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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."
it seems silly to go about redefining something like what constitutes a planet. what possible scientific value could this have? why can't we be content to keep the traditional designations of what make up a planet?
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
does a planet have to orbit a star? Can it orbit other things?
:-)
Well, if you're nit-picking about the original poster's definition, you should read the definition you're nit-picking about.
How about this: A mass with an self-sustained atmosphere of measurable magnitude.
I swear, the reason we're not in flying cars powered by cold fusion is because the world's best and brightest are too busy arguing over stupid things like the definition of a planet. Maybe I need to rethink my concepts of "best" and "brightest."
How do we solve that? We say what we mean in a particular context and then use the word as a shorthand. "In this paper, we will use the term 'planet' to refer to extrasolar bodies with diameters over 700km and masses less than 13 times the mass of Jupiter." "In this paper, we will be talking about the traditional nine planets of the solar system, Mercury, Venus, ..." Etc.
Terms like "planet" would actually be less useful if they did have a precise definition, because than each of those papers would have to use a much more awkward circumlocution when referring to bodies that don't meet the definition precisely.
But it's proximity to other objects. That's why Pluto should remain a planet. There isn't really anything else around it, so it should be a planet. Ceres on the other hand, is in the middle of a large belt of other similarly sized objects, so it should stay as what it is, an asteroid.
I think you mean: Should have 5% of the size of the parent star, not 5% bigger...
It doesn't work any way you slice it. He grossly underestimated how big stars are.
Even at 5%, it wouldn't look good for Earth's status as a planet. We aren't even 1% the Sun's size, and we don't have even a tenth of one percent of the Sun's mass... and our Sun is rather small as far as stars go.
> Pluto ~ 1130
Pluto is not a planet to the definition. However, it is the first thing "close" to a planet, which Americans discovered. They wanted to join the "hall of fame" of planet discoverers, so they convinced the world that they better accept Pluto as planet.
Here's a link (of many) with more details: http://www.theatlantic.com/issues/98feb/pluto.htm
Marc
PS: History repeats, you can see it in daily news. What doesn't fit, is made fit.
scripsit minus_273:
If they weren't doing photosynthesis, however, why on earth (er, on planet?) would they look anything like terrestrial plants? There is a practically infinite variety of forms to choose from, and non-photosynthetic plants could just as well look like mushrooms, or brown algae, or whatever -- but there'd be no reason to grow up if they weren't trying to reach light.
In principio creauit Linus Linucem.
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.
The moon fits point 'a', point 'b' and point c, but does not fit point 'd' or point 'e'; therefore is not a planet. The moon orbits the Earth (a planet.) The Earth-Moon unit (no relation to the Zappa's) orbit the sun (which is a star.) The moon itself doesn't orbit the sun, rather it orbits the sun along with us. Ergo, it's a satellite (and not the Toshiba kind, either.)