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adrian_b 4 hours ago [-]
> “One of the biggest flaws with the IAU definition is that you can have the same object in two different orbits,” says Kornfeld. “In one, it’s considered a planet, and in the other, it’s not considered a planet.”
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).
pavlov 1 minutes ago [-]
There’s the Vulcan planet classification system where Earth is a Class M world, but I guess that won’t be adopted until 2154.
pdonis 4 hours ago [-]
Since the Moon's orbit is always concave towards the Sun, one could even argue that the Moon is a planet, not a satellite, it just happens to have an orbit that is closely coupled to that of another planet, Earth.
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.
nephihaha 41 minutes ago [-]
I have heard people argue that we are in fact in a kind of binary planetary system. No other planet has such a large satellite relative to its size, until you get to the likes of Pluto etc.
Dylan16807 13 minutes ago [-]
The Earth is closer but I don't think there's any good argument to say it's actually a binary system. Notably the Earth-Moon barycenter stays inside the Earth, and the Sun-Jupiter barycenter doesn't stay inside the Sun. But barycenters are too easy to get outside of objects anyway.
ivan_gammel 4 hours ago [-]
I‘m seeing this classification for the first time, but it sounds very reasonable and feels like it should have been like that. Is it your idea or is there any story behind it?
andrewflnr 4 hours ago [-]
We already have the terms "rocky planet" and "gas giant" that pretty much cover it. The only thing missing is an official IAU decision which, well, would have even less effect than the Pluto thing I'm guessing, since it would just be introducing a sub-division in the category.
ivan_gammel 4 hours ago [-]
Oh, right. It does exist, it is very accurate, but the names sound like LOTR party:
- a gang of dwarfs
- some rocky ones
- and gas giants
- and one star to rule them all
adrian_b 4 hours ago [-]
Many people use it, but it is not something codified formally by an international organization, like in the IAU definitions of "planet" and "dwarf planet".
lloda 3 hours ago [-]
Pluto was only discovered in the 1930s. The only cultural heritage of Pluto as a ‘planet’ is a few decades of science schoolbooks, but going by these comments you'd think it's been in the same list as Jupiter since the Babylonians.
nephihaha 40 minutes ago [-]
Uranus and Neptune don't have a long human heritage either. Neither appears to have been known to the Babylonians.
Planktonne 4 hours ago [-]
The actual problem here is weirdly aggressive nerds who are incapable of nuance, and insist that an astronomical classification (Pluto is not a planet by the IAU definition) should be used in non-astronomical contexts.
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.
concinds 1 hours ago [-]
Which would make the article's subjects "weirdly aggressive nerds who are incapable of nuance, and insist that" a non-astronomical definition be used in an astronomical context.
zdragnar 4 hours ago [-]
Peanuts, cashews, almonds, walnuts, pecans, Brazil nuts and pistachios are culinary nuts but NOT botanical nuts.
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.
jerf 3 hours ago [-]
"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.
Gooblebrai 1 hours ago [-]
> Scientists really should have made up their own categories instead of using our words.
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.
odyssey7 3 hours ago [-]
Well, the thing is, nobody got told, out of nowhere, that the “honorable strawberries” were now called simply “mildly honored straw,” because a committee of so-called experts had expressed their will, and that now everybody had to say “mildly honored straw” instead of “honorable strawberries,” or else they would be *incorrect*, because the science league said so.
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.
bryanlarsen 3 hours ago [-]
The alternative was to announce "we now have 10 more planets, and there are probably a bunch more, and we'll probably never really get a definitive number".
That would also have had an impact on the public view of science. Perhaps not as bad, but it would have had an impact.
zdragnar 3 hours ago [-]
No, the alternative would be to make up some latin sounding words for planets, dwarf planets, etc. and leave the vulgar planet alone to the standard 9 that we all know are planets.
ummonk 3 minutes ago [-]
No that would be an argument to return to the original definition of planets (highly visible celestial objects that migrate across the sky, i.e. the Sun, Moon, Mercury, Venus, Mars, Jupiter, and Saturn).
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...
odyssey7 3 hours ago [-]
This is what should have happened. (And it’s not too late — Pluto will remain with us for a while yet.)
odyssey7 3 hours ago [-]
Planets predate modern astronomy. You have to negotiate with the public if you want to change what “planet” means. To most people, in most contexts, it means 8 or 9 specific things that they have specific ideas about, not a theoretical category of infinite objects.
