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Defining "Planet"
beardoc writes "The Sydney Morning Herald is running a story today about a controversial proposal to define what size a planet might be - depending on what the final definition of how big a planet is, we could end up losing Pluto (at 2300 kilometres) to the status of "asteroid" or gaining three more planets - Quaoar, Varuna and Ceres."
... agreed to be "Marlon Brando"
If someone bothered to name a Roman god after it, it's a planet. Pluto, Mars, Jupiter--all friendly planets.
Alpha Centauri? Bah--probably a reflection off that Hubble thingy.
We recently had heard in the office over one of the Yellow Machine that's made by Anthology Solutions.
Wouldn't it make sense to take into account whether the planet could feasibly sustain life too? I mean could a 700km round body in space support an atmosphere?
(stolen from DaBum) I am dyslexia of borg - your ass will be laminated.
Planet: n. Any object orbiting a star, not orbiting a planet, and having a radius greater than the radius of Pluto minus one millimeter.
I went to an astronomy talk at the University of Toronto a few years ago. The presenter defined a planet as any celestial body that doesn't radiate light. That explicitly includes asteroids and moons. Why is it necessary to make the distinction between planet and asteroid?
The whole point of the article is to arbitrarily define the distinction which just proves how stupid it is.
Jason
ProfQuotes
they say bodies larger than 700km go from being potatoe shaped to round. why not set a defined width above this 'minimum', and anything larger be called a planet? twice the minimum sounds plausible, and that means Pluto would still be defined as planet.
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Because the traditional designation of what made up a planet was anything that we could find that orbits the sun. We didn't include comets because they looked different from planets and we didn't include asteroids because we couldn't resolve them. Now that we continue to find many large objects that are really little different from Pluto it has suddenly become important to have a real definition of which are planets and which are just big asteroids.
Also, as we find bodies orbiting other stars, the traditional designations for planets is obviously useless.
We hope your rules and wisdom choke you / Now we are one in everlasting peace
Why do they always need to complicate things. I thought size doesnt matter.
I've left to find myself. If you happen to see me, please, keep me there until I return.
a) this is science, not tradition, scientific terms need an absolute definition.
b) traditionally, you only had the naked-eye planets: Mercury, venus, Mars, Jupiter, Saturn. What do you call the other gas giants? Not to mention, Mercury was thought to be two planets by some (the morning and evening star).
c) my opinion, just set it so that Pluto-size is the cut-off. Anything smaller isn't one. However, in a few centuries when we can detect "planets" in other solar systems this would seem a bit heliocentric, so I can see the Basri's point (in the FA: "Basri's definition, a planet must orbit a star, not another planet, and it must be round. That means it must be 700 kilometres in diameter, when gravity moulds it into a sphere, or bigger.").
People keep trying to wage a debate about this, but no matter what technical hand-waving is going on in the press, the International Astronomical Union is committed to the traditional status of all nine planets, and isn't likely to change that opinion.
--brian
As a representative one of the nine planets, I find this proposal deeply troubling, especially since there are not any other representatives from the other eight. Once a planet is classified as an "asteroid" or "floating piece of shit with gravity", it not only loses its prestige, but also, it cannot apply for federal grants, and hence, usually suffers a major economic blow. Laugh you may, but I've seen planets go from a heavenly body to a drunk spinning horizontal and finally distingrate into an asteroid belt in no time. We must support our planets because if we don't, then who will?
With the discovery over the past few decades of the Oort Cloud and Kupier Belt, it seems obvious that there are tens, if not hundreds/thousands of Pluto-sized objects out there. Obviously, we're not going to name all 10,000 of these rocks "planets." But then again, Pluto has a special place in history as the last "great" planet discovery on the level of Uranus and Neptune, so purists wouldn't want to ruin that by demoting it.
:-) Therefore, I say we define a planet however they want, but keep Pluto for historical significance. I knew med school would start paying off soon :-)
My solution? Define "Planet" as something bigger than Pluto, maybe with Mercury as the smallest, or whatever. But keep Pluto as a planet (as an exception ot the rule) for historical purposes. But, you may be thinking, "that's so stupid! Why give something a name if that name is now invalid?" The answer? We do it all the time. Here's an example...
Take a look at ANY diet softdrink/diet product with Nutrasweet. It warns you that this product contains "Phenylalanine" and should not be taken by "Pheylketonurics." Take a look at that word. It's called "Phenyl-keton-uria" (PKU) because years ago, people with this disease were diagnosed when "Phenylketones" were detected in their Urine. However, no one diagnoses PKU via a urine test anymore, they use another method. So should we change the name of the disease? Of course not. But due to historical significance, we keep it. Unlike the Indian/Native American designation, "Planet Pluto" should not offend anyone
This is sort of handled(here):
Since the COM is inside the Earth, I think it's fair to say that the Moon orbits the Earth (and not vice versa).
The Mongrel Dogs Who Teach
This superficial naming convention makes absolutely no difference at all. It has no effect on anything.
