Slashdot Mirror
Why the Word 'Planet' Will Never Be Defined
eldavojohn writes "What makes a planet a planet? Slashdot covered the great debate about whether or not Pluto qualified and Space.com now has up an article explaining why we'll never have the term 'planet' defined to a point that everyone can agree on. Divisions in the scientific community currently stand over whether or not it has to be in orbit around a star, the dynamics of the body in question and apparently the country you come from plays a part in it too. Some feel the United States is the dominant deciding factor on the definition but the IAU has not turned to democratizing the definition yet." From the article: "In the broadest terms, a planet could be thought of as anything from an 800-kilometer-wide (500-mile-wide) round rock orbiting a dead star to a colossal gas ball floating alone in space."
This article has some good background info. Also see the article on the redefinition.
Floating mass of sh*t bigger than the moon that isn't on fire, but that is orbiting some floating mass of sh*t that is, in fact, on fire.
Luck favors the prepared, darling.
Some feel the United States is the dominant deciding factor on the definition but the IAU has not turned to democratizing the definition yet."
Lets see now.. democratically deciding a definition? hmm...
At any rate, the USA being the dominant deciding factor might make some sense seeing how they also invest a lot into the actual science part of this, but if the IAU did turn to democratize the decision, then the USA can't be the deciding factor seeing how they are a mere 4% of the world population....
actually called an "Air Biscut"....never heard it described as a planet before, but, I suppose if it really were that colassal....
A goal is a dream with a deadline
I would define a Planet as: A relative of Captain Planet
'A series of gaming sites ran by counter strike kiddies who think that half life 2 is going to be better than far cry.'. Not sure I quite get that 100%, but you can't argue with the wisdom of the internet.
Don't see what's so hard about that ...
I hear there's rumors on the Slashdots
The parent post is spam. Please do not click it. It redirects to http://31337.pl/
Layne
They say that Pluto's
Not quite a planet.
These KBOs
Are goofy, dammit.
Burma Shave.
From Wikipedia:
In ancient times, Grecian astronomers noted how certain lights moved across the sky in relation to the other stars. These objects were believed to orbit the Earth, which was considered to be stationary. The "wandering" lights were called planets, a Greek term meaning "wanderer".
****
Why not just stick to this original definition? If it "wanders" among the stationary celestial lights and casts light visible to the naked eye, it's a planet.
Everything else can be labeled SAO "speculative astronomical object."
Read any good sonnets lately?
Anything equal to or greater than the size of Marvin's brain.
I don't get the problem? First, start off with the idea that a planet must be orbiting a star... similar to how moons are defined as orbiting a planet. Even if they are orbiting a pulsar (dead star) they are still planets, but not if they are orbiting a failed star (brown dwarf). If you find a brown dwarf with satellites call that something else. Then the article mentions the possibility of having planet sized objects orbiting each other the same way binary stars orbit one another. OK, make that a seperate category. After that just define the mass need to be called a planet and be done with it. I'm sure there are plenty of other scenarios out there that need to be defined, but the basic rules don't seem difficult to set up.
We need to simplify these definitions for the greater good of humanity...
Here's my suggestion...
satellite = thing
planet = thing+
star = thing ++
comet/asteroid = thing-
spacedust = thing--
Unfortunately, as we do not have the minimum 9 planets required to qualify as a class A solar system, we will have to wait for a trial date with a municipal court first.
Have gnu, will travel.
"Anything which is roughly spherical under its own gravity, in a more-or-less circular orbit around the sun, and its orbital path isn't shared with an object larger than itself."
How about "It is a planet if Galactus would consume it" ?
The definition of the word "planet" will matter in the future when it comes to mining rights...as in "hey, you have to pay a different amount of tax when you're mining a planet vs. an asteroid vs. a planetoidy thing."
Bill Clinton: Pimp we can believe in. - The Shirt!!!
The real question is, why do we need a precise, "official" definition of "planet"? Astronomers and other scientists aren't going to make scientific decisions based on it -- it's not like it matters whether Pluto is officially a planet according to the IAU when an astronomer decides to study Pluto. "Oh, the IAU says it's not a planet, therefore it's not interesting enough to study."