Dylan16807 1 hours ago [-]
> Planets predate modern astronomy.
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.
odyssey7 54 minutes ago [-]
It’s not about being rude to Pluto so much as about being rude to me.
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?
Dylan16807 51 minutes ago [-]
I didn't say anything about rudeness to Pluto, I was talking about Ceres. I like Ceres. I think it deserves some recognition for being known before even Neptune.
odyssey7 44 minutes ago [-]
By all means, call it what you like and honor it however you like.
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.
bryanlarsen 2 hours ago [-]
Few things sound more like more science than "planets". Telling people "Well actually 'planet' isn't a scientific term, it's a historical / cultural term" will also significantly reduce their trust and interest in science.
odyssey7 1 hours ago [-]
Hey, don’t blame me, blame the IAU for opening that can of worms. I’m just happy calling Pluto a “planet” and would rather the IAU had left me in peace — they’re the ones who want to argue with me about what words I’m supposed to say and when I’m supposed to say them.
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.
bob1029 2 hours ago [-]
> The actual problem here is weirdly aggressive nerds who are incapable of nuance
This is the actual problem everywhere.
nephihaha 15 minutes ago [-]
The term "fish" is a case in point. Traditionally, the term means a creature which lives underwater, which would include whales and dolphins, and indeed used to, despite being mammals.
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.
ketzu 4 hours ago [-]
I wonder how happy each group would be by this solution. Planet as a scientific and non-scientific usage.
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.
odyssey7 4 hours ago [-]
This would be a really good discussion topic in schools.
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.
autoexec 1 hours ago [-]
Pluto makes for a great lesson about science itself. Our view of the universe we live in changes over time as we get more information about it. Children should learn to expect that and to understand that it isn't a bad thing, or a flaw with science, but a vital part of the process and when it happens things are working as intended. That means that today Pluto isn't a planet, even though for a small time it used to be considered one, because we learned more about the bodies in our solar system and it no longer made sense to call Pluto a planet. We can explain to children why it shows up in our history, and how we've moved on.
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.
odyssey7 1 hours ago [-]
I appreciate your contribution to the discussion. I’d have to point out that Pluto both is and is not a planet, depending on the context — it depends on whom you ask and the situation in which you ask.
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.
autoexec 1 hours ago [-]
Pluto is a dwarf planet. It feels like less of a "is and is not" situation, and more of an "isn't, but was once thought to be" situation.
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"
ludicrousdispla 3 hours ago [-]
While reading your comment it occurred to me that virtually all reporting on (or talking about) science involves applying it to an unsuitable context. Schrödinger's cat is probably the most prolific example of this.
odyssey7 4 hours ago [-]
You’ve explained something very well that I hope certain groups of people will try to internalize.
j45 3 hours ago [-]
My understanding was part of the definition was changed thereby recategorizing Pluto?
Shuddown 1 hours ago [-]
Could someone explain what the IAU means by "clearing its orbit". For example, could we consider the Earth having not "cleared its orbit" because of the Moon? The Sun attracts the Moon more strongly that Earth does, so does that mean that the Earth doesn't fit the criteria? Or does the IAU have some sort exception for moons which they've defined some place else? I'd really appreciate if someone with more knowledge could explain.
Dylan16807 40 minutes ago [-]
> Could someone explain what the IAU means by "clearing its orbit".
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.
5555624 2 hours ago [-]
As fare as I'm concerned, Pluto is a planet. I've got a hand-written note from Clyde Tombaugh that says so. Back in the mid-1990s, a year or two before he died, I write him asking about some astronomers who were starting to question it.
drxzcl 5 hours ago [-]
> “One of the biggest flaws with the IAU definition is that you can have the same object in two different orbits,” says Kornfeld. “In one, it’s considered a planet, and in the other, it’s not considered a planet.”
So… planet Ganymede when? Or Titan?
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hn_submit 5 hours ago [-]
I'm in the same camp. I believe the classification of Pluto as a dwarf planet was arbitrary and inconsistent. I mean, it's been known as a planet for almost 80 years and suddenly we demote it?
I believe someone was trying to make a name for themselves here and ignoring the history of Pluto and its discovery.