It would be like if you changed the biological classification system so that bears were no longer Mammals. What difference does this make to the bears? None. What difference does this make in how we relate to bears? None.
It is simply an arbitrary naming convention. As are all naming conventions.
It reminds me of an old Zen saying that I am likely paraphrasing miserably:
"Before Zen, a mountain is a mountain. While one is practicing Zen, a mountain is no longer a mountain. After Zen, a mountain is once again a mountain."
Justin Dubs
Alone in it's orbit, it's moons orbits it
isn't too far out
Sorry about the writing. Robot fingers, you know? Cliff Steele in DOOM PATROL #23
Why is there so much mention of radius and size and such. It's just so petty. I would think in this enlightened age we'd all know:
It's not the size that matters, it's how you orbit!
*Dodging tomatoes should be a sport*
Does jupiter have volcanic activity?
Just use the Star Trek planet classifications... Come on, it's time to make use of sci fi in astronomy for once. :-) Hmm, btw, I wonder what the heck the copyright at the top of the page is about? Courtesy JPL? Errr...
Beware: In C++, your friends can see your privates!
Any Definition for "planet" will be arbitrary. Is a little ball of snow and ice on a highly elongated orbit a planet? No. It's a comet. Is a gas giant that generates more heat internally than it receives from the star it orbits a planet? Maybe, maybe not. OK, perhaps that's not arbitrary. If the thing gives more heat then it gets, then perhaps you could classify it as a brown dwarf, but what if the star it orbits flares up? Then does it suddenly become a planet because it starts receiving more heat?
I think the only thing we can conclude is that the definitions for "planet", "moon", "ring material", "asteroid", "comet" and "brown dwarf" are all arbitrary. It's all a matter of perspective.
So, here are my definitions:
Planet -- orbits a star, is big enough so that gravitational pull forces it to appear round or smoothly eliptical to the naked eye.
Asteroid -- orbits a star, If it's not round due to gravity, it's definitely an asteroid. Problem--this makes Ceres a planet.
Moon -- orbits a planet, unless it's not round then it's just a "captured asteroid". Problem--this makes Deimos and Phobos non-moons.
Ring material -- If the human eye perceives the planet as having rings, then any ojbect within the region containing the perceived rings is "ring material" regardless of how big it is or how it's shaped.
Comet -- any item that forms a tail when passing close to the star.
Brown dwarf -- Gives off more heat then it gets.
Really, when you get right down to it, all of these things are just "stuff that's not space". Choosing to call them "planet" or "comet" makes as much sense as choosing to call one city Cincinnati and another Buffalo. Somebody's gotta name the thing. Now, people have been living in Buffalo a long time, and they've been calling Pluto a planet a long time too. Whaddya say we make a deal? Get Buffalo to change its name to Cincinnati, and we can stop calling Pluto a planet. Now, what do I call a single hydrogen atom on a hyperbolic trajectory with Jupiter?
For all intensive purposes, "whom" is no longer a word. That begs the question, "who cares"?
Badly?
This is because the moon is so massive and close to earth compared to all other planetary moons in the solar system.
We need to define what a "moon" is, and I would suggest a definition based around the relative gravitational forces on the body of sun and primary. The sun is about 300000 earth masses and is about 400 times as far from the moon as the earth is - so a rough calculation suggests that the sun-moon gravity is about twice that between the moon and the earth. On this basis, the moon seems to be a satellite of the sun rather than the earth, and the earth-moon system is a dual planet. Despite the size of the inner moons of Jupiter, their paths are almost totally controlled by Jupiter's gravity and they are moons.
I can't find the reference, but I think Isaac Asimov may have made this point at greater length in a magazine article.
Panurge has posted for the last time. Thanks for the positive moderations.
scientific terms need an absolute definition
A rigorous definition may be necessary but not sufficient for the "usefulness" of a scientific term. In this case, it doesn't seem like the proposed definitions are useful.
If we determined (for example) that bodies above a certain mass had some other properties of interest, or that stellar systems with a certain number of bodies above a certain mass had some interesting properties, then it would be useful to define "planets" as being bodies of at least that mass. The class of such bodies would be a regular subject of analysis, and it's easier to say "planets" than to say "non-stellar gravitationally stellar-bound bodies of Werkeltroff-Schmeltergruber-Minayevich mass or greater."
See, in the ordinary course of developing a scientific lexicon, we discover scientifically useful concepts, and then define terms for those concepts in order to provide economy of expression.
In this case, however, it seems that we have a term that already exists in the popular lexicon, but no related scientific concept with a compelling need for the term.
So why bother? Why not just allow the term to continue its peaceful existence in the popular lexicon, without attaching an arbitrary definition to it? Are we trying to serve some purpose other than allowing slashdot geeks another way to point out where the popular press gets something wrong? If we can identify a purpose for a definition, I the definition will probably follow naturually from the identified purpose; if not, then the whole discussion is silly, at best.
Now if we could just lose the rest of Disney, our freedom might be safe.
-Miko
Miko O'Sullivan