No, there is no flaw in this, and moreover there is nothing new in this. This is how it has always been, it is not something invented recently.
In the Solar System, there are 3 Mercury-sized satellites and other 3 Moon-sized satellites, besides the Moon. If they had not been in their orbits as satellites, they might have very well been planets. Therefore the old definition of "planet" also depended on the orbit of the body, not only on the size and shape of the body.
Most of those satellites are bigger than Pluto. Triton, the biggest satellite of Neptune, had been in the distant past another planet with an orbit close to Pluto, but it was captured by Neptune and it has become a satellite. Otherwise it would have remained a "dwarf planet", orbiting close to Pluto. So Triton was demoted from "planet" to "satellite", by Nature, not by a human organization.
The current definition of "planets" and "dwarf planets" is fine.
If anything, there are too few planet classes, not too many. A more useful classification is into big planets, medium planets and small or dwarf planets, where the Solar system has 4 big planets, 4 medium planets, and a lot of small planets.
The big planets, i.e. which are big enough to retain the volatile chemical elements, like hydrogen and noble gases, not only the refractory elements, have a very different chemical composition from the medium planets, and this difference will also exist in any other stellar system that has condensed from gases like those at the origin of the Solar System, with more oxygen than carbon (there exists the possibility of stellar systems with a different chemical composition than the Solar System, formed by condensing from gas mixtures with more carbon than oxygen).
It’s serviceable, but is it ideal?
What’s the scientific advantage in categorising “planets” and “dwarf planets” as two separate categories, compared to unifying them into a single category (possibly while retaining the distinction as two different subtypes of “planet”)?
Which system would be more scientifically useful? Which would be more parsimonious?
- a gang of dwarfs
- some rocky ones
- and gas giants
- and one star to rule them all
As I understand it, in fact, there was discussion about defining systems like Earth-Moon as double planets, but that didn't make it into the final definition.
Huh?
You would think this group of well educated, critically thinking adults would go "sure", but something fundamental in their brains just refuses to let them accept this meaningless change to their lives.
Now scale this up to actual impactful topics like religion, politics, relationships, race and more and most conflicts around the world start to make sense.
(I say this as someone who doesn't care either way whether Pluto is a planet or not.)
1. Yes, there are culturally significant things that have happened since the 1930s, including the discovery of Pluto and its designation as being a planet. In fact, in 2006 -- far more recently -- a group of people got together -- known as the IAU -- and they also performed a cultural act amongst themselves when they decided to stop calling Pluto a planet, undertaking a social process ("voting") in adopting criteria for doing so.
2. If you would rather define a planet as a wandering star that's visible to unaided humans in the night sky, I'd respect that, and I kind of like the idea. It's somewhat romantic, and it avoids the myriad issues that the article here discusses that have caused the 2006 IAU definition to start to smell bad. However, it's really none of my business. The problem comes up when you police what other people call things, not when you decide to subscribe to the IAU of your own volition.
Historically and culturally, Pluto is considered a planet. An IAU classification shouldn't be used to try and retroactively change that, because the IAU does not have control over history and culture. It's a fun fact (did you know that Pluto is not classified as a planet by astronomers?) not a diktat.
Similarly, a banana is 'officially' a berry, which means that it is classified as a berry by botanists. This does not mean it is considered a berry in any other contexts. If you told someone you had made a berry crumble and it was filled with bananas, you would look strange. We have countless examples of this (often focused around food): a tomato does not belong in a fruit salad no matter what botanists say.
Different terms are used with different specificity in different settings. Language and culture and [older disciplines] are not governed by the rules of [newer disciplines or bodies]. If people with 'I love space' t-shirts would stop "um actually"-ing, no one would have a problem.
A very brief period of history. Give it 50 years and the number of people who will call it a planet will be close to 0.
Let's not overstate Pluto's significance in culture. People call it a planet only because that's what they were taught in school. Not because of other (very few) cultural references. As it has been dropped from the curriculum, so shall it be dropped from people's minds.
Compared to the other planets it's rarely referred to in stories, etc. It has very little significance in today's culture beyond the fact that it was taught in school.
That's not the case for something like Jupiter. If they decided tomorrow that gas giants are no longer planets, it will remain in arts and culture. Pluto? Highly unlikely.
I don't think my kid knows about Pluto. That doesn't bother me in the slightest.