Avshalom 4 hours ago [-]
I'm on team Pluto here but no, the problem was that Mike Brown found like a dozen 'planets' and no one wanted to deal with that. It was closer to preventing someone from making a name for themselves.
hn_submit 4 hours ago [-]
We could simply define Pluto as the edge of our Solar System and everything beyond its orbit a Kuiper Belt Object. There's nothing wrong with that.
Why bother coming up with a pseudo-scientific requirements list for planets when these don't work for a large number of cases.
autoexec 1 hours ago [-]
> We could simply define Pluto as the edge of our Solar System and everything beyond its orbit a Kuiper Belt Object. There's nothing wrong with that.
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 has having 8 planets plus a bunch of other stuff.
bryanlarsen 4 hours ago [-]
That would include Ceres, Quaoar and Orcus as planets.
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.
hn_submit 4 hours ago [-]
What part of "we define it so" did you not understand?!
bryanlarsen 3 hours ago [-]
The three I listed are inside Pluto's orbit. Part of the time for the latter 2.
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.
vova_hn2 4 hours ago [-]
> We could simply define Pluto as the edge of our Solar System and everything beyond its orbit a Kuiper Belt Object.
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?
cobbzilla 4 hours ago [-]
It was fine and dandy until Eris came along.
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.
space_fountain 4 hours ago [-]
The issue is that when we discovered Pluto we thought it was much bigger than it turned out to be. If it was as big as they thought then sure it would be a planet. As it is it isn’t even the most massive dwarf planet
hn_submit 4 hours ago [-]
They saw a problem with the discovery of other Kuiper Belt Objects and came up with a pseudo-scientific definition to "solve" the discrepancy.
vova_hn2 4 hours ago [-]
> pseudo-scientific definition
How is it pseudo-scientific?
jerf 3 hours ago [-]
Or alternatively, how would any conceivable definition not be equally "psuedo-scientific"? There isn't going to be a bright, shining line. Our own Solar System is complicated enough and if we could see out into the cosmos with equal detail the lines would get even fuzzier. Judgment calls are inevitable.
nemomarx 4 hours ago [-]
How to keep Pluto as a planet but say larger objects than it that also orbit the sun aren't planets, is the question I guess?
elictronic 4 hours ago [-]
Literally say Pluto is a planet through the collective statements of parties involved.
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.
hn_submit 4 hours ago [-]
It's basically a question of definition: we define Pluto as a planet and the others as Kuiper Belt Objects (KBO)
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.
wolrah 4 hours ago [-]
The question would be what are the specific rules that lead to that, and how you'd apply those rules outside of our own solar system. Any rule that just calls those distant objects KBOs is specific to our own solar system which is a silly rule to be making in a world where we already knew about hundreds of exoplanets.
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.
ChrisClark 6 minutes ago [-]
But why? There is no reason to care about the classification of Pluto. Why don't you just define that you're okay with it not being a planet?
tanseydavid 4 hours ago [-]
My Very Educated Mother Just Served Us Nine...uhhhm... !?
chuckadams 4 hours ago [-]
Mary's Violet Eyes Make John Stay Up Nights.
still works, how bout that?
andrewflnr 4 hours ago [-]
Nachos. She served us nachos.
odyssey7 4 hours ago [-]
> someone was trying to make a name for themselves
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.
wat10000 2 hours ago [-]
A swindle, really? Who got cheated out of money?
jerf 4 hours ago [-]
You know, this is really just a fantastic opportunity to realize the phenomenal psychological power of "headcanon". Who cares if Pluto is or is not tagged with the word "planet" by some organization you know effectively nothing about, have no control over, has no control over you, and couldn't so much as move a pebble on the planetary body in question any time in the next 20 years, if not more?
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.
autoexec 1 hours ago [-]
I agree, call whatever you like whatever you want. Just don't expect schools to teach that to anyone else. We get enough of that from the folks who want to replace science class with "God did it".
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jsbisviewtiful 4 hours ago [-]
In case anyone was curious, the Moon is bigger than Pluto. Pluto's 2/3 the size of the Moon. If any dwarf planet should be upgraded to a planet, it's Eris. Eris's diameter is over 600km bigger than Pluto's.
tmathmeyer 55 minutes ago [-]
Pluto's diameter is 2376.6±1.6 km, while Eris' diameter is 2326±12 km. Perhaps you're thinking of mass instead of size?
lenerdenator 4 hours ago [-]
Aye, but what does Pluto orbit, and what does the Moon orbit?
jsbisviewtiful 2 hours ago [-]
In order to be defined as a planet, an object needs to meet 3 criteria:
- 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.
vova_hn2 4 hours ago [-]
Pluto orbits center of combined masses of itself and Charon, which does not lie within either of them. Also, they are both tidally locked to each other, just like Moon is tidally locked to Earth.
bryanlarsen 4 hours ago [-]
The main objection to calling Pluto a planet appears to be that if Pluto is a planet then up to about 200 other objects should also be called planets, that the list would be of unknown size and regularly changing.
