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Pluto is a planet again..



 
 
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  #41  
Old March 10th 07, 08:41 AM posted to sci.astro.amateur
Paul Schlyter[_2_]
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Posts: 893
Default Pluto is a planet again..

In article ,
Chris L Peterson wrote:

IMO the decision to rigorously define "planet" was a solution looking
for a problem (and in fact, created its own problems).


The IAU definition of "planet" wasn't that rigorous really.

First, it doesn't specify how large a deviation from the hydrostatic
equilibirion shape is allowed for a body to still be considered a
"planet". Some deviation is obviously allowed, or else the mountain
ranges of the Earth would disqualify the Earth from being a planet.

Second, the phrase "cleared its neighbourhood" is a quite fuzzy
phrase, open for interpretation.

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e-mail: pausch at stockholm dot bostream dot se
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  #42  
Old March 10th 07, 10:10 AM posted to sci.astro.amateur
oriel36
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Posts: 1,189
Default Pluto is a planet again..

On Mar 9, 11:00 pm, Greg Crinklaw
wrote:
Chris L Peterson wrote:
I understand the concept. I just think it fails miserably. There's no
doubt in my mind that Pluto is a planet, as is Ceres and a number of
other objects.


Ah, ok, I see now. Why didn't you just come out and say from the start
that you were among those disgruntled who cling to "Pluto is a planet?"

You have neatly cut the question's significance down to where personal
opinion can become of prime importance. Nicely done.

Obviously there can be no further productive argument as this isn't a
question of science, but rather of strongly held personal preference.
personal preference.

I really don't personally care one way or another. My interest is to
find a reasonable way to keep the opinionated amongst us from squabbling
forever! Hopefully it will be those like me who actually make the
decision.


Funny,funny,funny !.

You could not a more comedic script than that surrounding the Pluto
episode. Very early on one guy got in right and spotted the
absurdity of it all and it becomes difficult to take you lot
seriously after that

..It was those like you who made the decision !

http://groups.google.com/group/sci.a...6af3010?hl=en&

The same pseudo-authority that sanctions constellational astrology and
its 'predictive' nature are the same numbskulls who publically made
idiots of themselves last year in regard to planetary 'definition'.You
simply could not make up this comedy if you tried and the way they are
now stuck between a meaningless wordplay and the physical structure
and motion of objects around the Sun.







Clear skies,
Greg

--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools: http://www.skyhound.com/cs.html
Observing:http://www.skyhound.com/sh/skyhound.html
Comets: http://www.skyhound.com/sh/comets.html

To reply take out your eye



  #43  
Old March 10th 07, 04:11 PM posted to sci.astro.amateur
Starboard
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Posts: 126
Default Pluto is a planet again..

Greg wrote:
You know, Chris, we've had this discussion what? four times now?
every time you trot out these half-baked ideas and I patiently explain
that there is a real problem that can't simply be ignored and how that
problem is nicely solved by the new definition.


Chris wrote:
No doubt we'll have it again (although I'd never stoop to calling your
opinion "half-baked"). You can explain it all you want- I simply don't
see that there ever was a problem (although I think there is now).


Greg wrote:
Ah, ok, I see now. Why didn't you just come out and say from the start
that you were among those disgruntled who cling to "Pluto is a planet?"


Chris wrote:
No, I'm just recognizing that it and many other objects are planets.


Chris:
Would you just shut up and quit with your disgruntled, half baked
ideas! Greg has spoken.

Greg:
You look childish (and your arguments futile) when you start
"trotting" ad hominem attacks; especially towards people like Chris,
who are among the brightest of those who post here.

You don't have a monopoly on what ideas make up the argument for a
planet.

Errol

  #44  
Old March 10th 07, 06:05 PM posted to sci.astro.amateur
Richard Jarnagin
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Posts: 41
Default Pluto is a planet again..


"Paul Schlyter" wrote in message
...
In article ,
Chris L Peterson wrote:

IMO the decision to rigorously define "planet" was a solution looking
for a problem (and in fact, created its own problems).


The IAU definition of "planet" wasn't that rigorous really.

First, it doesn't specify how large a deviation from the hydrostatic
equilibirion shape is allowed for a body to still be considered a
"planet". Some deviation is obviously allowed, or else the mountain
ranges of the Earth would disqualify the Earth from being a planet.

Second, the phrase "cleared its neighbourhood" is a quite fuzzy
phrase, open for interpretation.



And both of these effects are a result of mass. Initially it made no sense
to me why they didn't just define a planet as a body of mass "P".
Arbitrary? Yes. Fuzzy? No. It seems they could have used their existing
definition to do the calculations to initially define "P", then fine tune it
over time. The problem is that to define "P", they would have to define
"spherical" and "neighborhood". I don't know, maybe fuzziness isn't so bad.
It seems crazy that you could have one body with mass "P" being a planet and
another body with mass "P - 10^3 kg" not being a planet.

Richard


  #45  
Old March 10th 07, 06:11 PM posted to sci.astro.amateur
Richard Jarnagin
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Posts: 41
Default Pluto is a planet again..

"Richard Jarnagin" wrote in message
link.net...