In general, the whole point of category words like "planet" is so that I can point at an object and say, "That's a planet," and you immediately have some basic information about it, because we agree on what "planet" means. But if we're scientists, studying it (or deciding whether to study it), then we need a whole lot more info. Gas giant? Small, terrestrial rock? Iceball? Distance from star? Eccentricity of orbit? Etc. "Planet" doesn't tell you any of that.
Ultimately, the main reason to specify an "official" definition of "planet" is for the sake of deciding whether and how we want to encourage space travel, exploration, astronomy, and related sciences. To give an extreme example, if the definition of "planet" included any solid body primarily orbiting a star, there'd be millions of planets in every star system, and saying that NASA's going to go explore a planet would be meaningless. The public wouldn't care and wouldn't go out of its way to support it.
At the other extreme, limiting the planets to rocky or gaseous bodies at least the size of Mercury, orbiting a star, and having a very low orbital eccentricity, means that when you discover a body that only misses ONE of those criteria, the definition seems arbitrary and people will just ignore it. Imagine if we find a trans-Neptunian object that's the size of Mars, and is a rocky, terrestrial body like Mars, but merely has an eccentric orbit? Very few laypeople would accept that that's not a planet, mostly because laypeople's perception of a stellar body is based on its physical characteristics, not its orbital ones. If Earth was somehow flung out into space, orbiting nothing, it'd stop being a planet? (Well, we'd all be dead, but that's another issue.)
"Destroy science and religion. Science would re-emerge exactly the same; but not religion." - Penn Jillette, paraphrased
... so why not the IAU. Simply break planets down into different subclasses. Everyone knows that Earth is a Class M planet.
There's already a helpful classification guide to help them get started.
It's a problem with any discipline -- language is not exact.
What qualifies as meat? Does seafood count as meat? Not for Catholics.
What qualifies as a person? What about in utero? Maybe for manslaughter, but why not count that time for age restrictions?
What qualifies as blue? Is cyan blue enough? It depends on what you're using the category for.
Anyone who's tried to work on standardize terminology (eg, specialized thesauri, or even just a controlled vocabulary) will know that it is a long, exhasting process that takes years in some cases, and even then, is likely to change.
Planets are not a classical category, and will be subject to prototype effects.
Build it, and they will come^Hplain.
And it has nothing to do with the fact Americans have discovered only one object (in Sol System) that COULD, by much stretching and wigging with the definition classify as planet (Pluto), but shouldn't really.
And the fact that it's bleeding obvious to any European, (or unbiased American) that we have EIGHT planets, while it's (mostly) Americans who seem to be violently opposed to the idea of Pluto not being a planet is a mere coincidence.
planet := thing_in_space && !moon && !star && !comet && !black_hole && !white_dwarf && !satellite && !garbage && !deathstar
Piece of cake.
Planet = anything that was suggested as possibly existing by Lowell, even if it turns out only to be a fraction of the predicted size, so as to distract the world from the fact he was convinced there was an advanced civilisation on Mars.
Uranus is huge but its not a planet! :-)
Just ask the Intellectual Property Lawyers from Magrathea... I bet they have a clear definition.
A scientific definition may be hard to come by, however when the time comes a legal one sure won't be.
There can't be one definition because there are three classes of planets. Gas giants, rocky planets and icy planets. The big argument is whether to include icy planets but icy planets are closer to earth than gas giants so how do you include one but not the other? The sensible definition to come up with three classes and require them to orbit the sun to exclude moons and to have sufficent gravity for a roughly round shape, the Earth isn't perfectly round. What it would leave us with is four rocky planets, four gas giants and a similar number of icy planets. The Oort cloud gets tougher. Since they still orbit the sun it might be wise to come up with a fourth definition of outer planets for any Oort Cloud objects. One excuse for eliminating Pluto was it's eliptical orbit but most planets have eliptical orbits so that factor gets arbitary. Splitting the definition avoids demoting any planets and allows for new objects including some that may not fit well with the current definition.
"...a colossal gas ball floating alone in space." Ugh, that reminds me, I have to call my uncle.
One of the reasons the IAU tackled this issue at the last conference was politics - because the report from the Planet working group was leaked, the IAU felt they had to 'do something' fast because 'the press was watching'. They managed to make an entire mess of the process, including creating the redefinition 'rules' in a matter of days, and basically confusing the entire voting process...
