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(io9)   Old and busted: Pluto isn't a planet. New hotness: Earth isn't a planet   (io9.com) divider line 75
    More: Interesting, planets, dwarf planet, Earth, dwarf galaxies, asteroid belt, gas giants, International Astronomical Union, rocky planet  
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8305 clicks; posted to Geek » on 16 Aug 2013 at 8:27 PM (1 year ago)   |  Favorite    |   share:  Share on Twitter share via Email Share on Facebook   more»



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2013-08-16 06:08:02 PM  
I'm ok with that.
 
2013-08-16 06:23:29 PM  
♫ Well, they call me debris
I keep goin' round the Sun.
Yeah, now they call me debris
I keep goin' round the Sun.
They won't let me be no planet
Won't let me have no planet fun.
 
2013-08-16 07:31:52 PM  
I was expecting Earth-Moon co-planets. The thing is humongous to Earth, as compared to the other moons.
 
2013-08-16 08:32:42 PM  
Is anything real? Or is it that by observing things we perceive them to be real?
 
2013-08-16 08:33:06 PM  
That's a pretty compelling argument.

I would add "has its own stable orbit around its star" to his definitions, but other than that its hard to quibble.
 
2013-08-16 08:33:48 PM  
didn't want to live on  this planet anymore anyways
images.wikia.com
 
2013-08-16 08:36:39 PM  
Duh, it's a mudball. Everything evil and bad about life is here. A perfect vacuum with deadly radiation filling every cubic femtometer? Ah, that's the place to be.
 
2013-08-16 08:37:11 PM  
Aw man, does this mean we're gonna have to move? I just finally got all my boxes unpacked.

/I'm not an alien
//totally not an alien
//mind if I ram my ovipositor down your throat and lay my eggs in your chest?
 
2013-08-16 08:39:22 PM  

Sim Tree: I was expecting Earth-Moon co-planets. The thing is humongous to Earth, as compared to the other moons.


Meh. The barycenter of the Earth-Moon system is still within Earth's radius, it's not a double planet.
 
2013-08-16 08:40:30 PM  
It's "affects" not "effects".  Stopped reading because anything following is invalid.
 
2013-08-16 08:44:18 PM  
I dunno, he calls the various planet definitions convoluted (and a lot of the proposed ones were), but the one that we're actually using now is almost identical to his.

According to him, a planet:

1. is in orbit around a star,
2. is not self-luminous,
3. has sufficient mass to assume hydrostatic equilibrium (a spherical or nearly spherical shape), and
4. dominates the other bodies orbiting the star

#2 isn't *explicitly* included in the current definition, but is implied because bodies that are self luminous already have a name - stars. Otherwise, if you simply replace 'orbiting the star' with 'in the area of its orbit' in #4, you've basically got the current definition. I don't see how his is any simpler in structure. 'Dominating the other bodies orbiting the star' isn't conceptually any more objective than 'dominating the other bodies in the area of its orbit' - both are subject to the same ambiguities in the presence of a smoothly varying size distribution of orbiting objects, it simply happens that in our universe the mechanics of planet formation work out such that his definition wouldn't run into the problem as often.

Given what we currently know, in my opinion there's nothing significantly wrong with our current definition. It's not absolutely perfectly clear and unambiguous in 100% of all imaginable cases, but I don't think it'd be possible to create a definition which *was*. The universe doesn't like to be put into such neat and tidy boxes.
 
2013-08-16 08:49:40 PM  
Moronic obsession with meaningless boundary conditions and categorisation is moronic
 
2013-08-16 09:03:41 PM  

EdgeRunner: Aw man, does this mean we're gonna have to move? I just finally got all my boxes unpacked.

/I'm not an alien
//totally not an alien
//mind if I ram my ovipositor down your throat and lay my eggs in your chest?


buy me a drink and lets talk ;-)
 
2013-08-16 09:05:39 PM  
Oh..... shaddup.
 
2013-08-16 09:08:33 PM  
Go home science,
dl.dropboxusercontent.com
you're drunk.
 
2013-08-16 09:22:38 PM  
Subcategories? We already have them - rocky/terrestrial, and gaseous.

This is trying to round and ignore significant decimal places.
 
2013-08-16 09:46:50 PM  
For instance, there is not an iota of confusion regarding where "gas giant" ends and everything else in the solar system begins. There is no gradual shading of gas giant into rocky planet.

I would challenge this. Perhaps we haven't found such a planet yet, because there isn't one in our solar system and we can't see exoplanets at that level of detail. But there's no reason that a rocky planet couldn't become more massive, gradually allowing it to hold onto a thicker and thicker atmosphere, until a dense layer of clouds obscured the entire surface of the planet. Voila! Gas "giant." The more massive the planet becomes, the further out from the core the gravity remains sufficient to prevent the escape of hydrogen, and the larger the apparent radius of the planet.
 
