Comment on Sad Ganymede noises

• Live_your_lives@lemmy.world ⁨1⁩ ⁨day⁩ ago

  What rules do you believe make for a definition that isn’t contrived? How do you exclude asteroids from your definition or reject other dwarf planets like Ceres without making up contrived exceptions of your own?

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  • mech@feddit.org ⁨1⁩ ⁨day⁩ ago

    Planets are round objects orbiting a star.

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    • Cethin@lemmy.zip ⁨13⁩ ⁨hours⁩ ago

      Many asteroids are round. The list of planets, under your definition, would be so large it isn’t useful anymore. Even when Ceres, Pluto, and Eris were called planets the list was getting too long, and there are several larger than Ceres. Including every nominally round object would be insane.

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    • yetAnotherUser@discuss.tchncs.de ⁨1⁩ ⁨day⁩ ago

      I propose a better definition:

      Planets are very large objects orbitting a star that dwarf everything nearby

      I’m pretty sure this is the intent of the IAU’s definition. It’s just more specific.

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      • Cethin@lemmy.zip ⁨13⁩ ⁨hours⁩ ago

        Ah, yes. “very large”, “dwarf everything”, and “nearby” are very specific terms…

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• sp3ctr4l@lemmy.dbzer0.com ⁨21⁩ ⁨hours⁩ ago

  No.

  Lets try a more simple metaphor.

  One person is navigating through a crowd, occasionally bumping into other people, having to juke and dodge their way around.

  Another person has an entourage or body guards to their front, and two gaggles of papparazzi following behind them, at each 45 degree angle to their rear, as they walk through an entire empty street 4 lane street, with some occsional people walking past the whole scene on the sidewalk.

  Pluto and Charon are basically an awkward, clumsy couple trying to get through a densely packed mall or convention.

  Neptune is Taylor Swift, as an entire parade float, just, herself, body guards, papparazzi. And I guess she also can have some literal ingroup orbiters who manage to stick around, their lives revolve around her the same way their walking patterns do.

  And then maybe, by chance, that awkward couple leaves the convention, gets lost, walks the wrong way to a restaurant, and end up just directly crossing the street that Swift walked down, 6 hours ago.

  There, is that a sufficiently relatable visual metaphor to illustrate the difference between the two situations?

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  • nexguy@lemmy.world ⁨21⁩ ⁨hours⁩ ago

    It’s a fine metaphor but it doesn’t work for scientific definitions which are exact. The IAU came up with the rule then had to make an exception to their own brand new rule in order to have Neptune remain a planet but not pluto even though both fail the rule. The exception is real and written down, not assumed.

    Yet again another of the IAU rules is the body has to be assume hydrostatic equilibrium (nearly round). Mercury is NOT in hydrostatic equilibrium and they knew this. So they just…decided… that Mercury is a planet anyway and does not have to follow that rule.

    So two planets don’t even follow the rules they made yet were unscientifically decided to be planets. Why? What was the point of it? Certainly wasn’t done for any scientific reason.

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    • sp3ctr4l@lemmy.dbzer0.com ⁨21⁩ ⁨hours⁩ ago

      Ok, so, Pluto is more spherical than Mercury, but the most important criteria is local gravitational dominance.

      Which Mercury has, but Pluto does not.

      I do not see how this is a difficult concept to grasp.

      Yeah, sometimes you can make a hasty definition, and then refine it to a level of consistent clarity, after it is justly critiqued, though it may be multi tiered and somewhat complex.

      Thats… thats how science works, thats like the entire fundamental concept of it, right there, improving the level of detail to which you understand reality, via empiricism, logic, participatory debate.

      The primary purpose of the planet defition refinenment is to emphasize the importance of relative local gravitational dominance.

      I’m trying to imagine you using this kind of logic with like, biological taxonomy.

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      • nexguy@lemmy.world ⁨20⁩ ⁨hours⁩ ago

        There is nothing difficult to grasp. They made rules then decided for no reason to let mercury break the rule. Why? Why not make mercury a dwarf planet instead of allowing it with no rule exception other than…just because.

        This is not bioligical… those MUST follow the rules. This was a traditional unscientific last… Exactly like constellations. Why not start removing stars from constellations because they are too far away? Except a couple of them just because.

        This IAU conference vote was not unanimous… it was very contentious and many wanted a more geological and broad definition rather than an earth centered definition that literally ONLY applies to our solar system. “Planets” can only exist around OUR Sun. Think about that.

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• mnemonicmonkeys@sh.itjust.works ⁨22⁩ ⁨hours⁩ ago

  And for neptune not clearing its orbit due to pluto crossing that orbit?

  Ah, yes. This is clearly justification for Pluto to become a planet! /s

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  • nexguy@lemmy.world ⁨22⁩ ⁨hours⁩ ago

    If the definition of a planet is that it has cleared is orbit then how is Neptune a planet? It shares its orbit with the dwarf planet pluto therefore they should both be dwarf planets correct?

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    • sp3ctr4l@lemmy.dbzer0.com ⁨21⁩ ⁨hours⁩ ago

      You could just look up the actual astronomical or mathematical definition of a ‘cleared orbit’ if you wanted to, you know that right?

      en.wikipedia.org/wiki/Clearing_the_neighbourhood

      As a consequence it does not then share its orbital region with other bodies of significant size, except for its own satellites, or other bodies governed by its own gravitational influence.

      This latter restriction excludes objects whose orbits may cross but that will never collide with each other due to orbital resonance, such as Jupiter and its trojans, Earth and 3753 Cruithne, or Neptune and the plutinos.[3]

      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.

      Pluto and other plutinos are bodies whose orbits are significantly governed by Neptune.

      Go look at all the numerical values provided by various algorithms that measure essentially the extent to which a celestial body is locally gravitationally dominant, the extent to which it has ‘cleared its orbit’.

      You may notice that everything considered a dwarft planet scores orders of magnitude less, by literally all the metrics.

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      • nexguy@lemmy.world ⁨21⁩ ⁨hours⁩ ago

        I understand the exception created for Neptune. But they had to create this exception… for their own brand new rule… in order to classify 8 things. Notice the exception is written very specifically just to keep pluto from “clearing” is orbit.

        Another IAU rule is that the body must assume hydrostatic equilibrium(nearly round). Mercury does NOT assume hydrostatic equilibrium. They knew this.

        Guess what? They just…decided…Mercury doesn’t have to follow that rule.

        It was all done very unscientifically.

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