Author Topic: Pluto-Planet debate discussions  (Read 114377 times)

Online meekGee

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Re: Pluto-Planet debate discussions
« Reply #540 on: 04/03/2017 02:37 PM »
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Stern is clearly trolling, and IMO is doing so since he realized he can "energize" support for his programs.  There is no other reasonable explanation to him misunderstanding this.

Can you expand upon this?  What makes you think he isn't just expressing his opinion regarding which definition of planet is more useful from a geophysical perspective?   I haven't really seen any indication he's feigning a misunderstanding of the IAU definition.  It reads to me that he disagrees that the IAU definition is the best approach.  In the 2002 Stern & Levison paper the dynamical definition was presented as a refinement to the geophysical definition.  It was never argued that the word "planet" should be defined dynamically in that paper.  He hasn't changed his view on that.
First, the inconsistencies pointed out by others upthread.

Second, the timing. I remember it starting back then.

But of course this is just an opinion - that goes without saying.
ABCD - Always Be Counting Down

Offline Paul451

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Re: Pluto-Planet debate discussions
« Reply #541 on: 04/03/2017 05:01 PM »
The geophysical definition is more useful to the geophysicist.

As I tried to show in my comment, I don't think any of the proffered geophys definitions are useful. Whether roundness or arbitrary mass cut-offs. It either doesn't correlate to the differences that matter, such as composition or history, or doesn't correlate tightly enough with an actual distinction, such as internal differentiation.

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Stern is clearly trolling, and IMO is doing so since he realized he can "energize" support for his programs.  There is no other reasonable explanation to him misunderstanding this.
Can you expand upon this?

We have to be careful, Stern is apparently a member of the NSF, and under site rules there's a line that you can't cross when criticising other site-members.

What makes you think he isn't just expressing his opinion regarding which definition of planet is more useful from a geophysical perspective? I haven't really seen any indication he's feigning a misunderstanding of the IAU definition.

Do you think, based on his prior paper, that he is actually confused about the meaning of "cleared its neighbourhood" enough to be genuine when saying that Earth or Jupiter don't meet the IAU criteria? Do you think he misunderstands the IAU voting method enough to justify his claims of "less than five percent" of astronomers hijacking the debate? Do you think he didn't know of the role of his own faction in trying to ram his preferred definition through the first round (and being defeated by over 90%)? Do you think he doesn't understand enough on the history of science and of scientific committees to justify his acting like a vote on standardising nomenclature is somehow extraordinary and unprecedented? Do you think his denigration of his colleagues is appropriate behaviour for a scientist at all, let alone one in the public spotlight as his is? (For eg, likening astronomers to "podiatrists" doing "brain surgery" when categorising the solar system.)

Offline CuddlyRocket

Re: Pluto-Planet debate discussions
« Reply #542 on: 04/03/2017 10:02 PM »
This debate is not a matter of the "right" vs. the "wrong" way to define "planet".

More accurate to say 'which group of celestial objects to assign the label 'planet' to'. There is no right and wrong way to decide that - at least scientifically - but a decision had to be made, and it was!

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It truly is a matter of two different points of view about what is the more useful approach.

I don't think usefulness had or has anything to do with it. I have yet to see any classification scheme claimed to be more 'useful' that cannot simply be re-labelled to have the same eight celestial objects be the only planets in the solar system.

'Usefulness' is just another rationalisation made to justify personal preferences motivated by other reasons.

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The IAU definition is more useful to the dynamicist. The geophysical definition is more useful to the geophysicist.

Neither makes any difference at all. What is more or less useful is a classification scheme with an appropriate structure. The precise labels are neither here nor there.

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Neither definition would inhibit the other point of view from conducting their research ... although it does impact the language used to communicate in their field.

True.

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And then there is pedagogy.  From an instructional point of view I prefer the geophysical definition with dynamical classes and composition classes.

Another rationalisation to produce the desired result.

You can create a classification scheme by first dividing the relevant set of celestial objects dynamically and then sub-dividing them geophysically, or you can first divide them geophysically and sub-divide them dynamically. And there's many different ways to do both. Then you can decide which labels to give which group of objects. I have yet to see any evidence that either way of producing a classification scheme is intrinsically preferable from an instructional point of view.

Offline Star One

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Pluto-Planet debate discussions
« Reply #543 on: 04/28/2017 08:58 PM »
Distant Dwarf Planet DeeDee Stirs Up the Pluto Planethood Debate

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"What it's really showing is the diversity of planets in our solar system,” said Runyon of the DeeDee news, “and giving us a better understanding of planets in the rest of the galaxy.”

