 2008, 08:11 PM) *
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.


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

ph34r.gif

(duck... and cover...)

Posted by: nprev Aug 17 2008, 05:37 PM

laugh.gif ...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...)

Posted by: stevesliva Aug 17 2008, 06:23 PM

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. wink.gif

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

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.

Posted by: Stu Aug 17 2008, 06:27 PM

QUOTE (stevesliva @ Aug 17 2008, 07:23 PM) *
And Stu, I thought rubbish was a noun? You've adjectived it. tongue.gif


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

Posted by: laurele Aug 17 2008, 09:08 PM

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.

Posted by: JRehling Aug 17 2008, 10:20 PM

QUOTE (K-P @ Aug 17 2008, 09:51 AM) *
...and personally I have always felt that Europe as a "continent" is not a proper expression.


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.

Posted by: JRehling Aug 17 2008, 10:33 PM

QUOTE (laurele @ Aug 17 2008, 02:08 PM) *
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.


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.

Posted by: vjkane Aug 17 2008, 11:12 PM

My problem with this whole debate is that it attempts to mix topics and goals. 'Planet' is an ancient term that has cultural meaning (and hence the fierceness of this debate). However, it is not a useful scientific classification. For example, Io seems to fit all the criteria for a terrestrial world except that it found itself orbiting a planet instead of the sun. However, the primary justifications I've read for a mission dedicated to Io is what it can tell us about the processes likely present early in the history of the other terrestrial planets.

Sometimes, a single world can fit multiple classes. Titan shares active weather systems in a dense atmosphere and a solid surface in common with Venus, Earth, and Mars. (Triton and Pluto's atmosphere's seem a bit thin for this class.) At the same time, Titan is a member of the class of icy bodies with internal oceans in common with Europa, Ganymede and possibly Triton and Pluto.

I think the scientists should accept that planet is a cultural term. They can and should come up with distinctive terms that classify bodies by their characteristics and not their place of orbit.

Posted by: djellison Aug 17 2008, 11:38 PM

This debate isn't getting anywhere. We're getting longer and longer essays that actually don't say anything. And we have ALL done it, despite it being explicitly banned in the rules. I let it go for a few days - but realistically, it's not going to go anywhere - so I'm closing it.

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