[Dªn]

See here's my problem with declassifying Pluto.

To anybody whose an astronomist, yeah maybe it's not a planet. But the billions of people around the world who've grown up with it being a planet, learnt any number of silly rhymes to remember the planets, watch any silly school kid science program, it is a planet. They don't care whether it's big enough or not, it's just a symbol. It's a symbol of what the Universe is, and in what we live in.

It's so far away they couldn't give a toss what size, shape, weight, climate it is. It's just there, it's something that exists, it's a planet, you get told it is all the way through your education, by everybody. Now it's not aplanet, so people question what else is. What else isn't true?
What's next? The moon is a planet?
It's not a good state of affairs to be in my friend!
I mean, what if they suddenly discover Gravity doesn't exist? it was a figment of our imagination and we just all float off? That would be scary! (and I appreciate would never happen, not unless we live inside a Matrix, but that's also never going to happen)

But see here's my linguistic point of view. A word is a symbol for something, it's just something that's completely arbitrary and random. You define a planet by what makes it a planet, now for an astronomist what defines a planet is a set of scientific regulations and mathematics and whatever else, BUT for the majority of people that isn't what defines a planet. What defines a "planet" is the planets themselves, that's what the word means, and that includes Pluto. You can decide that Pluto isn't a planet, but to people who actually use the world, they're still going to refer to it with Pluto in it. Except it'll probably be followed by a Bill Bryson moment with "Well actually.....

(p.s I'm waiting for Elaine to disagree with my linguistic view too!)

[Michael Merritt]

You're reading an obsolete definition (or one that never really existed since there never has been an "official" definition. Here's the definition in the whole:

The IAU...resolves that planets and other bodies in our Solar System be defined into three distinct categories in the following way:

(1) A "planet" [1] is a celestial body that: (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and © has cleared the neighbourhood around its orbit.

(2) A "dwarf planet" is a celestial body that: (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape [2], © has not cleared the neighbourhood around its orbit, and (d) is not a satellite.

(3) All other objects [3] except satellites orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".

Footnotes:

[1] The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
[2] An IAU process will be established to assign borderline objects into either "dwarf planet" and other categories.
[3] These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies.

The IAU further resolves:

Pluto is a "dwarf planet" by the above definition and is recognized as the prototype of a new category of trans-Neptunian objects.

--Wikipedia

What they don't really cover is the whole "cleared the neighborhood" language, though hopefully that'll be fleshed out soon. It appears, from my reading, to concern whether or not an object crosses the orbit of another object, like Pluto does with Neptune. However, I don't think Ceres crosses the orbit of anything, though I may be incorrect, it being in the astroid field and all.

[blush]

Who the hell's making money from it?

[Dªn]

Who the hell's making money from it?

People who have to reprint all their text books!

[Adon]

I'd think it'd just be easier to learn the names and order of the planets now, with one less, and the 4 inner ones being rock, 4 outer ones being gas (and not having Pluto as an exception). Besides, this is science. What I think is silly is someone rejecting new definitions simply because they've been taught otherwise in their childhood. If everyone thought like that, there'd be no progress.

People who have to reprint all their text books!

Astronomy changes all the time (new discoveries, etc.), so the textbooks need to be replaced anyway.

[blush]

Yeah. Let's quit making any scientific advances in other arenas as well, God only knows how many textbook revisions THAT would require! Or history... dear lord let's just stop doing ANYTHING before we need new history texts! Augh!!

[Brendon Koz]

I hated all history except for Native American stuff in school, so.... Here here!

We can keep all the science stuff updated though. That's ok.

[Luke]

The IAU...resolves that planets and other bodies in our Solar System be defined into three distinct categories in the following way:

(1) A "planet" [1] is a celestial body that: (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and © has cleared the neighbourhood around its orbit.

(2) A "dwarf planet" is a celestial body that: (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape [2], © has not cleared the neighbourhood around its orbit, and (d) is not a satellite.

(3) All other objects [3] except satellites orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".

Footnotes:

[1] The eight planets are: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.
[2] An IAU process will be established to assign borderline objects into either "dwarf planet" and other categories.
[3] These currently include most of the Solar System asteroids, most Trans-Neptunian Objects (TNOs), comets, and other small bodies.

The IAU further resolves:

Pluto is a "dwarf planet" by the above definition and is recognized as the prototype of a new category of trans-Neptunian objects.

