5 ms·

I don't like the classification of dwarf planet. The classification should be based on its size, shape, and make up. Instead they classified it based on the num

I don't like the classification of dwarf planet. The classification should be based on its size, shape, and make up. Instead they classified it based on the number of objects in its orbit, which is so arbitrary and weird. If hypothetically we cleared up the objects and dumped them in Earths orbit, Pluto would suddenly become a planet and Earth would lose its classification. Just bite the bullet and accept there are a lot of small planets in our solar system, or classify them based on size.

dalke 10y ago
The odd phrase "clearing the neighborhood around its orbit" exists because people want to think of Ganymede (which is bigger than Mercury) as a moon, not a planet, which your proposal would do. If hypothetically we moved the Earth so it orbits Jupiter, then it would be a moon, yes? See also https://en.wikipedia.org/wiki/Clearing_the_neighbourhood#Disagreement https://en.wikipedia.org/wiki/Clearing_the_neighbourhood#Dis... .
- Houshalter 10y ago
  Yes I accept orbiting the sun and not another object, as a reasonable criteria of a planet. That's included in the old definition. The new definition goes well beyond that though. If there are asteroids and debris in it's orbit around the sun, it no longer counts as a planet. It's really weird, and it's only purpose is to exclude the newly discovered planets from that classification.
  - dalke 10y ago
    Yes, it is weird, but I disagree with your interpretation. You wrote: "If there are asteroids and debris in it's orbit around the sun, it no longer counts as a planet." That Wikipedia link I pointed to says: "As to the extent of orbit clearing required, Jean-Luc Margot emphasises "a planet can never completely clear its orbital zone, because gravitational and radiative forces continually perturb the orbits of asteroids and comets into planet-crossing orbits" and states that the IAU did not intend the impossible standard of impeccable orbit clearing.[2] It further lists a few attempts to define things more rigorously. You write: "it's only purpose is to exclude the newly discovered planets from that classification". The same page also points out "In 2015, a proposal was made to use the criterion in extending the definition to exoplanets". This is from the same Margot, whose proposed criteria can "categorise a body based only on its own mass, its semi-major axis, and its star's mass."
parenthephobia 10y ago
> The classification should be based on its size, shape, and make up. Instead they classified it based on the number of objects in its orbit, which is so arbitrary and weird. Why should it be one rather than the other? What harm or benefit comes from Pluto being called, or not being called, a planet? > If hypothetically we cleared up the objects and dumped them in Earths orbit, Pluto would suddenly become a planet and Earth would lose its classification. No, because the definition requires that a planet clears its own neighbourhood. Having a nearby technological civilization clean up its neighbourhood for it doesn't cut it. > Just bite the bullet and accept there are a lot of small planets in our solar system Dwarf planets, you might say.
- Houshalter 10y ago
  >Why should it be one rather than the other? What harm or benefit comes from Pluto being called, or not being called, a planet? It violates everyone's internal model of the word "planet". Everyone knows what a planet is, and the formal definition should try to match our internal models as closely as possible. To do otherwise feels wrong and arbitrary. >No, because the definition requires that a planet clears its own neighbourhood. Having a nearby technological civilization clean up its neighbourhood for it doesn't cut it. So now the definition is based on history? We can't determine what is a planet based on just observing it, we have to know how it came to exist in that state? If we ever travel to other solar systems, we will never be able to know whether they are true planets or not. For all we know aliens or other events cleared the orbits before we observed them. >Dwarf planets, you might say. Highly misleading. Dwarf implies it's just small, and if it was bigger it would be a regular planet. But the definition isn't based on size.
  - eropple 10y ago
    If it were bigger, weren't it clear its own neighborhood? Is there an example of a sufficiently large body that doesn't? (I'm by no means an expert, that's why I'm asking.)
  - macintux 10y ago
    > If we ever travel to other solar systems, we will never be able to know whether they are true planets or not. For all we know aliens or other events cleared the orbits before we observed them. I don't even. I mean, I'm not unfamiliar with lame arguments, having presented many in the past. But this one...wow.
thaumasiotes 10y ago
> If hypothetically we cleared up the objects and dumped them in Earths orbit, Pluto would suddenly become a planet and Earth would lose its classification. You seem to believe that if we cleared up those objects and dumped them into Earth's orbit, they would stay there.
- Houshalter 10y ago
  Eventually over many years they would clear up. But for a time Earth would no longer be a planet.
  - hawkice 10y ago
    Technically, planets are defined as celestial bodies with these characteristics, not astronomical bodies, and Earth, not being in the night sky, is not celestial. So if you want to play a technicality game then Earth might not be a planet right now.
    - dalke 10y ago
      That technical definition hasn't been in use for about 400 years, when the astronomers became Copernicans. Here's an astronomy book from 1842 talking about the Earth as the third planet from the Sun, and like all planets it revolves around the Sun: https://books.google.com/books?id=9AhbAAAAcAAJ&dq=planet%20earth&pg=PA78#v=onepage&q&f=false https://books.google.com/books?id=9AhbAAAAcAAJ&dq=planet%20e...
      - hawkice 10y ago
        You could not be more wrong about your correction. Not only is this definition current, it is in no way predicated on planets revolving around the Earth. The current IAU definition of a planet (the one that demoted Pluto) is: "A planet is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit." Very clearly says celestial body. The IAU does not seem to draw a distinction between celestial and astronomical bodies, and uses the terms interchangeably, but they are not synonyms. The distinction is usually irrelevant to those who need to make observations about astronomical bodies, so I can see why.

dalke 10y ago

The odd phrase "clearing the neighborhood around its orbit" exists because people want to think of Ganymede (which is bigger than Mercury) as a moon, not a planet, which your proposal would do. If hypothetically we moved the Earth so it orbits Jupiter, then it would be a moon, yes? See also https://en.wikipedia.org/wiki/Clearing_the_neighbourhood#Disagreement https://en.wikipedia.org/wiki/Clearing_the_neighbourhood#Dis... .

