The moon was at one point molten, but that's not the same as saying it ever had a molten core. There's no evidence that I know of that it had a distinct core.
Why should I care how many entries there are under a good definition? I care about having a good definition.
Here's an example of a good definition:
A mass that has a single core, a well-defined gravitationally-shaped layered structure, that does not undergo nuclear fusion that formed within a star system.
Why is this good?
1. It's predictive. I have a hypothesis that can be falsified, that all objects of this type will behave in ways that all objects not of this type will not behave in.
2. It applies to extrasolar objects and rogue planets.
3. It is dependent only on intrinsic, not extrinsics. That makes the classification invariant unless the object itself is changed.
4. Science is not a democracy, it is a search for ever-greater understanding. Politics is a game for fools played by idiots.
5. The same definition has value and meaning whether you're a planetary scientist, geologist, cosmologist, colonist, miner or even astronomer. One definition to rule them all and in the darkness beat them over the head with a 2x4.
You may not agree with the definition, but this definition makes Pluto a planet and Eris, Vesta, Haumea and Makemake not planets.
1. It has liquid water 2. It has an evolving surface 3. Including atmosphere, it's larger than Earth
What we know about the Kuipier Belt
1. It has an Earth-sized "dwarf planet" (it's a dwarf because it hasn't cleared its orbit, even if it's the size of Jupiter), although Pluto is not that planet
I see nothing here that says "comet" or indeed anything that makes that relevant as to what class of object it is.
Should be fined to within an inch of their collective lives. There is no excuse for having a system vulnerable to phishing. Class III digital certificates and IPSec would be completely immune to phishing scams. Authentication via Kerberos would be beyond most teens.
Any member of staff that falls for phishing should be fired on the spot.
Any exam system that allows you to modify grades directly should be quietly buried in a landfill. A given answer gets a given mark. Actually, in the U.S., it's mostly multiple guess. The relative mark is thus fixed.
Only in countries with normalized grades for a region should allow the mean and standard deviation to be entered.
Excuses are reasonable, but whilst they can rationalize a grade, the grade is still the grade.
You're better off abandoning exams, but if you're going to have them then do it right.
This proves that in the new C standard, assert() should take two parameters. One for the assertion, one for the justification. (Ok, we call it the postcondition, but who's judging?)
Don't think Fred Hoyle wrote that. I made it quite clear what I had read and one of the greatest astrophysicists of the mid 20th century counts as a scientist.
Don't think the scientists who have developed brain-computer interfaces for artificial speech and artificial limbs (output) or artificial vision (input) would appreciate being told they were characters in a story. Feel free to tell them they're lying, to their face, in their laboratories. If I see reports of fighting breaking out in MIT or a major hospital, I'll know you did so. If I don't, it's because you chickened out after finding this stuff is real.
Of course there's a surface. For a start, you can't have gasses near the interior.
Secondly, the largest super-Earths known should be gas giants. All solar system formation models show these would have been planets similar to Saturn or Jupiter. Imagining Jupiter is a special case is... stupid.
Atmospheres are counted because they are physically part of the planet. Same reason the corona is part of the comet.
This isn't because I think it can't be done. Rather, it's because we are developing neural interfaces at about the same speed,
I'm going to borrow some ideas from Sir Fred Hoyle here.
First, in his novel The Black Cloud, his characters argue over whether an interstellar cloud would have one intelligence or many. They conclude that the latency would be so low and the interconnects of such high bandwidth that the distinction of one and many ceased to be meaningful.
This will apply to AI. The brain-computer interfaces will be so advanced by the time strong AI becomes possible that the distinction between one and many won't apply. Any given AI and all the humans linked to it will become a single intelligence with multiple avatars. Because humans are reluctant to give up individuality, I suspect it'll be one AI linked to one person at any given time.
There will be no conflict between machines and people because there will be no distinction.