And both of these effects are a result of mass. Initially it made no

sense
to me why they didn't just define a planet as a body of mass "P".
Arbitrary? Yes. Fuzzy? No. It seems they could have used their

existing
definition to do the calculations to initially define "P", then fine tune

it
over time. The problem is that to define "P", they would have to define
"spherical" and "neighborhood". I don't know, maybe fuzziness isn't so

bad.
It seems crazy that you could have one body with mass "P" being a planet

and
another body with mass "P - 10^3 kg" not being a planet.

Richard


Obviously I'm just speaking of the lower limit here.

RJ


  #46  
Old March 10th 07, 06:28 PM posted to sci.astro.amateur
Richard Jarnagin
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Posts: 41
Default Pluto is a planet again..


"Chris L Peterson" wrote in message
...
On Fri, 09 Mar 2007 13:54:52 -0700, Greg Crinklaw
wrote:


snip


I'd call them both planets. I'd distinguish between them by
subclassifications. In practice, that's how it's done anyway. The formal
definition of "planet" hasn't changed a thing, except for adding a bit
of confusion.


snip


And the difference between a major planet and a minor planet would be?

Richard


  #47  
Old March 10th 07, 06:52 PM posted to sci.astro.amateur
Chris L Peterson
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Posts: 10,007
Default Pluto is a planet again..

On Sat, 10 Mar 2007 17:28:57 GMT, "Richard Jarnagin"
wrote:

And the difference between a major planet and a minor planet would be?


I'm not sure that's a very useful classification given that planets vary
widely and continuously in size/mass. Perhaps this would be a good term
to distinguish between bodies that have enough mass to collapse to
spheres, and those that don't? Of course, there will be occasional
objects that are on the edge, and could be placed in either category. I
think the idea of major or minor planets falls into that area Brian
introduced: classes designed for presenting ideas to the lay public. I
don't see much scientific value.

Scientifically useful classifications are more likely to be based on
composition, location, or formation history than on size or mass (or
whether they happen to have cleared their orbit of other material, which
is truly a useless consideration).

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
  #48  
Old March 10th 07, 07:42 PM posted to sci.astro.amateur
Richard Jarnagin
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Posts: 41
Default Pluto is a planet again..


"Chris L Peterson" wrote in message
...
On Sat, 10 Mar 2007 17:28:57 GMT, "Richard Jarnagin"
wrote:

And the difference between a major planet and a minor planet would be?


I'm not sure that's a very useful classification given that planets vary
widely and continuously in size/mass. Perhaps this would be a good term
to distinguish between bodies that have enough mass to collapse to
spheres, and those that don't? Of course, there will be occasional
objects that are on the edge, and could be placed in either category. I
think the idea of major or minor planets falls into that area Brian
introduced: classes designed for presenting ideas to the lay public. I
don't see much scientific value.

Scientifically useful classifications are more likely to be based on
composition, location, or formation history than on size or mass (or
whether they happen to have cleared their orbit of other material, which
is truly a useless consideration).



Agreed. The point that I was trying to make is that when defining
subcategories, you are really just regressing one step from defining
planets. There will still be fuzziness at some of the boundaries.

Richard


  #49  
Old March 10th 07, 07:51 PM posted to sci.astro.amateur
Chris L Peterson
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Posts: 10,007
Default Pluto is a planet again..

On Sat, 10 Mar 2007 18:42:34 GMT, "Richard Jarnagin"
wrote:

Agreed. The point that I was trying to make is that when defining
subcategories, you are really just regressing one step from defining
planets. There will still be fuzziness at some of the boundaries.


I don't think that's universally true. There are categories where there
is probably never going to be any fuzziness (terrestrial versus gas
giant, terrestrial versus KBO, etc). This is true outside of astronomy
as well. Some classifications are very clearly suggested by natural
divisions, others are more arbitrary points along continua. It isn't
clear to me that the top level classification ("planet", although I'd
prefer a different term) needs to be fuzzy at its boundaries- although
there's no guarantee that we won't eventually stumble across something
that is hard to place.

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
  #50  
Old March 10th 07, 08:23 PM posted to sci.astro.amateur
Richard Jarnagin
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Posts: 41
Default Pluto is a planet again..

"Chris L Peterson" wrote in message
...
On Sat, 10 Mar 2007 18:42:34 GMT, "Richard Jarnagin"
wrote:

Agreed. The point that I was trying to make is that when defining
subcategories, you are really just regressing one step from defining
planets. There will still be fuzziness at some of the boundaries.


I don't think that's universally true. There are categories where there
is probably never going to be any fuzziness (terrestrial versus gas
giant, terrestrial versus KBO, etc). This is true outside of astronomy
as well. Some classifications are very clearly suggested by natural
divisions, others are more arbitrary points along continua. It isn't
clear to me that the top level classification ("planet", although I'd
prefer a different term) needs to be fuzzy at its boundaries- although
there's no guarantee that we won't eventually stumble across something
that is hard to place.



Obviously it's not universally true. That's why I said "some" of the
boundaries. As for it not being clear to you the definition of a planet
needs to be fuzzy at its boundaries, it seems to me that depends on what one
chooses as a definiton. We could choose a lower and upper mass (or size)
limit and have no fuzziness at all. Or we could have something like the IAU
definition and have considerable fuzziness. Or we could come up with
something in between and have an intermediate amount of fuzziness. But to
eliminate fuzziness completely, it appears one has to introduce
arbitrariness into the definition.

Richard


 




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