I learned this from someone who was actually at the conference... and I was quite frankly appalled at they way they handled things.
Eric Aitala
Eric Aitala
www.f1m.com
Richard Feynman had something to say about this debate, though somewhat obliquely. The parentheticals below are my own.
"You can know the name of a bird (or a planet) in all the languages of the world, but when you're finished, you'll know absolutely nothing whatever about the bird (or planet)... So let's look at the bird ( or planet) and see what it's doing -- that's what counts. I learned very early the difference between knowing the name of something and knowing something."
The point here is that scientific knowledge (whether it be social, biological, or physical) is about explaining how things work (understanding processes) or why they are the way they are (understanding variation). Debate over essentialist categories like "planet," "species," "nation-state," etc. are, as one other person in this discussion has already mentioned, problems of language.
Interestingly, Wittgenstein might have a thing or two regarding this topic as well, especially in later work.
The first principle is that you must not fool yourself - and you are the easiest person to fool. -Richard Feynman
I remember on NPR some astronomer pointing out that they shouldn't have to define "Planet" until the Geologist define "Continent" After all why are Europe and Asia separate continents they are one land mass. Same with N. and S. American (at least until the panama canal). Actually I think some countries consider Europe and Asia one continent Eurasia. (or that may just be 1984)
We see almost as much variation in types of stars, yet we have a very clear definition of what a star is. The key is the ability to classify them. Stars are easy to see and catalog, direct observation can be performed by anyone with a modest telescope, so a classification system is easy when you have a catalog of millions(billions?). We've directly seen about 10 "planets", we've detected through indirect means an additional ~190 "planets". We don't yet have the technology to observe directly. Until we do, we will only detect the types of planets that can be detected indirectly. This means no huge catalog. No huge catalog means we can't create an accurate classification system. I believe that once we can directly observe a large variety of objects, a classification system can be created, and there is the definition.
The definition of "planet" is now based on a body's relationship to its surroundings, and as long as we're clear on that I don't see the problem. The same thing goes for "moon", "island", etc. Without water around it, it's not an island, it's a hill or a mountain.
We can have other terms to describe bodies that don't relate to their surroundings, but it's a nice, concise way to describe a body as a part of a solar system.
I rarely criticize things I don't care about.
I don't understand why we don't just call them all planets and then drop em into different classes of planets ala Star Trek. This way you can call them all planets still, pluto and whatnot will just fall into a different class of planet. What is the drawback to this? That we'll have more planets? big deal!
For a moment I thought the Death Star could be clasified as a planet but then recalled that it's only 120 kilometers in diameter which is much smaller than the moon...
Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. ~Albert Einstein
pluplussoon.
From the classical definition: does the Earth look like a wandering light in the sky? No, so the Earth is not a planet. Neither is Neptune. What they are are spherical objects orbiting the center of mass of local solar system, as well as the center of the galaxy, and the center of mass of the Local Group, etc. Call them "spherobs" or somesuch if you *must* have a simple word.
That's it! From another classical source: "Earth is a class M spherob".
Good judgement comes from experience, and experience comes from bad judgement.
- W. Wriston, former Citibank CEO
Just make the definition:
Anything larger than (some arbitrary size larger than Pluto but smaller than Mercury). All objects identified as planets prior to 1950 shall still be considered to be planets, even if they do not otherwise fit this definition.
That's the easy way of saying that Pluto shouldn't be a planet, but will be considered one anyway. I don't understand all the fuss. It's not like Pluto will have its feelings hurt or have a party one way or the other. Since I see more support for leaving it a planet, but poor Ceres ignored, we should just make an exception for Pluto (of course, not by name, since that would show planetary favoritism).
Learn to love Alaska
This is a ridiculous argument. We define the word by what we know now, when we learn something new or find a body that doesnt fit the current definition of planet we change the definition. This is what a living language is. This is just ramblings by an ultra anal retentive who doesnt seem to realize that there are very few (if any) words that are defined the same way today as they were in the past. Personally I hope we never come up with a definitive definition of planet, that would mean everyone is done thinking about it.