One reason I think this a plausible scenario, in addition to Hoyle, is that it eliminates the whole phobia of technology. The machines don't run anything, we do because we are the machines. Another is because of Hoyle's other prediction, in Ossian's Ride, that we might not find alien philosophy palatable.
I would agree, if it made it too broad. That's why I've been talking about plotting out the different objects and letting them self-group.
However, can we come up with a strict definition that is useful and predictive (a key requirement in science)?
What do we know?
We know that all asteroids are fairly homogeneous and divide into two groups - rubble piles and cohesive undifferentiated structures. In either case, they are not stratified. They have no atmosphere. They are evaporating under the solar winds. They have no cores. They're incapable of supporting any liquid. None of them have an atmosphere. They have never been geologically active. No magnetic field, past or present.
We know that all comets have multiple small asteroids in them, encased in a mix of ice and organics. We can regard each of these asteroids as a core, as clearly the ice condensed around a cluster of objects that remained in close proximity through gravity. They evaporate when in close proximity to the sun. They are capable of supporting liquid when evaporating. They cannot retain an atmosphere, but the corona could be classed as a temporary atmosphere. It's very basic, though, and unstructured. The photographs from the lander (the rock piles) and data from Galileo indicate they have some geological activity, but that's kind of obvious. No magnetic field, past or present.
Mercury has a single liquid core and a magnetic field. Current evidence is that there has been geological activity and it may still be active. It is highly stratified. It doesn't seem to lose much material, but it's hard to say how much it gains. Since it has a liquid core, obviously there are liquids.
Venus has a single liquid core and a magnetic field. It's intensely active. Most of the planet is liquid. It replaces the crust completely every few decades. The atmosphere is structured, thick, hot and oppressive. Reminds me of Kuro5hin, apart from the structured bit. What it reminds other people of shall remain PG-13, please.
Earth fits the same pattern. So does Mars, although its geology is mostly dead. It's hard to talk about the geology of the gas giants, but they fit the same pattern otherwise and the atmospheres evolve at a ferocious pace. (In all probability, the gas giants have a core similar to Earth's - liquid surrounding a solid mass.) We don't know much about Neptune, but everything we know fits the pattern.
Pluto, the only TNO with an atmosphere, liquid water, a liquid core, stratification and an active geology. The atmosphere mirrors that on Mars. Again, it is highly structured. Therefore it structurally and geologically resembles established planets, so we don't have to extend any definitions to include it. Going by the physical and geological properties, then, it is a planet.
Ceres does not fit this. Vesta might, in part. None of the planetary masses found further out do, although if there's an Earth-sized planet in the belt it probably would. (It's currently thought that such a planet exists, as Pluto can't explain Neptune's orbit perturbation.) And that's the problem. By the IAU's definition, an Earth-sized body that's a KBO is a dwarf planet, even though it's the same size as Earth. By the above differential diagnosis, however, size doesn't matter. It's what the object did with it. Such a thing could, therefore, be a planet.
A red giant is a star that exists at point Y along the main sequence. The sun as it is now is a star that exists at point X along the main sequence.
Astronomers with any sense call the sun a main sequence star. Everything else is ephemera.They may include that ephemera, such as element ratios, temperature, diameter, etc, because that defines where along the curve the sun is. But its core classification is invariant. And that is critical.
The ephemera is invariant of space - it doesn't matter where the sun is, you could teleport it to the other side of the universe and it would continue to have the same element ratios, temperature and diameter. They are invariant of the observer - all observers would agree on the same values, after relativistic effects are considered.
They are not invariant with time because they vary with time. However, and this is critical, they vary according to a clear predictive model. A model that can be falsified. A model, not to put too fine a point on it, that is actually scientific. They therefore do not vary randomly.
Do you see how critical this is? Here, we have a classification that selects a model, and a state space that selects where we are on the model. We can then use that model to say what the next state space will be.
How the hell are we supposed to do that with the IAU's definitions?
