The Great Planet Debate conference, August 2008 - Washington DC Options

[Patteroast]

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.

[djellison]

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

[mchan]

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.

[JRehling]

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.

[laurele]

...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?

[nprev]

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.

[Greg Hullender]

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

[nprev]

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

[David]

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.

[mcaplinger]

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.

[JRehling]

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.

[Stu]

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. 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...

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 ) 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 )

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...

[nprev]

Well said (like it could be anything else??? )

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).

[alan]

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.

[JRehling]

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.