"DeeDee is almost certainly made out of ices — water ices, methane, and carbon dioxide — which is similar to what Pluto is made of," he added. "These are very soft materials, compared with rocky silicate. It's more easily pulled into a sphere than rock or metal."

Adding more fodder to the debate over the definition, when the New Horizons spacecraft flew by Pluto in 2015, it unveiled a world of surprising complexity, ranging from mountainous areas to vast nitrogen-ice lakes.

"We call Pluto a 'dwarf' planet, but it's just an adjective for 'planet,’” Runyon said. “It's still a planet, and that's where we take umbrage with the IAU.”

"Astronomers aren't experts in planetary science, and they basically passed a bunch of B.S. off on the public back in 2006 with a planet classification so flawed that it rules the Earth out as a planet, too," Stern remarked in 2016. "A week later, hundreds of planetary scientists, more people than at the IAU vote, signed a petition that rejects the new definition. If you go to planetary science meetings and hear technical talks on Pluto, you will hear experts calling it a planet every day."

http://www.livescience.com/58842-dwarf-planet-deedee-stirs-up-pluto-planethood-debate.html
« Last Edit: 04/28/2017 08:59 PM by Star One »

Offline CuddlyRocket

Re: Pluto-Planet debate discussions
« Reply #544 on: 04/29/2017 01:48 AM »
Distant Dwarf Planet DeeDee Stirs Up the Pluto Planethood Debate

A more accurate title would be 'Usual suspects use DeeDee to try to stir up the Pluto planethood debate with the aid of a clickbait-seeking website'! :)

Offline Star One

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Re: Pluto-Planet debate discussions
« Reply #545 on: 04/29/2017 08:43 AM »
Distant Dwarf Planet DeeDee Stirs Up the Pluto Planethood Debate

A more accurate title would be 'Usual suspects use DeeDee to try to stir up the Pluto planethood debate with the aid of a clickbait-seeking website'! :)

Well I did find the link on Alan Stern's Twitter feed, make of that what you will.

Offline K-P

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Re: Pluto-Planet debate discussions
« Reply #546 on: 05/07/2017 06:28 PM »
Stern really has some issues...

http://nasawatch.com/archives/2017/05/planet-9-sour-g.html#comments

I sincerely hope Brown stays above this BS and continues to do exactly what he has done so far:
making observations to put more nails in that Planet Pluto -coffin.

Online IanThePineapple

Re: Pluto-Planet debate discussions
« Reply #547 on: 05/07/2017 06:36 PM »
Calm down guys

Offline Nomadd

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Re: Pluto-Planet debate discussions
« Reply #548 on: 05/07/2017 06:45 PM »
 I'm still waiting for anyone to explain why Pluto and Charon aren't a binary, dwarf or not.

Offline baldusi

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Re: Pluto-Planet debate discussions
« Reply #549 on: 05/07/2017 07:31 PM »
I'm still waiting for anyone to explain why Pluto and Charon aren't a binary, dwarf or not.

From my limited understanding, they didn't wanted to get into the issues of defining binary planets or dwarf planets or what not. My guess is that if Planet 9 is discovered to be a real thing, they will put that and the binary issues all on the table. Meanwhile, they will coast until they have much better information.

Offline mikelepage

Re: Pluto-Planet debate discussions
« Reply #550 on: 05/08/2017 02:23 PM »
I'm still waiting for anyone to explain why Pluto and Charon aren't a binary, dwarf or not.

From my limited understanding, they didn't wanted to get into the issues of defining binary planets or dwarf planets or what not. My guess is that if Planet 9 is discovered to be a real thing, they will put that and the binary issues all on the table. Meanwhile, they will coast until they have much better information.

Suppose for the sake of argument that (Batygin's / Brown's) Planet 9 turns out to be a binary, with a "moon" the size of Earth.  If the orbit of said moon was elliptical enough, tidal heating might even lead to constant Io-like volcanos that would keep it warm enough to support liquid water (on the surface), with a Titan-like stratosphere tall enough to maintain decent surface pressure.  One could walk outside on a planetary surface in Earth-like gravity, perhaps needing only warm clothing and a gas mask.

Now suppose that scenario isn't, in fact, Planet 9, but an ice-giant/Earth-mass binary free-floating among the stars.  Something that could support non-photosynthetic life as we know it, minus a sun.  (Moot point: for all intents and purposes, Planet 9 lacks a sun anyway).  As far as I know, there could be millions or more of these in the galaxy.

Kinda renders planet/not-a-planet debates a bit meaningless doesn't it?