According to the IAU definition, if Earth were to be launched outside of the solar system, it would be classed as a star. A brown dwarf. What the hell are we supposed to do with that? If Jupiter also did, it would also become a brown dwarf. They'd not be classed as distinct but the same. How is that useful? What model do we apply that will work for both?
Pluto has a liquid core, has liquid water, has active geology and an atmosphere. And we're supposed to use the same model for it as we would for Ceres, which has none of those properties? How is that useful? How is that predictive?
Ceres has no active geology, Pluto does. Ceres has no core, Pluto not only does but it's liquid. Ceres is evaporating, Pluto isn't. Ceres is homogenous, Pluto is stratified. Ceres is basically a lump of rock with some ices congealed on, Pluto has liquid water. Ceres is inert, Pluto is evolving.
Now, tell me which one best matches Earth or Mars?
Let's see how Jupiter compares.
Active geology? Doesn't really apply, but it is certainly active. Core? Yes. At those pressures, it's more likely liquid surrounding a solid core, which is the arrangement on Earth. It's definitely not evaporating. We've sent probes in and it's definitely stratified. It's definitely gas, liquid and solid. It's certainly evolving. What's the core size? Mass-wise, it must exceed Earth by about 1.2x. as the rocky exoplanet found of that mass is regarded as originally a Jupiter-sized gas giant that has lost its atmosphere. A similar rocky planet will exist at the heart of all gas giants.
Conclusion, Jupiter is quite definitely a planet.
Ok, but here we're measuring the atmosphere, as we did for Earth, as part of the size. What does this do to the diameter of Ceres? Doesn't have one, so doesn't change anything.
What about Pluto? Pluto is the only trans-Neptunian object with a known atmosphere. (Interesting.) In some aspects it resembles even the atmosphere of Mars. (Doubly interesting. So the atmosphere closely resembles a known planet. Hmmm) New Horizons discovered in the atmosphere of Pluto a multi-layered haze, which covers the entirety of the dwarf planet and reaches altitude over 200 km. (So it's a stratified atmosphere.) The full diameter of Pluto's atmosphere, according to JPL, exceeds that of Earth, so if you are regarding atmosphere as part of the planet then Pluto is technically bigger than Earth.
So with Pluto, we continue to have this complex, structured, organized body that could be considered larger than Earth if atmospheres are to be considered.
I see nothing inconsistent with this model, I see plenty that allows for predictive modeling and plenty that is space and time invariant.
Ad that is why botany is a humanity and not a science. You can't predict anything with a definition like that. It's also why geneticists have been throwing out most of the botanical taxa and replacing them with a much more rigorous system.
All I want is for the same to be applied to physical objects in space.
From a software standpoint, a failure to validate inputs and a failure to validate code against a specification is independent of what the code does.
In ISO 9000 training, we were taught that we should consider anything that could cost $1m or more if things went wrong to be equivalent to killing someone. But, hey, what does NASA know about failure not being an option?
Your definitions still don't take into consideration the need by scientists for definitions that categorise in ways useful to planetary scientists.
They're not interested in whether the planet count is single digit in a given number base.
They care that if you plot the properties of all the objects in the solar system and apply the categorisations, all of the properties and models group perfectly within those categories and that you can falsify a prediction.
They also care that categories are invariant and independent of externals. An object with a given set of properties will have a given category, no matter what.
That means a planet identical to Earth orbiting a Super Jupiter should be a planet. It would also be a moon. A moon is a description of a relationship, not a description of an object.
It means a Super Earth that is a rogue planet is never classed as a brown dwarf star.
It means that if a Super Earth was found in the Kuipier Belt, it can't be a Dwarf Planet.
What is do wrong with that?
It can be done. There are ways to define a planet that have nothing to do with position, relationship or other extrinsics, or with mass or diameter. None of these properties relate to the actual structure, physics, geology or nature of the object.
If you use those four properties, though, you'd have a very decent intrinsic rather than extrinsic definition. Something that would be useful.