Most people seem to trip up on the last part. I think the idea is that an object shouldn't have any "rivals" in its orbit, for lack of a better word. I was browsing some astronomy sites a few months ago and found a good page on Sedna which had a discussion of what should be considered a planet. This is before the recent reclassifications but I think it illustrates what the IAU was thinking. It's also interesting that Ceres was at first considered a planet but then was downgraded because it was found to just be one object in a belt of objects. This is exactly the same as what happened to Pluto.
I know there's going to be lots of weird shit in the galaxy which blurs the lines, but I think the current definition is pretty good for within our solar system. And after all, why should everything be easily classified? Isn't it the strange, hard-to-classify findings that usually advance science the most? We can make up new terms or modify the existing definitions as we find new objects.
Anyway, here's the words of someone who has forgotten more about astronomy than I've ever learned.
The word planet came to us from a Greek element meaning "passively drifting, wandering, or roaming"
lotsa planets out there
back in the day we didnt have no old school
The term "planet" will never be officially defined because no one besides some obsessive-compulsive grammar nazis cares whether some dead rock floating through outer space should be called "planet" or "planetoid".
Not a flamebait nor a troll, but the simple truth. Real scientists have better things to do than play around with semantics, and no one cares what the armchair astronomists say.
Forget magic. Any technology distinguishable from divine power is insufficiently advanced.
If you want the moon to be a planet, and greased the right palms, you could probably swing it.
Engineering is the art of compromise.
As our understanding growse =PlayList&p=7AD02778306883CB&index=0
You've got to change some definitions
http://www.youtube.com/watch?v=g2bN5KsCWZ8&featur
Never say never.
I love the smell of schadenfreude in the morning. :)
A better way to do it would be to set a minimum atmosphere, size, density for Planet/Dwarf Planet/Asteroid/Gas Giant classification...A nomenclature similar to Chemistry is needed.
Quite right. They're all planets but of different classes. We could list up all the types of planets we know about and assign alphabetic class numbers to them. An Earth-type planet could be, "Class M". I know, wild, original idea...
My God, it's Full of Source!
OUTSIDE_IP=$(dig +short my.ip @outsideip.net)
A continent is anything that would otherwise be considered an island, but is at least as large as Australia.
We should be able to come up with something similar for a planet. It might cause problems for Pluto, but we could certainly define it as anything orbiting a star that is not itself a star or black hole and is a coherent body at least as large as <insert arbitrary size>.
Don't thank God, thank a doctor!
I think that with all the feuding to define Pluto as a planet, we should first set a point of reference. Pluto should be that reference.
The criteria should be:
* Is it its own celestial body orbiting a sun that is equal to or larger than Pluto? If so, then yes.
* Does it have its own orbiting celestial moon? If so, then yes.
* Is it Rosie O'Donnell? No.
Then it's a planet.
- Just my $0.02, take with a grain of salt, your mileage may vary.
To an scientist everything is an object with properties.
A major reason behind the "uproar" about Pluto's "demotion" is the lack of separation between common and scientific classification of solar system objects. It only makes sense that as scientists and astronomers learn more about the objects in space their classifications will change and evolve accordingly. Unfortunately the scientific ontology blends with our common-use terms, thus creating emotional debate over a question of taxonomy.
w eexplore/Why_We_23_prt.htm
Here's a great article by NASA's Chief Historian (who actually voted for the new planet definition: http://www.nasa.gov/mission_pages/exploration/why
To help us navigate the goofily drawn line between planet and dog, perhaps it would be "civil" of us to just create the abstract notion of a "union of particles orbiting the sun". We could then define Pluto as one of those, and leave the religious issue of which such unions should be marryable to the word "planet" to the respective scientific faiths to sort out. I'm sure that with an appropriate number of masses it will all work out divinely.
Kent M Pitman
Philosopher, Technologist, Writer
Yes maybe this has come up but here it is:
...
Firstly all established planets (e.g.Pluto) in the Solar System can keep their normal planet status. We can keep the text books as they are because it's straight forward for the public and almost the truth!
Secondly all exo-solar planets or undiscovered Solar System planets should be classified within a category:
1. Dwarfs (think Sedna)
2. Terrestrial (Earth type planets, e.g. Venus, Mars)
3. Giants
This divides them up into rough sizes (you can define them as you wish according to physics)
Thirdly the categories are divided into smaller sub categories describing their general properties such as:
Hot/Cold, Lone (in the case of starless planets), Icey/Rocky/Gas, Remnant
This should be enough to allow for the right information to be used in the right context.