Houshalter 10y ago
Yes I accept orbiting the sun and not another object, as a reasonable criteria of a planet. That's included in the old definition. The new definition goes well beyond that though. If there are asteroids and debris in it's orbit around the sun, it no longer counts as a planet. It's really weird, and it's only purpose is to exclude the newly discovered planets from that classification.
- dalke 10y ago
  Yes, it is weird, but I disagree with your interpretation. You wrote: "If there are asteroids and debris in it's orbit around the sun, it no longer counts as a planet." That Wikipedia link I pointed to says: "As to the extent of orbit clearing required, Jean-Luc Margot emphasises "a planet can never completely clear its orbital zone, because gravitational and radiative forces continually perturb the orbits of asteroids and comets into planet-crossing orbits" and states that the IAU did not intend the impossible standard of impeccable orbit clearing.[2] It further lists a few attempts to define things more rigorously. You write: "it's only purpose is to exclude the newly discovered planets from that classification". The same page also points out "In 2015, a proposal was made to use the criterion in extending the definition to exoplanets". This is from the same Margot, whose proposed criteria can "categorise a body based only on its own mass, its semi-major axis, and its star's mass."

parenthephobia 10y ago

> The classification should be based on its size, shape, and make up. Instead they classified it based on the number of objects in its orbit, which is so arbitrary and weird. Why should it be one rather than the other? What harm or benefit comes from Pluto being called, or not being called, a planet? > If hypothetically we cleared up the objects and dumped them in Earths orbit, Pluto would suddenly become a planet and Earth would lose its classification. No, because the definition requires that a planet clears its own neighbourhood. Having a nearby technological civilization clean up its neighbourhood for it doesn't cut it. > Just bite the bullet and accept there are a lot of small planets in our solar system Dwarf planets, you might say.

Houshalter 10y ago
>Why should it be one rather than the other? What harm or benefit comes from Pluto being called, or not being called, a planet? It violates everyone's internal model of the word "planet". Everyone knows what a planet is, and the formal definition should try to match our internal models as closely as possible. To do otherwise feels wrong and arbitrary. >No, because the definition requires that a planet clears its own neighbourhood. Having a nearby technological civilization clean up its neighbourhood for it doesn't cut it. So now the definition is based on history? We can't determine what is a planet based on just observing it, we have to know how it came to exist in that state? If we ever travel to other solar systems, we will never be able to know whether they are true planets or not. For all we know aliens or other events cleared the orbits before we observed them. >Dwarf planets, you might say. Highly misleading. Dwarf implies it's just small, and if it was bigger it would be a regular planet. But the definition isn't based on size.
- eropple 10y ago
  If it were bigger, weren't it clear its own neighborhood? Is there an example of a sufficiently large body that doesn't? (I'm by no means an expert, that's why I'm asking.)
- macintux 10y ago
  > If we ever travel to other solar systems, we will never be able to know whether they are true planets or not. For all we know aliens or other events cleared the orbits before we observed them. I don't even. I mean, I'm not unfamiliar with lame arguments, having presented many in the past. But this one...wow.

thaumasiotes 10y ago

> If hypothetically we cleared up the objects and dumped them in Earths orbit, Pluto would suddenly become a planet and Earth would lose its classification. You seem to believe that if we cleared up those objects and dumped them into Earth's orbit, they would stay there.

Houshalter 10y ago
Eventually over many years they would clear up. But for a time Earth would no longer be a planet.
- hawkice 10y ago
  Technically, planets are defined as celestial bodies with these characteristics, not astronomical bodies, and Earth, not being in the night sky, is not celestial. So if you want to play a technicality game then Earth might not be a planet right now.
  - dalke 10y ago
    That technical definition hasn't been in use for about 400 years, when the astronomers became Copernicans. Here's an astronomy book from 1842 talking about the Earth as the third planet from the Sun, and like all planets it revolves around the Sun: https://books.google.com/books?id=9AhbAAAAcAAJ&dq=planet%20earth&pg=PA78#v=onepage&q&f=false https://books.google.com/books?id=9AhbAAAAcAAJ&dq=planet%20e...
    - hawkice 10y ago
      You could not be more wrong about your correction. Not only is this definition current, it is in no way predicated on planets revolving around the Earth. The current IAU definition of a planet (the one that demoted Pluto) is: "A planet is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit." Very clearly says celestial body. The IAU does not seem to draw a distinction between celestial and astronomical bodies, and uses the terms interchangeably, but they are not synonyms. The distinction is usually irrelevant to those who need to make observations about astronomical bodies, so I can see why.