That's an objection? No, that's a benefit! I think it'd be awesome to be regularly discovering new planets.
andrewflnr 4 hours ago [-]
"Discovering new planets" only has the cachet it does because there are so few of them, and they are individually so significant. It would quickly lose that significance if there were hundreds of them. To be precise, it would acquire exactly the significance it actually deserves, but having diluted the meaning of "planet" as applied to the big eight in the process. We would soon want another name for the originals to compensate.
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.
derbOac 1 hours ago [-]
That's sort of what bothered me the most at the time. It seemed like the argument was that it was "emotional" or something to keep Pluto a planet when there might be so many of them. But I never understood why it was less "emotional" to insist that a planet be a certain size or that there should be a certain number of planets.
odyssey7 4 hours ago [-]
The problem is that the word “planet” refers both to cultural symbols — mythology, gods, archetypes, and the heavens — and to objects of scientific study. Those are different domains, and one of them is cultural heritage, and the other is irritating when it tries to infringe on the first one.
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.
zzo38computer 17 minutes ago [-]
I think not quite, although many planets have the names of the gods. They called them planets due to their motion, so it is still called that. The use of the same word in different contexts can have different usages and different (but sometimes related) meanings. "Planet" is used differently in astrology than it is in science (astronomy); this isn't a contradiction (although, like any words, can sometimes result in confusion if you do not make the meaning clearly).
pfdietz 56 minutes ago [-]
The obvious solution to this issue is to destroy Pluto.(*)
Many problems can be solved by application of sufficiently powerful explosives.
(*) Or, possibly, eject it from the Solar System.
wbl 52 minutes ago [-]
SUNDIAL says hello.
Sharlin 4 hours ago [-]
This seems like the least important issue in the world to keep complaining about.
Aachen 2 hours ago [-]
Deciding the color of the bike shed is easier than making important decisions about the building it sits next to. It's a well-known phenomenon https://en.wikipedia.org/wiki/Law_of_triviality
ecliptik 4 hours ago [-]
It's dumb, but whenever I see something representing the planets, I always count them. Occasionally you come across places that still include Pluto.
Most recent example I found was the Swatch MoonSwatch Collection [1], which includes the Sun, Moon, eight planets and Pluto[2].
"How I Killed Pluto and Why It Had It Coming" - awesome title for an Astronomy book
drxzcl 5 hours ago [-]
It’s not exactly an astronomy book. It’s more a memoir of an astronomer. But it’s funny and very well written.
Also, if you have the opportunity too see @plutokiller teach planetary science or give a lecture, I can recommend you do so!
tehnoslow 4 hours ago [-]
The claim that the IAU vote was procedurally invalid is interesting
Oarch 5 hours ago [-]
Back in school I learned the acronym:
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?
petcat 5 hours ago [-]
> Does anyone know a good alternate now that the P is gone?
My Very Easy Method Just Speeds Up Naming
Aachen 2 hours ago [-]
I think of them more as by properties: Mercury hasn't even an atmosphere, it's too close to the sun; Venus is a hot earth so it sits closer than us; then comes its sister planet Earth; Mars is cool by comparison and sits further away than we do. Jupiter and Saturn are harder but sit before the ice giants Uranus and Neptune, again making logical sense. Whether Jupiter or Saturn comes first, I guess there's some memorisation, with or without some sentence about it
atmavatar 2 hours ago [-]
Back in my day, we had nine planets.
adolph 5 hours ago [-]
It seems as though Pluto's primary problem is "clearing the neighbourhood." Given Pluto's orbit travels closer and further from the sun than Neptune, does Neptune also have the neighborhood clearing problem since it has not cleared Pluto?
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]
Trans-neptunian objects, including Pluto, are in orbital resonance. They owe their stable orbits to the existence of Neptune.