Botanical berries: Bananas, tomatoes, grapes, cucumbers, eggplants, avocados and peppers, but NOT strawberries, raspberries, blackberries or mulberries.
Scientists really should have made up their own categories instead of using our words.
If they could do it all over again probably most of them would. The sciences all grew organically too. Some of these things like "berries" aren't even just the product of one reclassification, they're the product of several over the course of decades or centuries, which is how they get so common-sense silly over time.
Doesn't really matter. The public would end up taking science words for their own purposes to sound legitimate. Look at how "quantum" and "energy" is used in alternative medicine.
The word “planet” signifying a certain reverence, and the fact that a scientific body was now policing everyday language — for the apparently petty reason that we should not honor Pluto as we once did — it was quite a misstep for how people in the public might view science going forward. Unless, perhaps, the idea was to make people more skeptical of scientific results and statements.
That would also have had an impact on the public view of science. Perhaps not as bad, but it would have had an impact.
If you believe in the "standard 9" you're just insisting on returning to a scientific definition of planets but one that is frozen on our scientific understanding from a few decades ago...
If we're segmenting off "modern astronomy" then Pluto wasn't even discovered yet.
And we discovered Ceres long before Pluto. It would be pretty rude to keep excluding Ceres just because we knew about the asteroid belt before we knew about the Kuiper belt.
I’m not a member of the IAU. I don’t adhere to their linguistic prescriptivism, and nobody should expect that I will. Some of their own members do not — the article here explains.
Are you a member of the IAU?
I’m not the IAU, and I have no interest whatsoever in emboldening thousands of people to smugly harass you or anybody else about it.
I’d encourage you to think about the impact of science fiction on interest in science. Culture is an extremely powerful force. I don’t think your concern would bear out.
As the article here explains, the 2006 IAU definition doesn’t really make sense or function as a useful model for what a planet is.
This is the actual problem everywhere.
Conclusively, science class would not teach Pluto as a planet (it should after all stick to the science) and English class will discuss the cultural impact of planet Pluto! Maybe write poems about the importance and impact of 9 word mnemonics? Sounds fun.
My headcanon is that people would hate it so so much! I can't wait to see that as a distant observer.
People need to understand the dynamic between science and society, because that is an important part of how the world works today.
Pluto is an exemplar.
And also, the value of culture. It might not be a scientific result, but it still shapes our experience of the world. Pluto is beloved.
It honestly doesn't have to be a bunch of drama. The problem will pretty much go away after the current generation who grew up learning about Pluto as a planet dies off and gets replaced by a generation who always knew that there were only 8 planets in our solar system. Hopefully they'll also be better prepared to accept changes that come from better understanding.
What would you say to scientists and laypersons who consider Pluto to be a planet? How would you persuade them to your own viewpoint? Please give at least three examples and use at least three paragraphs.
Some people remember being told that it was a planet when they were kids and they cling to that even though we've learned that it doesn't make sense to call it a planet anymore.
Apart from that it shows up as a planet in literature, almost all of which was written before we knew better, just like how the idea of earth being at the center of the universe shows up in literature and was once a part of our culture. The geocentric model had passionate holdouts too, but we've mostly moved on from that idea since and I think we're better off for it.
For scientists and laypersons who aren't just holding onto "planet" for sentimental reasons, I'd recommend the book "How I Killed Pluto and Why It Had It Coming"
The word “planet” is neither true nor false. Different people use it to refer to different things.
Kind of like the word “tree.” Some things are trees and some things are not — and it really depends on whom you ask and when you ask them. Most people are able to get along and allow people to refer to whatever trees they want to, because it’s a free country and it really doesn’t make sense to try to control other people over something like that.
But that’s not what happened here. The definition was changed. We didn’t learn anything new about Pluto that made us say “ah, we thought Pluto had a solid core but apparently it doesn’t, so it’s not a planet”. All the relevant facts about Pluto remained the same. The reason why it’s no longer considered a planet is because of the term ‘planet’, not because of Pluto.
I disagree. Quibbling about a definition like that is like quibbling about whether a certain bird is a black-crowned Night-Heron or a black-crowned Night Heron (without the second hyphen), which is a real controversy that took place.