How about biggest>smallest:
Gas giant
Ice giant
Differentiated globe,
Undifferentiated globe,
Small body

Keep whether something is a moon/binary/primary as a separate descriptor.


Offline K-P

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Re: Pluto-Planet debate discussions
« Reply #551 on: 05/08/2017 02:43 PM »
"Your definitions are just fine...

as long as Pluto remains a planet...!"

As I would expect some people to say.
:)

As a side note, I would rather be exploring with my team a first ever object of some "category" than the last one of some other... but hey, what do I know about PR and fame for the history books.


Offline CuddlyRocket

Re: Pluto-Planet debate discussions
« Reply #552 on: 05/09/2017 11:34 PM »
I'm still waiting for anyone to explain why Pluto and Charon aren't a binary, dwarf or not.

From my limited understanding, they didn't wanted to get into the issues of defining binary planets or dwarf planets or what not.

Dwarf planets are defined. The problem with binary dwarf planets (or planets, for that matter) is whether or not the individual objects orbit the Sun, as the definition requires. (Interestingly, the IAU General Assembly specifically resolved that Pluto is a dwarf planet!)

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My guess is that if Planet 9 is discovered to be a real thing, they will put that and the binary issues all on the table. Meanwhile, they will coast until they have much better information.

It depends what they find. If it smoothly fits in to the current classification scheme then nothing will happen. The IAU will probably not revisit this question until either it can rubber-stamp a scientific consensus on a change or somebody discovers something that requires a clarification (what we might call 'an Eris event'!).

Kinda renders planet/not-a-planet debates a bit meaningless doesn't it?

Not really, as the debate centres around the 'clearing the neighbourhood' criteria.

As a side note, I would rather be exploring with my team a first ever object of some "category" than the last one of some other... but hey, what do I know about PR and fame for the history books.

I'd agree, but it's still better to explore the last one - and thereby 'complete the set' - than to explore one of the ones inbetween!

This was part of the PR for New Horizons. Unfortunately, en route Eris was discovered and we all know what happened next - they couldn't even claim the first dwarf planet exploration, as Dawn reached Ceres first!

Offline baldusi

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Re: Pluto-Planet debate discussions
« Reply #553 on: 05/10/2017 01:43 PM »
I'm still waiting for anyone to explain why Pluto and Charon aren't a binary, dwarf or not.

From my limited understanding, they didn't wanted to get into the issues of defining binary planets or dwarf planets or what not.

Dwarf planets are defined. The problem with binary dwarf planets (or planets, for that matter) is whether or not the individual objects orbit the Sun, as the definition requires. (Interestingly, the IAU General Assembly specifically resolved that Pluto is a dwarf planet!)

I didn't used Oxford comma, I meant binary planet, binary dwarf planet or binary whatnot (except binary star). Of course that dwarf planet is defined.

Offline CuddlyRocket

Re: Pluto-Planet debate discussions
« Reply #554 on: 06/23/2017 02:32 AM »
Cross-posting from the Dwarf planet discovery hints at a hidden Super Earth in solar system thread to deal with the planet definition aspects:

Planet ten or nine depending on which way you count all these proposed planets we seem to have missed. Though whether this is another planet gets caught up in how we define planets now.

The curious case of the warped Kuiper Belt

https://astronomynow.com/2017/06/22/the-curious-case-of-the-warped-kuiper-belt/

Here's the original press release.

https://uanews.arizona.edu/story/ua-scientists-and-curious-case-warped-kuiper-belt
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Because a planet, by definition, has to have cleared its orbit of minor planets such as KBOs, the authors refer to the hypothetical mass as a planetary mass object.

It actually has to have "cleared the neighbourhood around its orbit", but either way this is not defined (except by necessary implication from the fact that the IAU has declared some bodies to be planets and others not to be so!). But if it's not a planet, then it's a dwarf planet, so why not say so? Perhaps in the paper itself they're unsure as to its status?

Soter proposed a planet would be an object 100 times more massive than everything else in its orbital zone. The entire Kuiper belt is estimated to mass 40-100% that of Mars, but the vast majority of this would not be in the hypothesised object's orbital zone. However, Eris, which is in this zone, was itself previously estimated to have a mass 0.1 times that of everything else in its orbital zone, implying 'everything else' has a mass about 0.3 that of Mars. All of which goes to show that Soter's test is not so easy to apply in practice!