2013-08-16 09:53:36 PM  
FTFA: Judging by the planets discovered around other stars, our solar system seems to be typical in being dominated by gas giants, which appear to be ubiquitous among star systems. All of which would seem to suggest that gas giants are the rule.

Someone get zombie Malmquist to slap this guy. If you want to argue that the mechanics of star/planet formation favor groups of gas balls forming together, that's a sound argument. But "we see a bunch of them and not a lot of the smaller ones" is a very bad argument to make, especially in astronomy.

/yes, I know Malmquist bias refers to magnitude
//it still works, go away
 
2013-08-16 09:59:23 PM  
i703.photobucket.com
 
2013-08-16 10:02:01 PM  
This is why Isaac Asimov was so brilliant:  He, like all the others of his kind, was able to consider problems without being weighed down by what anyone else had said about them.  He didn't ignore the others' theories, he simply went beyond them. From Nightfall to the Foundation series, I, Robot to The Intelligent Man's Guide to Science, he was the thinking man's author.
 
2013-08-16 10:02:58 PM  
I hope not, that's where I keep all my stuff!
 
2013-08-16 10:10:48 PM  
But what of Planet Houston?
 
2013-08-16 10:15:21 PM  
"What if the definition of "planet" were instead that a body "

I see, you're full of shiat.  Ok and what if a planet was white and fluffy and liked to puke on my carpet?  We could call it Caturn.

www.catster.com

fark YOU, STOP WAKING ME UP AT 4AM, CATURN
 
2013-08-16 10:18:15 PM  
This is dumb. Our entire concept of a planet is based on the object we currently inhabit. If anything is to be reclassified it should be the gas giants.
 
2013-08-16 10:18:19 PM  
Considering that the rocky bodies in the original meaning of the word "planet" outnumber the gas giants - if they want to change the definition, call the big ones something else.  Sub-stellar objects, perhaps.
 
2013-08-16 10:18:55 PM  

FROGSTOMPER: [i703.photobucket.com image 800x525]


Beautiful!
 
2013-08-16 10:22:41 PM  
Would Earth trojan asteroids allow Earth to meet criteria #4?
 
2013-08-16 10:37:52 PM  
Headline fail. Pluto IS a planet - a dwarf planet.
 
2013-08-16 10:50:15 PM  
How could two objects as radically different in every way as Earth and Jupiter both be "planets?"

Just like a jellyfish and an elephant aren't both animals.

That article was bad and subby should feel bad.
 
2013-08-16 10:59:26 PM  

EdgeRunner: //mind if I ram my ovipositor down your throat and lay my eggs in your chest?


*flips through book* Throat?  No... don't have one of those... looks tasty though.

/Also totally not an alien.
//Have you seen the new J59 jump initiators?
 
2013-08-16 11:13:12 PM  
Welcome to earth third rock from the sun.
 
zez
2013-08-16 11:24:02 PM  
Where does this fit?

upload.wikimedia.org
 
2013-08-16 11:32:32 PM  
Yes Asimov did once describe the Solar system as that.  Pity since then we've discovered quite a few balls of rock as well.

Funny thing and you'd think io9 would of know this; the reason we haven't found any Earth sized balls of rock is... we can't actually detect them yet.  Too small, hence everything seems to be 'super Earth' sized and such.

In much the same way planets were once rare (they aren't), water was impossibly rare (it's not) and the moon was a barren lifeless rock with nothing useful on it (Helium3 seems quite useful, so 'its not') I'm sure when we've got the instrumentation we'll discover Earth sized planets aren't rare either.

/io9 Journalistic integrity my left nut.
 
2013-08-16 11:34:24 PM  

zez: Where does this fit?


Uranus
 
2013-08-16 11:36:50 PM  

theorellior: Sim Tree: I was expecting Earth-Moon co-planets. The thing is humongous to Earth, as compared to the other moons.

Meh. The barycenter of the Earth-Moon system is still within Earth's radius, it's not a double planet.


It's a little more complicated than that, because technically the moon orbits the sun, not the Earth (which would make them both planets, but not a binary-planet system). Allow me to explain:

The Earth tugs on the moon's orbit so that it wobbles as it does so, but the moon doesn't actually orbit the Earth because the barycentre is too far away from earth's centre and it's getting farther away (the moon is slowly pulling away at about 1.5 inches a year. In about 1 million years, it will be too far away to cast any more total eclipses, and in 50 million years it won't cast any eclipses at all).

