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The Great Planet Debate conference, August 2008 - Washington DC
Alan Stern
post Aug 12 2008, 01:57 AM
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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.
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Juramike
post Aug 12 2008, 02:17 AM
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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 "One of these things is not like the others" 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]


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nprev
post Aug 12 2008, 02:32 AM
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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.


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Greg Hullender
post Aug 12 2008, 03:44 AM
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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
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nprev
post Aug 12 2008, 04:34 AM
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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!!!


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volcanopele
post Aug 12 2008, 04:34 AM
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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


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lyford
post Aug 12 2008, 05:07 AM
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Ok, so if a planetary scientist were less than 5 ft. in height... no I don't really want to go there. huh.gif


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dvandorn
post Aug 12 2008, 06:17 AM
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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


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JRehling
post Aug 12 2008, 06:54 AM
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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.
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dvandorn
post Aug 12 2008, 07:09 AM
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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


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JRehling
post Aug 12 2008, 07:12 AM
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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.
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Stephen
post Aug 12 2008, 08:20 AM
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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

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Stephen
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Alan Stern
post Aug 12 2008, 11:47 AM
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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
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Phil Stooke
post Aug 12 2008, 02:03 PM
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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


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Phil Stooke
post Aug 12 2008, 02:05 PM
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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


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