The Stern-Levinson parameter for distinguishing between 'überplanets' ("dynamically important enough to have cleared its neighboring planetesimals") and 'unterplanets' would make a Mars-sized body an 'überplanet' up to about 146 AU, suggesting this body would be an überplanet, or a planet, as the IAU would term it. However, Margot's planetary discriminant would make a Mars-sized body a planet up to about 53 AU suggesting this body would be a dwarf planet! So, if this proposed body was demonstrated to exist, the IAU would probably be forced to have to define 'cleared the neighbourhood around its orbit' more precisely!

Offline Paul451

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Re: Pluto-Planet debate discussions
« Reply #555 on: 06/23/2017 04:08 AM »
Cross-posting from the Dwarf planet discovery hints at a hidden Super Earth in solar system thread to deal with the planet definition aspects:
[...]
The Stern-Levinson parameter for distinguishing between 'überplanets' ("dynamically important enough to have cleared its neighboring planetesimals") and 'unterplanets' would make a Mars-sized body an 'überplanet' up to about 146 AU, suggesting this body would be an überplanet, or a planet, as the IAU would term it. However, Margot's planetary discriminant would make a Mars-sized body a planet up to about 53 AU suggesting this body would be a dwarf planet! So, if this proposed body was demonstrated to exist, the IAU would probably be forced to have to define 'cleared the neighbourhood around its orbit' more precisely!

Not necessarily. Given the huge gap between planets and non-planets in all the planetary-determinant methods suggested so far, it's unlikely that a post-Pluto 9th planet will be anywhere near the line. If it is a "super-Earth", there's certainly no issue.

And after all, if it is real, then the only reason it was discovered was because it gravitationally dominated its region, which is the whole point of differentiating between planets and non-planets. Hence if a Mars-sized mass has had the effect on the other KBOs that has been observed, then yes, those like Margot can revise their planetary-determinants to reflect that. (It would be a very useful finding for that reason alone.) Which is why the official definition of an IAU-planet shouldn't pick a specific determinant yet. (Although they should replace Stern's misleading "cleared the neighbourhood" phrase.)

Offline Bynaus

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Re: Pluto-Planet debate discussions
« Reply #556 on: 06/23/2017 05:01 AM »
Nevertheless, if we find a Mars-sized object out there, then regardless of its distance, it is going to be difficult to convince the public that it should NOT be a planet. Especially if we know of no other, similar object on a similar orbit. We all have a mental picture of what a planet should be, but perhaps gravitational dominance is not capturing this correctly - it is more about uniqueness, about being the single largest object in its neighborhood.

Offline Star One

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Re: Pluto-Planet debate discussions
« Reply #557 on: 06/23/2017 07:33 AM »
Talking of Pluto it interested me that Alan Stern re-tweeted this news but then I believe he has been advocating an object like this in the Kuiper belt for some time.
« Last Edit: 06/23/2017 07:34 AM by Star One »

Offline Paul451

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Re: Pluto-Planet debate discussions
« Reply #558 on: 06/23/2017 07:39 AM »
We all have a mental picture of what a planet should be

We had a mental picture of what the celestial sphere was, what matter was, what the aether was, but we adapted. Once we thought light was made of particles, then we knew it was made of waves, then we got wavelike-particles and QM. We adapted to each change.

Once upon a time, "planet" meant wandering star (because we understood neither planets, nor stars). Then we thought it meant objects like Earth (read pre- and Golden Era SF). Then it meant the range of properties of the actual planets of the solar system, as we understood more about gas-giants and airless bodies. As we learn about exoplanets, our mental model needs to twist and expand again, especially when dealing with extremes like ultra low-density super-hot planets with metal atmospheres, etc. Meanwhile, as it expands in that direction, the IAU definition limits it again, but in different ways. We will adapt.

[Edit: I mean, we know that Jupiter is a planet, because we've been taught it is. Ask people if Jupiter is a planet, and they'll say yes. But if you could pull that "mental picture of what a planet should be" out of people's brains, would a large gas-giant really fit that picture? Stern plays on people's mental picture, but if we really used that picture to define "planet", then Titan would be a planet but Jupiter and Saturn would need to be called something else. Something between "planets" and brown-dwarfs.]
« Last Edit: 06/23/2017 07:46 AM by Paul451 »

Offline Star One

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Re: Pluto-Planet debate discussions
« Reply #559 on: 06/23/2017 07:45 AM »
Looking online it seems the public has spoken and this is already being called the tenth planet. Even though it's really planet nine and if they find Mike Brown's one that will be planet ten of course.

Being as Pluto seems to be remarkable active for its size heck knows what a Mars size object will have going on.
« Last Edit: 06/23/2017 07:47 AM by Star One »

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