What does this interstellar dance look like? Think of two different-sized racecars on an oval track, with a tether attached to them and the sun in the middle of the track. The smaller car (the moon) occasionally passes and falls behind the larger car. But they are both on the same track, and they are both going forward. An ordinary moon has its own small track around the larger car, and ignores the big one around the sun.

visual aid:

webspace.utexas.edu

From Earth's perspective, the moon orbits us. From the Sun's perspective, the moon just alternates hiding in front of us or behind us. Though we don't fit the official criteria of a double planet system, we're closer to that than an ordinary planet-moon one.

For the physics to back this up
 
2013-08-17 12:15:09 AM  

plumbicon: This is why Isaac Asimov was so brilliant:  He, like all the others of his kind, was able to consider problems without being weighed down by what anyone else had said about them.  He didn't ignore the others' theories, he simply went beyond them. From Nightfall to the Foundation series, I, Robot to The Intelligent Man's Guide to Science, he was the thinking man's author.


If only he were a good writer.
 
2013-08-17 12:22:52 AM  

Ishkur: because technically the moon orbits the sun, not the Earth


2.bp.blogspot.com

Ishkur: moon doesn't actually orbit the Earth because the barycentre is too far away from earth's centre


photos1.blogger.com

the moon does orbit the Earth.  Definitively.  It also orbits the Sun.
 
2013-08-17 12:24:33 AM  
I was saying this something like this when the Pluto fiasco was going on. Planet doesn't really mean anything. The classification should be along the lines of glass giant/rocky body/ice body. MVEM, most moons, and asteroids are rocky bodies. JSUN are gas giants. Pluto, Titan, Charon, comets, and KBOs are icy bodies. (More or less.)

Then, if you still want to define planets as an informal classification, you can use the ridiculous current definiton, or do something like define a minimum diameter, etc. But it'd be informal. Kind of like "tree" is an informal kind of plant in botany.
 
2013-08-17 12:49:31 AM  

SacriliciousBeerSwiller: This is dumb. Our entire concept of a planet is based on the object we currently inhabit. If anything is to be reclassified it should be the gas giants.


No, Planet comes from "wanderer" and referred to "stars" that did not move with the fixed stars of the constellation.  Since the Earth cannot move across the field of the fixed stars from a reference point of the Earth itself, by definition it cannot be a planet.

What they need to do is simply go to the original IU proposal that required a planet directly orbit its star and have enough mass to naturally round; bogus weasel-shiat like "substantially" and "local area" which are totally subjective measures.  But, as written, if we found a planet bigger than Jupiter out in the Kuiper Belt, it is a dwarf planet - or maybe a planetesimal, depending on what local and substantially mean to whomever is on the IAU Committee for Anal Retentive Bullshiatting
 
2013-08-17 01:02:38 AM  
Dump #4 and I will agree with the definition.  And -- oh look -- the "problem" goes away.

/PhD in Astrophysics, so, yes, my opinion is better than yours.
 
2013-08-17 01:14:18 AM  

phalamir: SacriliciousBeerSwiller: This is dumb. Our entire concept of a planet is based on the object we currently inhabit. If anything is to be reclassified it should be the gas giants.

No, Planet comes from "wanderer" and referred to "stars" that did not move with the fixed stars of the constellation.  Since the Earth cannot move across the field of the fixed stars from a reference point of the Earth itself, by definition it cannot be a planet.

What they need to do is simply go to the original IU proposal that required a planet directly orbit its star and have enough mass to naturally round; bogus weasel-shiat like "substantially" and "local area" which are totally subjective measures.  But, as written, if we found a planet bigger than Jupiter out in the Kuiper Belt, it is a dwarf planet - or maybe a planetesimal, depending on what local and substantially mean to whomever is on the IAU Committee for Anal Retentive Bullshiatting


If there was a body more massive than Jupiter sitting in the Kuiper Belt it would have long ago cleared its orbit of anything else (or completely dominate anything left), so it'd still be a planet.
 
2013-08-17 01:14:26 AM  
I'm pretty sure High Zogaxyan-B has different words to describe solid bodies that dominate their own orbits, gassy bodies that can have solid bodies in orbit around themselves while not  being stars, and your mother.
 
2013-08-17 01:33:46 AM  

Ishkur: It's a little more complicated than that, because technically the moon orbits the sun, not the Earth (which would make them both planets, but not a binary-planet system). Allow me to explain:


Short answer:

Nope.  The general rule is that if a moon is closer than the L1 point (the point where the Sun's gravity and the planet's gravity are equal), then it's considered to be orbiting the planet.  If it's further from the planet than the L1 point, it orbits the Sun.  The Earth's L1 point is about a million km away; the Moon orbits about 300 thousand km.  Therefore the Moon orbits the Earth.

Long answer:

Technically, orbits don't exist at all, except in a Newtonian system where there are exist only two massive particles and no other forces besides gravity.

