Just bite the bullet and accept there are a lot of small planets in our solar system, or classify them based on size.
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#Dis... .
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."
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.
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.
(I'm by no means an expert, that's why I'm asking.)
I don't even.
I mean, I'm not unfamiliar with lame arguments, having presented many in the past. But this one...wow.
("That's Not A Moon...It's A Space Station!" tells us that those people long ago and far away didn't think that moon had to orbit a planet.)
To add more fun to the pile, is the "rogue planet" PSO J318.5-22 a planet? https://en.wikipedia.org/wiki/PSO_J318.5-22 . And yes, the IAU has already considered this case.
The point is it seems absurd that the past history of an object should matter, for this definition. Like if it's a big round object orbiting a star, it's a planet. It shouldn't matter how it got there. It seems quite possible there could be cases where another object clears the orbit of another object. Perhaps not aliens, but a rogue planet.
I was trying to recreate the "star trek test" argument that I heard a real astronomer use. He was upset with the new definition, and made an analogy to start trek. On the show they don't wait around for 12 months to observe the planet and any objects in its orbit, let alone it's past history. He argued that any sensible definition should be possible to determine immediately.
Of course we are arguing about the definition of a word, and all arguments are subjective and appeal to intuition. But still there can be bad definitions.
You seem to believe that if we cleared up those objects and dumped them into Earth's orbit, they would stay there.
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%20e...
"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.
Two modern examples of how "celestial objects" includes the Earth are https://www.iau.org/static/archives/releases/pdf/iau0915.pdf :
> Titan has long fascinated astronomers as the only moon known to possess a thick atmosphere, and as the only celestial body other than Earth to have stable pools of liquid on its surface.
and http://astroedu.iau.org/activities/blue-marble-floating-empt... :
> These astronauts were the first people to ever orbit a celestial body other than the Earth, ...
Now, three historical examples, the first from Youth's Book of Astronomy (1839), https://books.google.com/books?id=qZc-AQAAMAAJ&dq=celestial%...
> Their [the Chaldeans] ideas of the earth as a celestial body were also crude and imperfect.
The second from "A system of universal geography : or, A description of all the parts of the world, on a new plan, according to the great natural divisions of the globe, accompanied with analytical, synoptical, and elementary tables", vol. 1 (1847) at https://archive.org/stream/universalgeograp01maltuoft#page/n... :
> Theory of Geography. Of the Earth, considered as a celestial Body, and in its relations to the other celestial Bodies.
Since "considered as" isn't as strong as "is", here's the third example, from "Astronomy simplified" (1838), https://books.google.com/books?id=cWAEAAAAQAAJ&dq=celestial%...
> 5thly-That the Earth, like every other celestial body, moves with accelerated velocity during the perihelion, and ...
You are also right that "celestial body" in popular use is often treated as a synonym for "heavenly body". This is a pre-Copernican viewpoint, expressed in 1 Corinthians 15:40 as "There are also heavenly bodies and there are earthly bodies; but the splendor of the heavenly bodies is one kind, and the splendor of the earthly bodies is another."
However, you emphasized the technical definition, not the general culture use.
P.S. Did you mean "planets revolving around the Sun" instead of the Earth? Also, earlier you wrote "Earth, not being in the night sky, is not celestial", but I'll point out the Sun is also not in the night sky; is it also not celestial?