Earth is a ‘dwarf planet’ because it has not cleared its orbit | Hacker News Reader

Earth is a ‘dwarf planet’ because it has not cleared its orbit

medium.com

104 pointsrbanffy50 comments

This is very misleading, and it looks to be intentionally so. The author pretends that "cleared its orbit" means "cannot share its orbit with any sort of rock". But that's not at all how "cleared its orbit" is defined.

The excellent Wikipedia page [1] on what "cleared its orbit" really means should tell you enough. Firstly, this asteroid would be several magnitudes below the amount of mass necessary to strip Earth from its status. Secondly, due to this body being in orbital resonance with Earth its mass would not even count towards the mass that Earth has not cleared out of its orbit. This also counts for 3753 Cruithne, one of Earth's other known co-orbitals [2] which we've known about for years without making a fuzz, also because it has insignificant mass and is in orbital resonance.

Given the tone of the article and how easily it can be falsified, it seems to me the author is deliberately misleading his audience to push his nostalgia for Pluto's planethood.

[1]: https://en.wikipedia.org/wiki/Clearing_the_neighbourhood

[2]: https://en.wikipedia.org/wiki/Quasi-satellite#Earth

This is either a clickbait article or a weak April Fools' joke.

The date on the Medium article is Mar 21.

It's weird someone can can get so worked up that they use the term "outrage" (apparently seriously) for an atronomical re-definition.

Regardless of the validity of the premise, the conclusion—and the point—of the article is valid. Debating over the definition of planets is silly. It feels as if this is done just so school children can pass astronomy tests by residing the names of all 8 planets. Otherwise there is no point in holding this definition, or any definition for that matter.

It is a known problem classifying most natural phenomena is at best difficult—but most likely impossible—to do so under a simple definition. What most naturalists do is to holding a set of common beliefs over what belongs in which category. For example, there is no easy definition of a bird. Rather we have a set of common beliefs over which animals can rightly be called a bird. Worse, the set of “common beliefs” varies depending on field of interests. Some people might talk about viruses as “living” because that servers their purpose (it makes their work easier; it makes more sense) while other wont.

I hope that we soon stop this silly debate. Our definition of a planet will not hold for long. The more planets we discover the weaker the current definition will become (this is the authors point). When that happens I bet people will talk about Pluto (and Eris, Sedna, etc.) as a planet just because it matches peoples idea of what a planet is. Just like people talk about viruses as living organisms just because it fits nicely into what we think life is.

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edit: grammar

There are a multitude of objective measures that can be applied to planet classification. In almost all of them, Pluto is an obvious outlier. The controversy hype was manufactured by the press looking for a sensation.

The same can be said about birds. You can say that for an animal to be considered a bird it: a) has to have feathers, b) has to have warm blood, c) cannot have claws on its wings, d) cannot have teeth. But than you find one animals that we can all agree is a bird that has claws on its wings while still a chick (will it grow up to become a bird?).

So you use a new definition. Bird are evolutionary descendant some reptiles had contained feathers and warm blood. This will (mostly) hold out until we discover some extinct groups of reptiles that had feathers and warm blood.

Note though how vague the latter definition is. It has to be. Because we cannot derive at a solid definition of a bird that encapsulates all animals that we can consent on calling a bird.

Except bird is not the scientific name it's Ornithurae which nobody cares about. Planet on the other hand is from Astronomy (asteres planetai), so just as Ornithurae means what scientists agree it means so does Planet. Electron and planet are both in common useage, but nobody gets in a tizzy about it.

PS: This is just pure bike-shedding by people who only care about the trivia and don't really use it for anything meaningful.

If you think that the blog's point was to openly discuss the arbitrarity of certain definitions, then you have read another blog than I did. Given the blog's obvious agenda, I find it a bit disingenious to summarize it like you do.