I suppose it shows a socially constructed, human aspect of science, but it really has very little to do with actually understanding the universe. The universe doesn’t care about our arbitrary stamp-collection-style classification of objects. There’s no equation or physical theory that describes the difference in any meaningful way.
The universe doesn’t care about our arbitrary stamp-collection-style classification of objects, anymore than it cares about where elements sit on the periodic table, but for us humans having things classified and ordered is a big deal. It's our constant arbitrary naming and organizing and classifying that allows letters to get delivered to my house and packets to reach my network. It gives us more precise language and enables better focus on what matters. It helps build a foundation for teaching and research. It helps to catalogue all we've learned. While you'll find plenty of ego fueled petty squabbles around the naming and classifying of things, it's still a pretty big part of what science does and we'd struggle to teach or coordinate any sort of meaningful science without it.
It gets worse. Whales and dolphins are more closely related to certain fish than those fish are related to some other fish. (As are we by the way.) There are also some fish, such as lungfish or certain eels which can spend more time out of water than whales and dolphins can. Some fish can even breathe air, which undermines another assumption about whales etc.
For some reason, I rarely hear fewer people objecting to jellyfish or shellfish being referred to as fish, even though these are more distantly related to fish than mammals are.
So biologically, the term "fish" doesn't make much sense.
There’s no need for a god complex. Stop picking and choosing which planets are real. Scientists can create their own, more precise words for things. Planets are sacred. Things that clear their orbits are not.
You can’t subdue the public into giving up their gods out of difference to science — you’re just losing people.
So… planet Ganymede when? Or Titan?
That's an objection? No, that's a benefit! I think it'd be awesome to be regularly discovering new planets.
We can still be reasonably excited about discovering new things in the solar system without pretending they're in the same category as Earth and Neptune.
Have whatever emotional relationship you like with "Pluto" and don't wait around for others to validate it. It's fine. Nobody can stop you. I'm a bit fond of Ceres myself. Nobody can stop me. Nobody needs to approve it. Take control. Write your own headcanon.
- Orbits a star (Pluto does and I assume that's what you were asking about)
- The object has enough mass to pull itself into a sphere (meets this criteria)
- The object has enough gravity to have cleared its nearby orbit of debris and other objects
Neither Pluto nor Eris qualify for a planet because of that last one and, like I mentioned, the Moon has more mass than Pluto and Eris. The Kuiper belt objects all have this issue, but my point was that dwarf planets are pretty small - especially compared to other objects around Sol. If you walked non-stop around the Moon it would take 91 days compared to Pluto's 62 days and Eris's 61 days.
The designation of dwarf planet is not that big of a deal imo.
People like to make rules. Leave them be in their tree houses, unless you really like to play too. I thought it was a right of passage in high school to laugh at the French forming committees to tell peasants how to speak their native language. We haven't generalized from this example?
Who gives a rat's ass whether this governing body thinks Pluto is a planet or not?
Flat-earthers are definitely wrong about the shape of the earth, but even they admit the sky is blue, assuming they aren't afflicted with some unfortunate variety of colorblindness.
In my observations of flat-earthers, they're people who reject the consensus surrounding a particular fact because they haven't observed that fact for themselves, which doesn't make them bad people or even crazy. I do rather enjoy their attempts to measure basic scientific facts about the earth, such as when a group of flat-earthers used lasers and the ocean to measure if the earth indeed has curvature. When the evidence incontrovertibly showed the earth indeed has sufficient curvature to match the scientific consensus, many participants were quite shocked. As long as they adjusted to the consensus, or even hypothesized another theory they felt worth testing, they're not crazy, just skeptical of authority.
I have not observed directly that a human will die after 3 days without water but having experienced thirst & dehydration in limited amounts, I have no reason to doubt that is likely the case.
That's what I don't understand supposed "rational" flat earthers. It's fine and somewhat rational to be skeptical of authority but when the contrary idea takes enormous leaps of faith to consider, it seems weird to me to believe something for the sake of it.
I know someone who is almost 40 years old that has never left his hometown. He's a reasonable person who holds gainful employment, but from our conversations, he's never been in a skyscraper, flown on an airplane, taken a road trip into the mountains, or even hiked up a large hill, for that matter. He also lives in a land-locked city, so he's never seen the ocean. As such, he has never directly observed the earth to be curved. With all due respect, many people like him do exist in the world, and perhaps you're not acquainted with people like him.
