> that is literally how scientific fields always approach arbitrary classifications.

That's a big overstatement. It's how some soft science fields sometimes do it. You can't get away with that in, say, physics and still end up with useful theories, because your theories quickly break down due to inconsistencies. You can't design working scientific theories by committee, because votes don't affect fundamental physical reality.

Much of astronomy is a hard science, which is why this definition came in for pushback even from astronomers themselves. Here's astronomer Phil Plait's take:

> "For some time now I, and many others, have stated that the IAU definition is silly for many reasons, including a line that says that planets can only orbit the Sun. If that’s true, then exoplanets — worlds orbiting other stars — aren’t really planets!" -- https://www.syfy.com/syfy-wire/mea-culpa-are-exoplanets-plan...

The article goes on to clarify that the IAU explicitly limited its definition to solar system planets - in fact, the resolution is titled ""Definition of a Planet in the Solar System."

As such, it's not even a universal scientific definition for "planet".

Another quote:

> "At [the IAU] 2006 international meeting in Prague, they drafted a series of defining characteristics for planets and put it to a vote. The definition passed, and the outcome was entirely predictable: They made things a lot worse."

> "...the more proximate problem is that these definitions are, um, silly."

-- https://www.syfy.com/syfy-wire/redefining-planets-answer-sea...

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Timon3 18 hours ago | parent [-]

> That's a big overstatement. It's how some soft science fields sometimes do it. You can't get away with that in, say, physics and still end up with useful theories,

Sorry, but this objection reveals that you either don't understand the topic of discussion at all, or you're arguing in bad faith. No theory in physics will break if you change the criteria of an arbitrary classification.

I'll pose the same challenge to you: please give me an example of what kind of definition for "planet" you'd be happy with. But remember, it must not take into account what we today consider "planets" to be.

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antonvs 15 hours ago | parent [-]

> Sorry, but this objection reveals that you either don't understand the topic of discussion at all, or you're arguing in bad faith.

Nice false dichotomy and binary thinking.

You're right that arbitrary classifications are arbitrary, obviously. My point is that you can't get away with arbitrary classifications in the context of hard science theories.

There's an example of a definition of "planet" in one of those Plait articles I linked:

> "A planet is a sub-stellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape adequately described by a triaxial ellipsoid regardless of its orbital parameters."

That comes from the following paper: https://www.hou.usra.edu/meetings/lpsc2017/pdf/1448.pdf

The Plait articles are worth reading, because they might help disabuse you of the notion that the IAU definition is a good one, and explain why it would make sense to have a better one.

	▲	Timon3 14 hours ago \| parent [-]
		> My point is that you can't get away with arbitrary classifications in the context of hard science theories. Arbitrary classifications don't factor into hard scientific theories, so I have no idea how this is relevant. Or what "hard science theory" are you thinking of that relies on whether we classify an object as a planet? We can modify arbitrary classifications without any theories being affected, because the theories don't rely on arbitrary classifications. We arbitrarily decided what "one meter" is, yet we use "meters" all over physics. We could change the definition of "one meter" tomorrow, and all our theories would stay valid, because they don't rely on arbitrary classifications. > There's an example of a definition of "planet" in one of those Plait articles I linked: >> "A planet is a sub-stellar mass body that has never undergone nuclear fusion and that has sufficient self-gravitation to assume a spheroidal shape adequately described by a triaxial ellipsoid regardless of its orbital parameters." How does one arrive at this definition, without taking into account what we today consider "planets" to be? What principle of physics tells you that a planet must be sub-stellar mass, or that it has never undergone nuclear fusion? You'll have to actually explain how this definition is any less arbitrary, but I don't think you'll be able to, because every useful definition falls under your objection.