It’s like saying Jupiter is not a planet because the Trojans exist.
beloch 4 hours ago [-]
...or like saying Earth is not a planet because NEA's share our orbit.
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.
drxzcl 4 hours ago [-]
Except I said nothing of the sort. I said the opposite.
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.
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andrewflnr 4 hours ago [-]
The "Criteria" section of that article clarifies the question. Neptune holds Pluto in an orbital resonance, which qualifies as Neptune gravitationally dominating its neighborhood. Perfect, 100% clearance is not expected anyway, since that's basically impossible in a real, dirty world where things move around.
vova_hn2 4 hours ago [-]
> other bodies of comparable size
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.
kazinator 4 hours ago [-]
> Pluto represents the underdog ...
I see what Schindler did there!
GrumpySciGuy 4 hours ago [-]
Let the experts decide same with any other field.
jscd 1 hours ago [-]
I truly don't get why people have so much reverence for Pluto. And, unlike something like "fruit," which has a botanical and culinary definition which serve different purposes, I really don't get why anyone would care about the non-scientific definition of planet. Maybe I'm just ignorant here: what's the cultural significance of some celestial object being considered a planet?
davidguetta 2 hours ago [-]
Pluto is a planet.
baggy_trough 4 hours ago [-]
The correct planet criteria are, IMHO:
- not a star
- not orbiting a planet
- roundish
- greater than 1000km radius
That would restore Pluto to its rightful place and add Eris.
orwin 3 hours ago [-]
Why 1000 km radius? I know that 1000k diameter might be important for cold bodies to keep their equilibrium, but what does 1000km radius give?
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".
baggy_trough 3 hours ago [-]
It's just a nice round number to use as a clear boundary.
Aachen 2 hours ago [-]
Why not just have it be rounded under its own gravity? Collapse two rules into one. If nice round systems with clear boundaries is what you're going for
animitronix 4 hours ago [-]
It's time to give it up. Nobody wants there to be 23 planets...
baggy_trough 5 hours ago [-]
Bring back Pluto!
gus_massa 5 hours ago [-]
As the article explains, if you bring back Pluto you must include Eris too, and perhaps Makemake and Haumea if you ignore is not as round as expected, and who know how many other undiscovered small object near them. (And Ceres? I like Ceres.)
Anyway, 9 is not an option, you must choose 8 or 10+.
elictronic 4 hours ago [-]
Pluto is grandfathered in through the collective Consciousness of society. Just treat it the same way as tomatoes, which are officially fruits but no child believes that crap.
gus_massa 3 hours ago [-]
My daughter heard that tomatoes are fruit in YouTube, and now she wants to reclassify pumpkins and half of the vegetable as fruits.
Next time you go to the grocery, grab a cucumber and a watermelon and try to find the differences.
flerchin 4 hours ago [-]
I'm on board with all the dwarf planets. MVEMCJSUNPHME should be easy to make a mnemonic.
snapcaster 4 hours ago [-]
no you don't. just because some nerds say it doesn't make it true. just bring back pluto and nothing else
wolrah 4 hours ago [-]
Science works on logical rules.
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.
snapcaster 4 hours ago [-]
>What logical rule would you propose that allows Pluto to be a planet without also bringing in a bunch of others?
The rule would be: pluto is a planet, stay mad nerds
drxzcl 5 hours ago [-]
It’s still there. Where it always was.
d--b 1 hours ago [-]
Humanity's need to categorize things never ceases to amaze me.
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.
metalman 4 hours ago [-]
Pluto as one of the outer Canadian planets in the Canadian solar system, which as you now know is part of the Canadian Galaxy is realy such a trifling concern back on one of the Canadian Continents that contains Canada proper the center of Universal Canada, but since there is dissent on it's status something can be done through a referendum.
go ahead,laugh, but wait till google AND wikipedia both come on board
heyitsmedotjayb 5 hours ago [-]
It's been renamed to Planet America, thank you for your attention on this matter.
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).
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.
- a gang of dwarfs
- some rocky ones
- and gas giants
- and one star to rule them all
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.
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.
This is the actual problem everywhere.
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.
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"
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.
So… planet Ganymede when? Or Titan?
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 has 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.
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.
still works, how bout that?
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.
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.
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.
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.
Many problems can be solved by application of sufficiently powerful explosives.
(*) Or, possibly, eject it from the Solar System.
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...
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
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.
I see what Schindler did there!
- 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".
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.