The new definition of 'planet' is meant to capture the set of bodies that are the most significant, dominant or prominent bodies in the Solar System. And under the current definition, this is captured perfectly, and will work well in the Solar System for the next billion years at least. While I agree that the definition is not perfect and ultimately arbitrary, our categorization of things should be helpful. Given their vastly different influence on the Solar System, a categorization in which Venus and Jupiter are distinct from Sedna and Ceres is more helpful than one in which they are the same, in my opinion.

> [...] and the intuition we all have that Pluto, is in fact, a planet.

It's not intuition, it's rote learning. Nobody cares if Eris is a planet or not, because nobody memorized a list of planets that include Eris.

Eris is (apparently) slightly smaller than Pluto, but (apparently) the mass is slightly bigger. So in any sane classification both are planets or neither.

The problem is that we don't know how many other object of similar size and mass are out there. They are very difficult to detect, so probably there are a few more to be discovered.

Assumed it was an April Fool's joke until I looked at the date of the article.

Eris is slightly smaller but more massive than Pluto. The discovery of Eris lead to the reconsideration of the definition of a planet.

There's a choice to be made, either Pluto, Eris, Haumea, Makemake and Ceres are all planets or none of them are. And any new discoveries will be planets too. Or we come up with some kind of non-scientific arbitrary choice that Pluto is a planet because people on the internet got mad when it was changed to a dwarf planet.

Out of the dwarf planets, Ceres is my favorite because of the ingenious mathematics that lead to the determination of its orbit and thus verified that it's a planet. There was only a week's worth of observations before the planet went behind the sun and Carl Friedrich Gauss invented a method for initial orbit determination from three observations and pioneered the method of least squares to further refine the orbit to match the rest of the observations and the planet appeared where predicted a year later.

At the time of discovery in 1801, Ceres was considered to be the 8th planet (Neptune wouldn't be discovered for another 70 years). I don't know what eventually caused Ceres to be demoted from its planet status (perhaps because it's in the middle of the asteroid belt).

I think that dwarf planet is a suitable label to give Pluto. It's an insignificant blot of dirt in the outer solar system, and there are probably dozens like it waiting to be discovered.

The first four asteroids, Ceres, Pallas, Juno, and Vesta, were considered planets until the 1850s when lots more asteroids were discovered. https://en.wikipedia.org/wiki/Ceres_(dwarf_planet)#Classific...

> There's a choice to be made, either Pluto, Eris, Haumea, Makemake and Ceres are all planets or none of them are.

This is half true. We don't strictly need a clear definition of a natural phenomena. Just look at the trouble we are having defining life. In fact, it might prove to be impossible to derive a solid definition. Yet most of us agree that all animals are living organisms, but fire isn't.

In my view Pluto, Eris, Haumea, Makemake, etc. are all planets. Just because they fit my idea of what a planet is. I am less keen on grouping Ceres with them (but the reason is that I was raised knowing that it was an asteroid, so I am willing to reconsider). If voyager 1 stumbles upon an earth size spherical body in (say) 50 years, I will want to consider it a (rouge) planet, even though it is missing some criteria for the current definition. We can indeed call Pluto a planet and Ceres an asteroid. That is only consistent with how we treat most other categories of natural phenomena.

I like to think of the entire asteroid belt as a failed planet.

>It's not intuition, it's rote learning. Nobody cares if Eris is a planet or not, because nobody memorized a list of planets that include Eris.

Couldn't have put it better. The author seems scientific or at least highly educated himself, so it's strange that he cares what we feel should be a planet.

First they came for the Kuiper belt objects, and I said nothing because I do not live on a Kuiper belt object...

This reads like an impassioned argument made by someone who doesn't really know what he's talking about.

Scientists need to come up with terms for groups of things to help the process of understanding them and communicating about them. If you're not a scientist and want to call Pluto a planet or Earth a moon or the Moon a star or Uranus a black hole -- I guess go for it, but recognize that it'll make having conversations with learned people about those things more difficult.