However, he is not a flat-earther because he spends much time on the Internet reading about the way the world works outside his hometown. Basically, he believes in the truthfulness of large institutions, which really is why you and I believe the earth is round; that is, we haven't actually performed a bona fide experiment (not just going in an airplane or up a mountain) to measure the curvature of the earth for ourselves, but we trust the results of those who have, and we also accept that certain technologies like GPS as it is currently implemented can only work if the earth is round (not just in satellite orbits but also the slight-but-critical relativistic shift from a geosynchronous satellite).
>when the contrary idea takes enormous leaps of faith to consider, it seems weird to me to believe something for the sake of it.
That's cool, but many people are capable of believing in something for the sake of it. One fact that stands out to me is that we all use some amount of faith to accept that the earth is round, though perhaps not quite a leap's worth.
I haven't, and you probably haven't, though if you have, I'd love to hear that story. As I said, they're skeptical of authority and need to run the experiment themselves; some will even flip on flat-earthers who run the experiment and change their minds. Only those who perform the experiment and still refuse to accept the outcome are deserving of being left to their own crazed devices. Until then, they're just ignorant and/or weird.
I believe someone was trying to make a name for themselves here and ignoring the history of Pluto and its discovery.
Why bother coming up with a pseudo-scientific requirements list for planets when these don't work for a large number of cases.
There is because Pluto is inside the Kuiper Belt and just as much a part of it as all the other "planets" in there. There's nothing wrong with defining our solar system as having 8 planets plus a bunch of other stuff.
It's really hard to come up with a definition of a planet that includes Pluto but doesn't include Orcus. Orcus is very close to a mirror of Pluto that is 120 degrees out of phase. Even in name: Orcus is the Roman name for the Greek god Pluto.
If you want to say that Pluto is a planet for historical reasons, that's fine. Just don't try to invent pseudo-scientific nonsense to justify it at the same time you are decrying psuedo-scientific nonsense.
A Kuiper Belt Object not being a part of Solar System doesn't make any sense. A star system is the star + all objects that orbit it. Why would you arbitrarily exclude some objects that orbit the Sun?
Eris is bigger than Pluto, so if Pluto’s a planet then so is Eris. So you have 10 planets.
And then how many other Erises are still hiding? How many planets do we have then? It must be some very large unknown number!
Holding the true number of planets to be a large unknown number was anathema to many.
The demotion of Pluto was primarily motivated by a desire for the word “planet” to refer to a fixed, never-changing number of large bodies orbiting the sun.
Which is exactly how I remember learning it at the end of highschool (discovered during my junior year): Hey, did you know we just discovered a tenth planet?
How is it pseudo-scientific?
This is like when English professors gripe about word usage in books. That's wrong, you can't do that. Then society at large does it and it becomes correct usage. We define our world.
As human beings we're allowed to make these kind of decisions. We define ourselves to be outside of the animal kingdom when we're clearly part of it and a type of animal ourselves.
The question at hand is "how do we define a planet" from a universal standpoint, because it hadn't really been defined beyond an "I know it when I see it" level and that was becoming a problem.
Objective rules that do not assume you're talking about our solar system are key here, and the serious proposals basically come down to 8 planets or dozens and growing, and from a practical standpoint the former was the obvious choice IMO since all it really affects is what gets focused on in general education environments.
If you just want to make an arbitrary decision that these things are planets because you want them to be as opposed to because they meet certain criteria, that's not useful to anyone.
Pluto is the Princeps of Kuiper Belt Objects, the First Among Equals. It is the most honored KBO, even if it is not a planet.
100%
Scientists try to coin new terms all the time. It’s great for the researcher if people actually use it. But why do that when you can just sign your name on a term everyone already uses?
Redefining “planet,” from the 9 culturally accepted symbols into something else, was a swindle. “Things that clear their orbits” could have been TTCTOs. It happens all the time, coining precise terms for things. Why should this one have been any different? The public was right to push back and to protect their mythology.
In terms of financial motives, I would reason that a motive for extending the term “planet” to cover the innumerable large objects orbiting other stars would have been as a better sales pitch to Congress. Studying “planets” lightyears away was a sort of brand hack which would have driven more funding. And when the “planets” was established as comprising a virtually infinite set, rather than simply a list of 9 known objects, the nomenclature collapsed in its usefulness, which is why the IAU started looking for a way out of its own hole.