Which was indeed the case 250 million years ago. So the moon was a planet in the relatively recent past. Which means the Earth did not clear its orbit, the moon did.
You can either have a valid definition and see what that gets you, or you can have a contrived definition arranged to fit a preconceived fact.
I do not encourage being insensibly drawn to fitting facts to theories.
Should we define a particle specifically to exclude electrons? Would that be useful or useless?
Who cares how large things are? Where is that a useful property to measure?
The only properties that matter are the properties that are invariant in a category and linearly separate themselves from another category.
Think dichotomous key that holds true for all exoplanets and rogue planets, that is based on fundamental properties that can be used in planetary science.
If that means there are only 3 planets, 33 or 333, who the hell cares? Reality is what it is, it is not a democracy and it doesn't give a shit whether you like it or not.
I don't believe in scientific notation designed to limit a group to X. Either the definition is based on sound science or it is crap.
Pluto is structurally utterly unlike Ceres or any KBO, therefore it is not in the same category as those.
Pluto is structurally the same as Earth and Mars, therefore that is the category it belongs in.
Reality is not a popularity contest, I do not give a flying who thinks Pluto is what, it is structurally the same as a planet and is structurally distinct from anything not a planet. Far as I'm concerned, planetary science overrules any ego. The science comes first.
Slashdot Mirror
The moon was at one point molten, but that's not the same as saying it ever had a molten core. There's no evidence that I know of that it had a distinct core.
Why should I care how many entries there are under a good definition? I care about having a good definition.
Here's an example of a good definition:
A mass that has a single core, a well-defined gravitationally-shaped layered structure, that does not undergo nuclear fusion that formed within a star system.
Why is this good?
1. It's predictive. I have a hypothesis that can be falsified, that all objects of this type will behave in ways that all objects not of this type will not behave in.
2. It applies to extrasolar objects and rogue planets.
3. It is dependent only on intrinsic, not extrinsics. That makes the classification invariant unless the object itself is changed.
4. Science is not a democracy, it is a search for ever-greater understanding. Politics is a game for fools played by idiots.
5. The same definition has value and meaning whether you're a planetary scientist, geologist, cosmologist, colonist, miner or even astronomer. One definition to rule them all and in the darkness beat them over the head with a 2x4.
You may not agree with the definition, but this definition makes Pluto a planet and Eris, Vesta, Haumea and Makemake not planets.
1. It has liquid water
2. It has an evolving surface
3. Including atmosphere, it's larger than Earth
What we know about the Kuipier Belt
1. It has an Earth-sized "dwarf planet" (it's a dwarf because it hasn't cleared its orbit, even if it's the size of Jupiter), although Pluto is not that planet
I see nothing here that says "comet" or indeed anything that makes that relevant as to what class of object it is.
Should be fined to within an inch of their collective lives. There is no excuse for having a system vulnerable to phishing. Class III digital certificates and IPSec would be completely immune to phishing scams. Authentication via Kerberos would be beyond most teens.
Any member of staff that falls for phishing should be fired on the spot.
Any exam system that allows you to modify grades directly should be quietly buried in a landfill. A given answer gets a given mark. Actually, in the U.S., it's mostly multiple guess. The relative mark is thus fixed.
Only in countries with normalized grades for a region should allow the mean and standard deviation to be entered.
Excuses are reasonable, but whilst they can rationalize a grade, the grade is still the grade.
You're better off abandoning exams, but if you're going to have them then do it right.
The FTC takes backhanded. We know that, that's what led to net neutrality (Title 2) being revoked illegally.
SCOTUS has ruled many times that commercial speech doesn't get full 1A protection. This is commercial speech. Problem solved.
For more problem solving, please call this number...
This proves that in the new C standard, assert() should take two parameters. One for the assertion, one for the justification. (Ok, we call it the postcondition, but who's judging?)
Efficiency isn't guilt, it's intelligent. Racism and bigotry are inefficient and stupid.
(Ok, to be fair, most racism is due to brain abnormalities leading to subnormal intelligence, it's not their fault.)