It's like getting into an argument about whether an iPhone becomes a desktop computer when you use it while it sits on your desk. Fine. Call it a desktop computer, but you're just going to confuse everyone. "Yeah, you can only use [Software X] on your desktop computer." "I tried but it totally didn't work!" "What's your operating system?" "iOS." "That's not a desktop computer." "But it's right here on my desk."

And scene.

I love how the author accuses the IAU of an agenda, but then clearly has his own--which doesn't seem to be nearly as grounded in taxonomic consistency.

I think part of the author's goal is pointing out that taxonomic consistency is useless if you're using stupid criteria, and then arguing that the criteria are stupid.

The second point is arguable, the first is not.

> I think part of the author's goal is pointing out that taxonomic consistency is useless if you're using stupid criteria

Of course that falls down when the author is either misunderstanding or misrepresenting the criteria.

This is only even a theoretical issue if 2016 H03 is both in a long term Earth grazing orbit and is not gravitationally bound to it.

If it's only in a temporary orbital relationship with Earth on a geological timescale, then it will eventually be cleared. If it's gravitationally bound to Earth then it's just in an odd kind of orbit.

No, clear it's orbit relative to similarly sized objects. The earth is more than 10^10 times as large so it's in no way comparable. It's like saying you don't live alone because there are single cell organisms in your house.

Pluto is less than 1/500th Neptune's mass, like having a rat living in your house.

Using this article's logic, Jupiter is not a planet either (it has two swarms of asteroids hanging out around its L4 and L5 lagrange points).

Theyre gravitationally bound to Jupiter.

If pluto becomes a planet again michael brown gets to write a new book called 'If I had killed pluto this is how I would have done it'

This is kind of silly... this is really a problem with the human obsession with creating taxonomies and classifications of natural phenomena, when natural phenomena are basically collections of atoms that have very fuzzy boundaries. Clustering algorithms are, in general, very subjective, and it's no surprise that our scientific efforts to "cluster" everything often produce counter-intuitive or undesirable results at certain boundary cases.

It's the same problem with biological taxonomies - is a lungfish a fish or an amphibian? The reality is it doesn't matter apart from the artificial taxonomy we impose on it so that our brains can better cope with the complexity of the Universe.

Perhaps a better (but more annoying) way of classifying everything would be to use hierarchically clustered taxonomies for everything, so that we could make statements like "Earth is considered a planet if we cut the dendrogram at level 5, but a dwarf planet if we cut at level 4, etc".

I completely agree. It's so silly that I chuckle every time this argument comes up. Then again, people are so attached to their definitions and classifications in a way that it becomes part of how they define themselves, and therefore any suggested change is considered a personal threat. This of course is not limited to planets...

This was interesting. If I am understanding correctly by the same "rules" pluto was determined to not be a planet it now would apply to earth.

Quote from article "Asteroid 2016 H03 is proof that Earth has not cleared the neighborhood around its orbit. Therefore, under the definition of a planet vigorously defended by the IAU since the adoption of Resolution 5A on August 24, 2006, Earth is a ‘dwarf planet’ because it has not cleared its orbit, which is the only criteria of their definition that Pluto fails."

"what planet are you on?.....trick question,you are not on a planet, youre on a dwarf planet:)"

No, this was written by someone who is sad about the redefinition of planet, and so wrote this mis-leading piece about what constitutes clearing an orbit. Jupiter, for example, has 100,000 trojan asteroids in it's orbit.

https://en.wikipedia.org/wiki/Clearing_the_neighbourhood

I don't think the definition is clear, but one asteroid ain't it. I do like the idea of uberplanets.

How is he even pretending? The definition (as I recall and on wiki) is clearly about comparable sized objects, and 100m vs 13,000,000m isn't very comparable.

I don't see a discussion of the actual technical definition. Only bad semantics.

Wikipedia, in brief: "In the end stages of planet formation, a planet will have "cleared the neighbourhood" of its own orbital zone, meaning it has become gravitationally dominant, and there are no other bodies of comparable size other than its satellites or those otherwise under its gravitational influence."