For example, Jupiter could be described as a planet, but an exo planet with the same properties should not be called "just a planet", but a "Cold Gas Giant". Pluto type objects would be classified as "Icey Dwarfs". The exo planets around a Pulsar (first exo planets detected), could be called "Terrestrial Remnants". The properties could be stacked according to whatever context they are used in. A basic course may only call Jupiter class plants Hot or Cold Gas Giants. But astronomers would be able to say something like "Very Short Period Gas Giant", for a Jupiter class planet that is very close to its parent star.
Then again should we leave the definition of planets up to astronomers? They didn't do too well with metals!
The classification of living organisms is in constant flux. A century or so ago, there were two kingdoms: animalia and plantae. Parameciums were animals, mushrooms were plants.
When I was in high school, there were three: animal, vegetable, and protista, it being felt that single-celled organisms really weren't typical animals. It may shock some--it certainly shocked cellular biologists when I was in grad school--to know that circa 1940-1950 there was serious consideration given to the concept that protozoans were not single-celled organisms, but were "acellular." Just as with is-Pluto-a-planet you can give a good argument that they should be regarded as having a single cell (they have a nucleus, etc.) but you can also give a good argument that they are extremely different from the cells of higher organisms (they have "organelles").
Today, depending on what book you read, there seem to typically be about five kingdoms: Monera (bacteria and green algae, the procaryotes), Protista (single-celled eucaryotes), Fungi, Plantae, and Animalia. I'll bet that splitting out Fungi from Plantae was controversial. Lately, they seem to be splitting the Monera into Eubacteria and Archaebacteria.
Now, this sort of activity is not meaningless, but it is hardly objective, either. How many kingdoms there are and what the textbooks print tends to depend on the social hierarchy in the scientific community, whose opinion carries the most weight with the textbook authors, and so forth.
Of course the word "planet" is never going to be finally defined. It's in the eye of the beholder, and as planetary science evolves, what characteristics are consider to be useful for classifying objects in space are going to change over time. If someone were to discover tomorrow that six of the planets have some obviously important, striking characteristic in common with each other that the other large orbiting objects lack, there would probably be a faction that would argue that that is the defining characteristic of a planet.
And so it goes.
What I don't understand is why people think this is a particularly important or interesting topic. It's as if some convention of geographers decided that Europe should not be considered a continent and millions of schoolchildren got bent out of shape about it.
Some textbooks say there are seven colors of the spectrum, red, orange, yellow, green, blue, indigo, and violet. Some say there are only six, omitting indigo. Why is frickin' indigo in there anyway, since hardly anyone knows what color it is, and it doesn't look particularly like a separate color? Why don't we say the colors of the spectrum are red, orange, yellow, smaragdine, green, blue, indigo, and violet?
Because Sir Isaac Newton a) happened to have a prism that dispersed the spectrum widely at the short wavelengths, making "room" for more colors at the blue-violet end, and b) had a cockamamie theory that since there are seven notes in the diatonic scale there oughta be seven colors in the spectrum. So he described the ROY G. BIV colors, and Newton being a man of rather considerable authority in the field, textbook writers blindly copied him and each other for centuries.
We're never going to have a final definition of "the colors of the spectrum," either.
"How to Do Nothing," kids activities, back in print!
Pluto hasn't changed one atom based on which category we put it in. How things are classified is a human activity, and matters only to us. Which also means that we can do whatever we damn well please here. We're just calling it something. We can decide what to call it. All definitions are an agreement to use a word for a given meaning, whether the word is Pluto or pancake.
Biologists have been having this type of problem a lot longer than astronomers: the problem where you can't figure out which species something belongs in, for instance. And we biologists have the solution. (But will the astronomers listen? No-o-o. Of course not. ;-}) When new information comes in suggesting that something belongs in a new category, that something is renamed, EXCEPT when doing so would disrupt a name in wide usage. Then it can be conserved. In that case, only the scientists have to worry about where it "really" belongs, and everybody else can go about their business without a vocabulary list.