Don't think Fred Hoyle wrote that. I made it quite clear what I had read and one of the greatest astrophysicists of the mid 20th century counts as a scientist.
Don't think the scientists who have developed brain-computer interfaces for artificial speech and artificial limbs (output) or artificial vision (input) would appreciate being told they were characters in a story. Feel free to tell them they're lying, to their face, in their laboratories. If I see reports of fighting breaking out in MIT or a major hospital, I'll know you did so. If I don't, it's because you chickened out after finding this stuff is real.
Of course there's a surface. For a start, you can't have gasses near the interior.
Secondly, the largest super-Earths known should be gas giants. All solar system formation models show these would have been planets similar to Saturn or Jupiter. Imagining Jupiter is a special case is... stupid.
Atmospheres are counted because they are physically part of the planet. Same reason the corona is part of the comet.
Sorry, this is established stuff.
We count the atmosphere of Earth and Jupiter. Include the atmosphere on Pluto and it's bigger than Earth.
The AC got everything wrong, New Horizons established a lot of things.
This isn't because I think it can't be done. Rather, it's because we are developing neural interfaces at about the same speed,
I'm going to borrow some ideas from Sir Fred Hoyle here.
First, in his novel The Black Cloud, his characters argue over whether an interstellar cloud would have one intelligence or many. They conclude that the latency would be so low and the interconnects of such high bandwidth that the distinction of one and many ceased to be meaningful.
This will apply to AI. The brain-computer interfaces will be so advanced by the time strong AI becomes possible that the distinction between one and many won't apply. Any given AI and all the humans linked to it will become a single intelligence with multiple avatars. Because humans are reluctant to give up individuality, I suspect it'll be one AI linked to one person at any given time.
There will be no conflict between machines and people because there will be no distinction.
One reason I think this a plausible scenario, in addition to Hoyle, is that it eliminates the whole phobia of technology. The machines don't run anything, we do because we are the machines. Another is because of Hoyle's other prediction, in Ossian's Ride, that we might not find alien philosophy palatable.
I would agree, if it made it too broad. That's why I've been talking about plotting out the different objects and letting them self-group.
However, can we come up with a strict definition that is useful and predictive (a key requirement in science)?
What do we know?
We know that all asteroids are fairly homogeneous and divide into two groups - rubble piles and cohesive undifferentiated structures. In either case, they are not stratified. They have no atmosphere. They are evaporating under the solar winds. They have no cores. They're incapable of supporting any liquid. None of them have an atmosphere. They have never been geologically active. No magnetic field, past or present.
We know that all comets have multiple small asteroids in them, encased in a mix of ice and organics. We can regard each of these asteroids as a core, as clearly the ice condensed around a cluster of objects that remained in close proximity through gravity. They evaporate when in close proximity to the sun. They are capable of supporting liquid when evaporating. They cannot retain an atmosphere, but the corona could be classed as a temporary atmosphere. It's very basic, though, and unstructured. The photographs from the lander (the rock piles) and data from Galileo indicate they have some geological activity, but that's kind of obvious. No magnetic field, past or present.
Mercury has a single liquid core and a magnetic field. Current evidence is that there has been geological activity and it may still be active. It is highly stratified. It doesn't seem to lose much material, but it's hard to say how much it gains. Since it has a liquid core, obviously there are liquids.
Venus has a single liquid core and a magnetic field. It's intensely active. Most of the planet is liquid. It replaces the crust completely every few decades. The atmosphere is structured, thick, hot and oppressive. Reminds me of Kuro5hin, apart from the structured bit. What it reminds other people of shall remain PG-13, please.
Earth fits the same pattern. So does Mars, although its geology is mostly dead. It's hard to talk about the geology of the gas giants, but they fit the same pattern otherwise and the atmospheres evolve at a ferocious pace. (In all probability, the gas giants have a core similar to Earth's - liquid surrounding a solid mass.) We don't know much about Neptune, but everything we know fits the pattern.