Note that this definition has to make an allowance for Earth, because our moon is "of comparable size" by some definitions, but it is also under Earth's influence. (Pluto and its moon co-orbit a point beyond the surface of Pluto so if Pluto is a planet why not Charon)

I'll never not be amused by how salty people get over Pluto being stripped of its planet-hood.

"Planet" is a word. I have no intuition for what a "planet" is because I was not born knowing English.

However, it seems intuitively true to me that Jupiter, Saturn, Uranus, and Neptune are different sorts of things, whatever you want to call them, than Mercury, Venus, Earth, Mars; that our moon is a different sort of thing from all of those (and more like the moons of all of those); and that Pluto is probably closer to Mercury-Mars than to the moon, or Eris, or Ceres, or anything else.

If you tell me that the appropriate label for Jupiter-Neptune is "planet" and for Mercury-Mars, Pluto, and Eris is "dwarf planet," I'll accept that; those sound like good categories. If you tell me that the appropriate label for Mercury-Neptune is "orbinaut" and the appropriate label for Pluto and Eris is "astrolith," I'll accept that too, those also sound like good categories. I have no intuitive objection to either of those categorizations, and both seem like they could be supported by evidence.

If you tell me that Mercury, Earth, Jupiter, Uranus, and Pluto are "oddballs" and the rest are "evenballs," that seems intuitively wrong. But I don't think anyone's proposing that!

The terms are gas giant and terrestrial (or rocky) planet. They're already there.

The point about extrasolar planets is great. Technically we can't say we discovered an extrasolar planet because it's impossible to ascertain it has cleared its neighborhood. It could easily be a dwarf planet.

"Planet" refers to points of light that have complex motion in the night sky throughout the year. Earth is below the sky, therefore Earth cannot possibly be a planet. This is just common sense people.

I am absolutely amazed by how many people have such a strong sentimental attachment to Pluto. Forget about the clearing orbit requirement, even though this article puts up very fallacious arguments, and instead considered that Pluto is smaller than Mercury. Pluto is smaller than our moon. Pluto is not even as wide as Asia. Pluto and Charon orbit a point outside Pluto's surface.

Oh, and then there's the thousands of Kupier Belt objects larger than Pluto.

Be true to something so Frozen, and let it go.

Why are you amazed?

These sort of taxonomical debates are exceedingly coming in biology (eg "is this a new species or just another variant?", "how many base pair differences are required to be a species?", Etc).

Taxonomy for planets and other celestial bodies is increasingly important as we discover more and more exoplanets. And it turns out that writing a good definition is hard... especially when we have so few exemplars in our own solar system.

I wasn't aware that they'd discovered any Kuiper Belt Objects (KBO) bigger than Pluto.

From everything I can find, Eris is more massive, but Pluto still has the bigger diameter (as confirmed by New Horizons), and everything else is quite a bit smaller.

Fake news! The most obvious give aways in the title being planet and orbits. Earth is not a planet but a plane and it doesn't orbit anything as it is stationary.

I would prefer a definition based on how round the object is. If it's round or a rotational ellipsoid close enough to a sphere, it's a planet.

Is the Moon a planet?

I was wondering before if it would count as a planet if it wasn't bound to Earth. It is around 6 times more massive than Pluto. There are also other, bigger moons in our solar system, such as Ganymede, which has about half the mass of Mercury (but also has a bigger diameter, due to being significantly less dense).

One could defend the Earth-Moon system to be a double planet. The Moon is much too large compared to other satellites in the solar system.

This is called Hydrostatic equilibrium[1] and is one of the factors at play when determining if a body is a dwarf planet/planemo.

[1] https://en.wikipedia.org/wiki/Hydrostatic_equilibrium

If Earth and Pluto were planets, clearly Gustav Holst would have written movements for them as part of his Planets suite, but he did not.

Ergo, they are not planets.

Earth is a ‘dwarf planet’ because taxonomists are better at making useless headlines than doing actual work.

What's in a name? That which we call a rose by any other name would smell as sweet.

"A blegg by any other name..."

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