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Is {pluto|sedna} A Planet?
Dr. Zowie writes "NASA's announcement last week of Sedna's discovery reignited the debate
over whether Pluto is a planet. Dr. Alan Stern a noted planetary scientist and leader of the New Horizons mission to Pluto, pours on some gasoline with this
article in which he skewers the various arguments against Pluto-as-planet. Choice quotes include 'You wouldn't deny a chihauhau a place among dogs because it is too small,' and 'if your brain was so completely full of names of people that it just couldn't take any more, would anyone new who you met after that, therefore not be a person?'"
he adresses this in the article for the gravity rules there are two criteria 1. orbits the sun (or star for another system) 2. is above some critical mass (large enough to become rounded by its own mass, which is only a few hundred kilometers in diameter) and yes this includes some asteroids
Well Pluto's moon is called Charon. The ferryman of the dead. Is that good enough for you.
But how irregularly shaped does it have to be to qualify for non-planethood? Even the gas giants aren't perfect spheres.
Have you been touched by his noodly appendage?
Harvard has a nice page with lots of links an references for people looking to dig deeper into the Minor Planet definition under which asteroids like Ceres and Sedna fall under.
Saskboy's blog is good. 9 out of 10 dentists agree.
Well the concept of a species might not be the best example. Two individuals are generally recognized to be of the same species if they can mate and produce fertile offspring. So, for the most part it's not simply arbitrary set determination.
See: Mule
Tomato is, and always has been, a fruit.
The supreme court rulled that it was a vegitibale so schools could meet nutrienal guide lines.
Rule of thumb:
Does it have seeds? then its a fruit.
The Kruger Dunning explains most post on
The original seven, actually. The sun and the moon were planets. And yes, they all revolved around Earth. Church "scientists" were the first to add to this system; they put Heaven above the planets.
Gates' Law: Every 18 months, the speed of software halves.
I cite Cecil Adams of The Straight Dope, font of all knowledge, to say with authority:
The tomato is botanically a fruit.
Brontosaurus never existed.
And you can blame the Greeks for the continent thing.
That Cecil! Is there anything he doesn't know?
-Carolyn
Like Daddy always said: if you can't dazzle 'em with brilliance, baffle 'em with bullshit.
Yes, that would be why he stated that GRAVITY would be making the object round, not some other force. So, no, by that definition water bubbles would not be planets.
common sense: noun
What those who are ignorant of the subject matter think; usually wrong.
Potato is a nightshade IIRC. As is the tobbacco plant.
As for the tomato == vegetable idea, if you don't know this, it may interest you. The supreme court of the united states declared the tomato a vegetable sometime in teh 1830s. At that time vegetables were taxed and fruits were not. A fruit importer was shipping tomatoes tax free, and he got in trouble for it. After that decision, tomatoes had all the legal attributes that vegetables did.
The guy's name was John Nix if you want to google up some more information.
Etiquette is etiquette. He kills his mother but he can't wear grey trousers.
You're all wrong. A tomato is BOTH a fruit AND a vegetable. Who ever said they are mutually exclusive?
Main Entry: vegetable
1 : PLANT 1b
2 : a usually herbaceous plant (as the cabbage, bean, or potato) grown for an edible part that is usually eaten as part of a meal; also : such edible part
Main Entry: fruit
Function: noun
1 a : a product of plant growth (as grain, vegetables, or cotton) b (1) : the usually edible reproductive body of a seed plant; especially : one having a sweet pulp associated with the seed (2) : a succulent plant part (as the petioles of a rhubarb plant) used chiefly in a dessert or sweet course c : a dish, quantity, or diet of fruits d : a product of fertilization in a plant with its modified envelopes or appendages; specifically : the ripened ovary of a seed plant and its contents
Potatoes are vegetables. Specifically, they are tubers, parts of the root system that enlarge and store energy. They are also in the same family as peppers, eggplants, and tomatoes, all of which actually are fruits.
However, peppers, eggplants, and tomatoes are also all vegetables. The two are not exclusive, as fruit is a technical term with a specific definition. A vegetable is any plant grown to be eaten, or the part of the plant that is eaten. Fruits are vegetables. So are nuts and grains.
Everyone knows that a tomato is a fruit. Most wrongly assume that means it isn't also a vegetable. The lesson here is, check your facts before you go spouting off in a supercilious manner.
- None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton
"One doesn't deny a Chihuahua a place among dogs because it is too small."
First: The designation 'planet' should mean something. Sure we can group small dogs under the category of dogs but that doesn't mean we can go around calling pomeranians' greyhounds. The same with planets. We can group pluto and sedna under the category of masses but we shouldn't call them planets. Planets should be its own category of the junk floating around in the universe, just as asteroids and comets are categories. When someone says this object is a planet we should thus be able to make some assumptions about that object. Otherwise we have to break that category up even more. If we have to have sedna added and a couple hundred other, the category of planets becomes so vague that it becomes meaningless. Thus we will have to break the category of planets up into sub categories in order to get any meaning out of it: gas gaints, rocky planets, etc.. Think of it like the dogs again. If we call every dog a pomeranian then the label 'pomeranian' loses its meaning.