A system with more than three particles (aka "bodies") is chatoic and "orbits" aren't stable.  Technically.  In practice, things like relativistic effects, tidal forces, and drag tend to damp out the chaotic motions,, so things that are like orbits do tend to form.  But just because they are like orbits, it doesn't mean that all bodies aren't interacting to some extent.  Arguing over whether the Moon orbits the Earth or the Sun is a bit silly since they are all affecting each other.

Nevertheless, scientists and engineers who analyse orbital motion tend to do their calculations in terms of ideal orbits (because the equations are simple), and, when three bodies are present, to define "boundaries" where particular bodies dominate the local gravitational field.  What is this boundary?  It's a sphere with a radius equal to the distance to the L1 point.

What does that mean?  If a scientist is analysing the motion of a body that is closer than 1 million km to Earth, they will consider the body to be orbiting Earth and use equations for Earth-orbit.  If the body is further away, they will use equations for solar orbit to analyse its motion.  (Note: it's a little more complex than that, but that is basically how they do it.)

Because the Moon is much closer to the Earth than the L1 point, a scientist analysing the Moon's motion will use equations for Earth-orbit.  Therefore, according to a scientist or engineer, the Moon orbits the Earth and not the Sun.

/majored in Aerospace Engineering
 
2013-08-17 01:44:52 AM  

The All-Powerful Atheismo:
[2.bp.blogspot.com image 200x147]


You posted images from a dumb game show.

I posted physics. I still win.
 
2013-08-17 02:12:24 AM  

Ishkur: The All-Powerful Atheismo:
[2.bp.blogspot.com image 200x147]

You posted images from a dumb game show.

I posted physics. I still win.


No, you still lose and because you're implying that Earth and Moon have equivalent movements when they don't. Moon cycles and Solar years don't align. And it takes 19 years for them to go back to the initial relation, which is not only a rather large differential but also a prime number, which makes it even harder for your theory.

Also, you can't read/understand sinusoidal representations of circular movements.

www.kowoma.de

"OMG, that sattelite is totally not orbiting earth, it's not a circle, see?"
 
2013-08-17 02:14:24 AM  

Ishkur: The All-Powerful Atheismo:
[2.bp.blogspot.com image 200x147]

You posted images from a dumb game show.

I posted physics. I still win.


yes you win.  you win the shiat physics award.

/and you didn't post physics, you posted a link to a page that contains barely some physics, and doesn't say what you said let alone prove it.
 
2013-08-17 02:15:12 AM  
If the sun suddenly disappeared, what would happen to the moon?  would it go off in its own direction, or would it continue rotating around the Earth?
 
2013-08-17 02:20:42 AM  
In other words:
My arbitrary definition of a planet is better than yours because it is "controversial" and will get me page views

This is really stupid. Any definition is arbitrary and theirs is certainly no less so than the IAU definition. Besides, there are already subclasses of planets. One of which is used repeatedly in the article, "gas giants" to cover the difference. And size isn't the determining factor for many things. The difference between the largest and smallest stars, both in terms of mass (about 1000 times) and diameter (about 22.5 million times), is far greater than that between Jupiter and Earth (318 and 11 times). We don't say that any smaller stars are not stars, but classify them as different types of stars.

Complain all you want about the IAU definition, but the article is pretty stupid.
 
2013-08-17 02:24:14 AM  

Vaneshi: EdgeRunner: //mind if I ram my ovipositor down your throat and lay my eggs in your chest?

*flips through book* Throat?  No... don't have one of those... looks tasty though.

/Also totally not an alien.
//Have you seen the new J59 jump initiators?


Ooo, the J59s are the swooziest saucer upgrades since the Kagrin gravity nullifiers..... is uhhh... JUST what I'd say if I was an alien! Which I'm definitely not! Now if you'll excuse me, I'm off to Google some of your fine selection of Tyra Banks and Christina Ricci digital pictographics. I do so appreciate those women with the big, round, beautiful foreheads!

I joke of course. I was in fact expressing a perfectly normal prurient interest in their mammary glands. I'm clearly not a big foreheaded alien homesick for his own kind. Why, even if I did have a big forehead, it would be securely hidden beneath my luxuriant bouffant hairdo, which I'm assured is all the rage among Earthmen of my chosen age and nationality, so there is no reason to suspect me of being an alien. Honestly, I can't understand why you Earth people keep making these wild accusations.
 
2013-08-17 02:55:02 AM  
Who the hell is this guy and what wankery is this?

The status of a planet is about mass and the gravitational force that mass asserts. All planets are rocks, 'gas giant' is only a reference to describe whether or not the planet has trapped a rather large quantity of gas by the rock.

He'll sure feel like an idiot in a thousand years when we're banging these rocks together to make planets of larger mass, hoping to ignite a new star.
 
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