Pluto, the only TNO with an atmosphere, liquid water, a liquid core, stratification and an active geology. The atmosphere mirrors that on Mars. Again, it is highly structured. Therefore it structurally and geologically resembles established planets, so we don't have to extend any definitions to include it. Going by the physical and geological properties, then, it is a planet.
Ceres does not fit this. Vesta might, in part. None of the planetary masses found further out do, although if there's an Earth-sized planet in the belt it probably would. (It's currently thought that such a planet exists, as Pluto can't explain Neptune's orbit perturbation.) And that's the problem. By the IAU's definition, an Earth-sized body that's a KBO is a dwarf planet, even though it's the same size as Earth. By the above differential diagnosis, however, size doesn't matter. It's what the object did with it. Such a thing could, therefore, be a planet.
A red giant is a star that exists at point Y along the main sequence. The sun as it is now is a star that exists at point X along the main sequence.
Astronomers with any sense call the sun a main sequence star. Everything else is ephemera.They may include that ephemera, such as element ratios, temperature, diameter, etc, because that defines where along the curve the sun is. But its core classification is invariant. And that is critical.
The ephemera is invariant of space - it doesn't matter where the sun is, you could teleport it to the other side of the universe and it would continue to have the same element ratios, temperature and diameter. They are invariant of the observer - all observers would agree on the same values, after relativistic effects are considered.
They are not invariant with time because they vary with time. However, and this is critical, they vary according to a clear predictive model. A model that can be falsified. A model, not to put too fine a point on it, that is actually scientific. They therefore do not vary randomly.
Do you see how critical this is? Here, we have a classification that selects a model, and a state space that selects where we are on the model. We can then use that model to say what the next state space will be.
How the hell are we supposed to do that with the IAU's definitions?
According to the IAU definition, if Earth were to be launched outside of the solar system, it would be classed as a star. A brown dwarf. What the hell are we supposed to do with that? If Jupiter also did, it would also become a brown dwarf. They'd not be classed as distinct but the same. How is that useful? What model do we apply that will work for both?
Pluto has a liquid core, has liquid water, has active geology and an atmosphere. And we're supposed to use the same model for it as we would for Ceres, which has none of those properties? How is that useful? How is that predictive?
Ceres has no active geology, Pluto does. Ceres has no core, Pluto not only does but it's liquid. Ceres is evaporating, Pluto isn't. Ceres is homogenous, Pluto is stratified. Ceres is basically a lump of rock with some ices congealed on, Pluto has liquid water. Ceres is inert, Pluto is evolving.
Now, tell me which one best matches Earth or Mars?
Let's see how Jupiter compares.
Active geology? Doesn't really apply, but it is certainly active. Core? Yes. At those pressures, it's more likely liquid surrounding a solid core, which is the arrangement on Earth. It's definitely not evaporating. We've sent probes in and it's definitely stratified. It's definitely gas, liquid and solid. It's certainly evolving. What's the core size? Mass-wise, it must exceed Earth by about 1.2x. as the rocky exoplanet found of that mass is regarded as originally a Jupiter-sized gas giant that has lost its atmosphere. A similar rocky planet will exist at the heart of all gas giants.
Conclusion, Jupiter is quite definitely a planet.
Ok, but here we're measuring the atmosphere, as we did for Earth, as part of the size. What does this do to the diameter of Ceres? Doesn't have one, so doesn't change anything.
What about Pluto? Pluto is the only trans-Neptunian object with a known atmosphere. (Interesting.) In some aspects it resembles even the atmosphere of Mars. (Doubly interesting. So the atmosphere closely resembles a known planet. Hmmm) New Horizons discovered in the atmosphere of Pluto a multi-layered haze, which covers the entirety of the dwarf planet and reaches altitude over 200 km. (So it's a stratified atmosphere.) The full diameter of Pluto's atmosphere, according to JPL, exceeds that of Earth, so if you are regarding atmosphere as part of the planet then Pluto is technically bigger than Earth.