See this is where I find this definition of a planet totally ludicrous.... It isn't a planet because it's orbit is inhabited by different objects like asteroids... what? By this definition Saturn shouldn't be a planet either. It's rings are made of up smaller objects that orbit around it. Sure it's big enough to pull things into it's orbit, but objects are still in the neighborhood of it's orbit. Pluto just happens to not be big enough to do that, but rather pass through foreign objects.....

I've never heard of Ceres, or any "planets" that were dismissed in the past..... But that's my point. You all of a sudden say it's not a planet, and then what happens in the future? People like me, in the future, don't even know it exists because it's not important enough to mark on a chart.

As far as the asteroid belt, that could have very well at one point been a planet... Maybe some big object collided with it and broke it into a trillion pieces.

[Stephen]

Yeah. Let's quit making any scientific advances in other arenas as well, God only knows how many textbook revisions THAT would require! Or history... dear lord let's just stop doing ANYTHING before we need new history texts! Augh!!

Thank you! That is exactly what I was thinking.

Luke, what on earth are you on about with Saturn, the ring isn't "in its neighbourhood" the ring is in orbit around Saturn, just like the moon is in orbit around earth.

I believe the reason Pluto isn't "cleared" is because it crosses over Neptunes orbit.

As for the asteroid belt, yes it might have been a planet at one point but it isn't anymore so I don't see what that has to do with anything.

[Rikki]

http://news.bbc.co.u.../5283956.stm?ls

[CTerry]

I've never heard of Ceres, or any "planets" that were dismissed in the past..... But that's my point. You all of a sudden say it's not a planet, and then what happens in the future? People like me, in the future, don't even know it exists because it's not important enough to mark on a chart.

As far as the asteroid belt, that could have very well at one point been a planet... Maybe some big object collided with it and broke it into a trillion pieces.

First of all why does it matter whether people have heard of Pluto at all? Its a tiny chunk of rock millions of miles away which has absolutely no worth whatsoever. Its only claim to fame was that it was a 'planet'. Whatever a 'planet' is.

As for the asteroid belt, that's most certainly debris left over from the formation of the solar system, that was unable to turn into a planet because of interference from Jupiter's gravity.

[Vortex-Steve]

Surely that is the old definition... And no where has anyone said for a planet to be a planet do we have to see it or for it to support life!

New definition:

* it must be in orbit around the Sun
* it must be large enough that it takes on a nearly round shape
* it has cleared its orbit of other objects

Pluto apparently fails on that last one because it's orbit crosses with Neptune... however surely that also means Neptune hasn't cleared it's orbit!

[Dªn]

New definition:
Pluto apparently fails on that last one because it's orbit crosses with Neptune... however surely that also means Neptune hasn't cleared it's orbit!

Still, reading Rikki's article a leading NASA scientist says that definition can't be applied to some of the planets in our Solar system, including Earth.

[Debbie]

What about Mickey Mouse? Is he no longer a Mouse? He and Pluto went hand in hand!

[Michael Merritt]

I definitely agree the definition needs to be more specific, but it appears that they have two options:

1. Use the first definition and include Pluto and potentially hundreds of other findings.

2. Use this definition or something equivalent and lose Pluto.

[Dªn]

I definitely agree the definition needs to be more specific, but it appears that they have two options:

1. Use the first definition and include Pluto and potentially hundreds of other findings.

2. Use this definition or something equivalent and lose Pluto.

Either way it should be a consensus, and not a decision based on a vote of 4% of the astronomers.

[Steve]

Either way it should be a consensus, and not a decision based on a vote of 4% of the astronomers.

Advancement, I'm all for Elaine, just not based on some elite scientists who think they speak on behalf of everyone in general. I'm all for advancement of the human race, but please don't think that a small group speak for everyone. And I should clarify that if I was around in the naming of the planets etc, then I would be just as concerned then about a small group of people deciding as I am now. It's not advancement I'm upset about, it's the people who have been decided to make the choice on behalf of us as a whole.

In a world that has spawned freedom of speech, you can cleary see the oxymorons on daily basis.

[blush]

Yes, but they're astronomers. It's their business to be experts in the field, since everyone can't know everything. You relied on "some elite scientists" to learn everything you learned in high school science class.

[CTerry]

Yes, but they're astronomers. It's their business to be experts in the field, since everyone can't know everything. You relied on "some elite scientists" to learn everything you learned in high school science class.

I would tend to agree, especially considering the nature of scientific research. Scientists need a consensus based definition to use in their research, else it just bogs down scientific debate.

[Antony]

I would suggest, as planet is a colloqually used word we can create a new phrase to describe significant space bodies, and if we must, a new acronym to go with it!