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.

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"... ) 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. )

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! )--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.

======
Stephen

...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

Quite.

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?

"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".

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."

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.

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

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.

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:



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

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.

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

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

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