However, as the article here discusses, the IAU’s approach has pretty much failed. It doesn’t hold up to scrutiny as a thing that’s meant to be usefully applied. How exactly do you confirm that all of those exoplanets have actually cleared their neighborhoods, or is the truth that it never actually mattered to anyone in the field?
Have any scientists or agencies written papers or reported to Congress that they discovered or studied some exoplanet — using public funds — when in fact they had no way of confirming whether its neighborhood was cleared? It sounds completely improper to me, but the reality is that it never really mattered.
Scientific institutions: be nice or don’t be surprised when the general public votes to cut your scientific research funding or won’t accept important advice from experts.
To use a different phrase from wikipedia, "orbital dominance".
Other objects that stick around are either captured as satellites or forced into resonant orbits.
> The Sun attracts the Moon more strongly that Earth does, so does that mean that the Earth doesn't fit the criteria?
The Earth's sphere of influence goes out to about a million km, 2.5x the moon's orbit.
Most recent example I found was the Swatch MoonSwatch Collection [1], which includes the Sun, Moon, eight planets and Pluto[2].
1. https://www.swatch.com/en-us/bioceramic-moonswatch-collectio...
2. https://www.swatch.com/en-us/mission-to-pluto-so33m101/SO33M...
Classifying Pluto as a planet is problematic because it lacks the behaviour and characteristics of something that formed according to theories of how planets form. If you tried to describe what a planet should look like based on the nebula hypothesis, you would not be describing Pluto.
Instead it has behaviour and characteristics a lot like the many trans-Neptunian objects, so it makes more sense to classify it that way.
Also, if you have the opportunity too see @plutokiller teach planetary science or give a lecture, I can recommend you do so!
My Very Easy Method Just Speeds Up Naming Planets
And it was so convenient! Does anyone know a good alternate now that the P is gone?
My Very Easy Method Just Speeds Up Naming
- not a star
- not orbiting a planet
- roundish
- greater than 1000km radius
That would restore Pluto to its rightful place and add Eris.
Because honestly anybody who played stuff like KSP RSS or any space game taking place in our solar system represented at scale with adequat orbit weirdness probably told themselves "that's Pluto? Ok i get it, not a planet".
In celestial mechanics, "clearing the neighbourhood" (or dynamical dominance)
around a celestial body's orbit describes the body becoming gravitationally
dominant such that there are no other bodies of comparable size other than
its natural satellites or those otherwise under its gravitational influence.[0]
It’s like saying Jupiter is not a planet because the Trojans exist.
If you have to argue that it doesn't apply to Jupiter or Earth because they are obviously planets, it implies that "clearing the neighbourhood" is a vague and not particularly useful criteria.
Jupiter, Neptune and earth in your example dominate the gravity of their orbit by locking the smaller bodies into orbital reasonances.
It’s not a vague criterium. It might be an irrelevant one if you are interested in geophysics, but it’s concrete and testable.
In addition to what other commenters said about orbital resonance: Neptune has approximately 20 times bigger radius and is about 10_000 (ten thousand) times heavier. This is comparable to difference in mass between a human and a hummingbird. Could we really call them "comparable size"? I'm not sure, this is not a particularly precise term, but I would say - no.
Anyway, 9 is not an option, you must choose 8 or 10+.
Next time you go to the grocery, grab a cucumber and a watermelon and try to find the differences.
What logical rule would you propose that allows Pluto to be a planet without also bringing in a bunch of others?
If you just want to arbitrarily declare things are they way you like them to be, religion is over there.
The rule would be: pluto is a planet, stay mad nerds
Is it Art? It's not Art! Are bananas a vegetable or a fruit? Pluto definitely is a planet! No it's not!
Jesus, what a waste of energy.
Are we just realizing that asteroids come in all sizes? Do we really need a sharp boundary between those we call planets and those we don't call planets?
Can we consider planethood a spectrum? Like should we REALLY care if someone says there are 9 planets in the solar system, and the next person says 8?
We used to say there were 3 oceans, now there are 5. In reality, there's just one big saltwater lake. Do people fight about where one ocean ends and where the next one starts?
Let them call pluto a planet if they want, let them call pluto a kuiper object.
We shouldn't give a fuck.