Now the problems with his gravity rules. The first problem is moons. No one wants to call luna a planet. If we go around saying a planet in the solar system (Jupiter) has 32 other planets orbiting it, things will get very confusing awfully quick. So we would want to declare that for it to be a planet it has to orbit the sun. But then their is the problem of 'planets' that orbit each other. For example, we see this in some asteroids - two asteroids that orbit each other while traveling in a circular path around the sun - similiar to binary star systems where two stars orbit each other and tavel in a circular path around the galaxy. They can't both be moons. They can't both be planets. And what about rogue planets that no longer orbit a star but have been orphaned and are currently floating in interstellar space.
The second problem is comet-like bodies. What if you have a planet that as it orbits its sun sheds its atmosphere and mass to the point that it loses the gravity necessary to keep it circular. Likewise, what if you run into an asteroid that through a series of collisions gains enough mass to become a planet. This is fine but what happens when you have a whole belt of such objects. When you classify something, its best it stays in that classification for awhile or else the act of classification becomes somewhat meaningless. For example, you don't classify water by its mass in a rain storm cause that mass is constantly changing. Rather you state the rate of that change. If you didn't, you'd be forced to constantly reclassify it every observation.
So simply stating that gravity rule as the only criteria doesn't work. We'd have to make it more complex. Moons aren't planets (assuming you still want the word moon and planet to mean anything - and yes I know some moons could have their own moons). Belts like the asteroid belt and the kuiper belt where objects could conceivably change in every observation from planet to non planet and back would create a nightmare for astronomers using such a system. And remember these are only problems we face with a small data set like our solar system. Add in problems like the Super jupiters, some of which are undoubtfully brown stars or close to becoming them, and other as of yet unknowns and one could only imagine even more problems would arise in the gravity rule system. Now if these means adding addition requirements or not, or perhaps just abandoning the whole system is anybodies guess. He's write in stating you can't just use the old size requirement - but that was and is why we called pluto a planet and ceres an asteroid. Becuase someone said theres a size difference - there is really no other reason. Some asteroids have atmospheres. Some have moons. Some planets don't have moons. Some planets have moons larger than other planets. Perhaps the best bet is to just throw all the labels out and start over.
There's a growing sense that even if The Future comes,
most of us won't be able to afford it.
-- Lemmy
Ida and Dactl
From the article:
The main problem is that as we discover new objects, some planets may cease to become planets. And what happens if a planet shifts its orbit closer to a bigger planet? Does it stop being a planet until it moves far enough away?
Having read the article, I like his criterion: massive anough for gravity to form it into a spherical object. This doesn't change over time; it's based on physics; and it's very similar to the criterion for whether or not an object is a star (massive enough for fusion to provide the majority of its energy).
Freedom to fear. Freedom from thought. Freedom to kill.
I guess the War on Terror really is about freedom!
But we are talking about what you mean when you say a word. The only evidence that matters is usage. If you say "fruits" when actually what you are talking about is tomatoes and cucumers and squash and pumpkins, people are going to be misled.
In real world usage, having high levels of sugar is a requirement for fruit, being from an herbacious plant is a requirement for vegetables. Tomatoes don't have as much sugar as most things considered fruit, and they certainly are from herbacious plants.
Yes and then the Victorians invented the time machine and went back and told Aristotle about it, causing him to write Categories.
Don't blame me; I'm never given mod points.
http://caselaw.lp.findlaw.com/scripts/getcase.pl?n avby=search&court=US&case=/us/149/304.html
Actually, the center of mass of the earth-moon system is about 1000 km down from the Earth's surface. But it's much closer to the surface than to the center.
Despite this, many astronomers still classify the earth-moon system as a double planet rather than as a primary+satellite. This is partly because, as Alan Stern argues, they basically do use the self-gravity rule to define "planet". Another line of reasoning is that the moon's orbit is everywhere concave to the sun, so technically it isn't orbiting the earth. Rather, both are in the same orbit about the sun, and are doing the "orbital dance" that two bodies in a common orbit do.
In any case, words like "planet" are human concepts. The universe doesn't have to supply objects that fit nicely into our classificational bins, and in this case, it doesn't.
Those who do study history are doomed to stand helplessly by while everyone else repeats it.
Anyway. The more phenomena we discover, and the faster we discover them, the less interesting each individual one becomes. The more diverse they are, the less likely it is that the 'labels' invented 3000 years ago will still make sense. We're lucky that the simple categorization 'planet/comet/asteroid' has held up as long as it has. We've patched it up with TNOs and KPOs and so on, but at some point it'll be a continuum. A sparsely sampled continuum, but a continuum nonetheless.
The IAU's current concern is to distinguish between extrasolar planets and dark stars. It takes about 13x the mass of Jupiter before an object generates the gravitational pressure needed to ignite the D-D reaction. So the IAU says that if it's smaller than 13x Jupiter, it's a planet. Bigger than that, it's a "brown dwarf" if not shining.