Conservation of names is an especially good idea in cases like Pluto, where the scientists themselves haven't entirely agreed yet. They could simply agree to conserve Pluto's definition as a planet, and then continue arguing about the exact definition, which, as the article says, never actually has to end in agreement. And that's because we're talking about a category here, a human construct, whose boundaries exist only in our heads. (I posted a bit more on this under What Pluto really is)
Here's what the definition should be;
Planet: Any planetary body that has an atmosphere that orbits that may or may not a star. If they exist, this could include rogue planets.
Moon: Any planetary body that orbits a planet is considered a moon with one exception of similar asteroids as Phobos or Deimos.
Asteroids, Comets, Etc: Any planetary body floating anywhere that do not have an atmosphere and primary made minerals of nearby other asteroids. Phobos and Deimos
\
I can define planet easily, Planet: n, Wandering star.
I'll take your "dwarf planet" and raise you a "hob-goblin planet".
Task Mangler
As I figure the difference between "large rock orbiting the sun" and "larger rock orbiting the sun" will never be too important, why not define a planet by some standard of surface gravity, the point where it can hold gases without requiring the gases to be attracted to the body by some other force?
A nomenclature similar to Chemistry is needed.
Needed for what? As TFA quotes Geoff Marcy at the very end: "Categorizing them does not magically add insight."
Are you adequate?
As the final sentence in the TFA (attributed to one Geoff Marcy) puts it: "Categorizing them does not magically add insight." Just because you have a set of rules, no matter how precise, that enables you to take arbitrarily many celestial objects and bin each of them into one category from a fixed set, doesn't mean that you've accomplished anything of interest.
Categorization schemes only make sense in the light of a theory that provides some insight about its object (e.g., allows us to use observations in one domain to make accurate predictions in another), and even better, allows us to do stuff we couldn't before. The correct order to follow here is theory first, categorization second.
In your case, you clearly have one theory in mind: a simple two-body system where one of the bodies orbits the other, which is somehow designated as "the sun" (by some procedure you don't bother to specify). That's just one special subcase of mechanics, and in fact, a theoretical one that never in fact holds. Why should it be privileged at all?
While I'm at it: the fact that categorization schemes are relative to theories also implies that there isn't one thing as The One True Categorization of a subject domain. The article provides a great example, in that some astronomers study the dynamics of celestial objects, while other study their composition. If your theory tells you that these two aspects of what intuitively to us are the same objects are orthogonal (as Newtonian mechanics usually assumes, by treating celestial objects as indivisible bodies in the theoretical sense), then whatever classification either branch comes up with will be orthogonal to the other's.
Are you adequate?
A planet is a body with a solid or liquid mass that's large enough to become nearly spherical under it's own gravitational pull and that's composed (the solid or liquid core) by at least 50% materials that are solid at a temperature of 300 kelvin and that's not orbiting another planet more than doubling its mass and that's not generating significant heat from fusion reaction of its mass. If it needs to be orbiting to a star or not, that's left to others to decide. But this will do away with asteroids, stars, coments and moons, while still allowing for solid planets (big and small) and gaseous planets (since they have a solid or liquid metallic core). And it is logical, because it discards the unwanted bodies for its "undesirable" qualities (comets for not being stable having their mass composed of ice, asteroids for not having significant gravity, moons for orbiting other planets and stars for being lit) and not for some arbitrary parameter. The details of how round they have to be, the exact cutoff temperature, the mass percentage between twins and what is "significant" heat can be discussed, but all those parameters can be swayed a lot without including any unwanted bodies or excluding any known planet.
Scientists can invent some crazy new words to define various types of planet, and just leave "planet" being an imprecise term used by the general public.
The IAU had a great draft which basically said if it orbited a star, and was roughly spherical under its own gravity, and wasn't itself undergoing nuclear fusion it was a planet. Nothing at all wrong with this definition. I couldn't give a shit if Pluto was called a planet or an Oreo. THAT definition was self consistent and just plain made sense.
However a definition that makes a "Dwarf Planet" not a planet, and anything not orbiting our sun not a planet (despite the scientific community having talked and of extrasolar planets for decades now) is just inane BS. It's just confusing, unintuitive bad classification and therefore bad science.
These posts express my own personal views, not those of my employer
DEFINITION OF PLANET:
Star - starlet
Plane - planet
so...
A planet is a term for a small plane.
Planet: Any solid that, when destroyed, is insignificant next to the power of the force.