So with Pluto, we continue to have this complex, structured, organized body that could be considered larger than Earth if atmospheres are to be considered.
I see nothing inconsistent with this model, I see plenty that allows for predictive modeling and plenty that is space and time invariant.
Ad that is why botany is a humanity and not a science. You can't predict anything with a definition like that. It's also why geneticists have been throwing out most of the botanical taxa and replacing them with a much more rigorous system.
All I want is for the same to be applied to physical objects in space.
Pluto is layered, for a start. Ceres is much more homogeneous.
Pluto has liquid water and a liquid core. Ceres has no liquid water and has no core at all.
Pluto is stable, Ceres is slowly evaporating in the solar winds.
Pluto has an active geology, Ceres does not.
Will this suffice or should I add more?
From a software standpoint, a failure to validate inputs and a failure to validate code against a specification is independent of what the code does.
In ISO 9000 training, we were taught that we should consider anything that could cost $1m or more if things went wrong to be equivalent to killing someone. But, hey, what does NASA know about failure not being an option?
Your solution to #1 doesn't solve rogue planets.
Your definitions still don't take into consideration the need by scientists for definitions that categorise in ways useful to planetary scientists.
They're not interested in whether the planet count is single digit in a given number base.
They care that if you plot the properties of all the objects in the solar system and apply the categorisations, all of the properties and models group perfectly within those categories and that you can falsify a prediction.
They also care that categories are invariant and independent of externals. An object with a given set of properties will have a given category, no matter what.
That means a planet identical to Earth orbiting a Super Jupiter should be a planet. It would also be a moon. A moon is a description of a relationship, not a description of an object.
It means a Super Earth that is a rogue planet is never classed as a brown dwarf star.
It means that if a Super Earth was found in the Kuipier Belt, it can't be a Dwarf Planet.
What is do wrong with that?
It can be done. There are ways to define a planet that have nothing to do with position, relationship or other extrinsics, or with mass or diameter. None of these properties relate to the actual structure, physics, geology or nature of the object.
If you use those four properties, though, you'd have a very decent intrinsic rather than extrinsic definition. Something that would be useful.
Which was indeed the case 250 million years ago. So the moon was a planet in the relatively recent past. Which means the Earth did not clear its orbit, the moon did.
It is if you're a planetary scientist. If you don't know what is a planet and what isn't, you can't model either.
You can either have a valid definition and see what that gets you, or you can have a contrived definition arranged to fit a preconceived fact.
I do not encourage being insensibly drawn to fitting facts to theories.
Should we define a particle specifically to exclude electrons? Would that be useful or useless?
Who cares how large things are? Where is that a useful property to measure?
The only properties that matter are the properties that are invariant in a category and linearly separate themselves from another category.
Think dichotomous key that holds true for all exoplanets and rogue planets, that is based on fundamental properties that can be used in planetary science.
If that means there are only 3 planets, 33 or 333, who the hell cares? Reality is what it is, it is not a democracy and it doesn't give a shit whether you like it or not.
That would mean a planet ejected be the star becomes a brown dwarf star (as per current definition) and turns back into a planet on recapture.
Dunno about you, but I'm a little unhappy with this planet-star duality depending on where it is.
Rule number one in science is that things should be space-invariant and time-invariant. This is clearly neither.
The moon is large enough that the Earth and moon are considered a binary planet.
I don't believe in scientific notation designed to limit a group to X. Either the definition is based on sound science or it is crap.
Pluto is structurally utterly unlike Ceres or any KBO, therefore it is not in the same category as those.
Pluto is structurally the same as Earth and Mars, therefore that is the category it belongs in.
Reality is not a popularity contest, I do not give a flying who thinks Pluto is what, it is structurally the same as a planet and is structurally distinct from anything not a planet. Far as I'm concerned, planetary science overrules any ego. The science comes first.
Any problem with that?