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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."
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
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 just like taxonomy... some scientists like to lump similar creatures into one family or genus, while others like to split them up into different categories based on minor differences.
Looks like astronomers do it too.
Different discipline, same problem.
Even if a man chops off your hand with a sword, you still have two nice, sharp bones to stick in his eyes.
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
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.
I think you missed the most important comparison to support your claim:
Mercury: 4880 km
Ganymede and Titan are both larger than Mercury. This is important because there's no argument about Mercury's standing as a "real" planet.
But then again, I could be wrong.