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Author Topic: 8, not 9 planets
theamazeeaz
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Um ouch.

So the IAU voted on the planet definitions proposed. The 12 planet definition lost and the winner was a definition. Here's one article:

http://www.space.com/scienceastronomy/060824_planet_definition.html

One of my professors was there in Prague and he said:

"Overall, I think this is a reasonable definition, but it was arrived at in a highly fractious way. It was very interesting to witness the debates about this ("debate" is far too polite a term for what actually happened - conjure up recollections of student protests at faculty meetings in the late 1960s and you get more of a flavor of what it was like)."

Sad for me: I'm working on data with him about Pluto in the fall. Now Pluto is no longer a planet. [Frown]

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rivka
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I hadn't realized Brown is at Caltech. I wonder if I've met him.
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John Van Pelt
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Hey, Karl, do I have to revise the mural? [Smile]

http://www.flickr.com/photos/verbalobe/sets/608841/
http://www.flickr.com/photos/verbalobe/34140139/
http://www.flickr.com/photos/verbalobe/26734609/in/set-608841/

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Tresopax
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Uh-oh... this could mean trouble for all the science textbook literalists out there. After all, if a thing like the number of planets could turn out to be mistaken in all those old grade school science textbooks, what reason is there to believe any of the other science we were taught from those same books? We might as well just reject it all...

Or not...

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Nighthawk
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quote:
"I'm embarassed for astornomy..."
Well, I'm embarrased for English.
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Dan_raven
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Poor Pluto--first, not God enough to reign on Olympus, then not Cartoon enough to be able to talk or wear clothes, like that other Disney dog--the Goofy one, and now, not planet enough to be a planet.
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Nighthawk
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quote:
Originally posted by Dan_raven:
Poor Pluto--first, not God enough to reign on Olympus, then not Cartoon enough to be able to talk or wear clothes, like that other Disney dog--the Goofy one, and now, not planet enough to be a planet.

quote:
Gordie: Mickey is a mouse, Donald is a duck, Pluto is a dog. What's Goofy...?
Teddy: He's a dog, he's definitely a dog...
Chris: He can't be a dog, he wears a hat and drives a car...
Vern: Yeah, that is weird. What the hell is Goofy?


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GeronL
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I guess we should redefine everything
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BlackBlade
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Well there goes the only planet found by an American.

Start the cold war up boys, we are losing the space race again!

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The Pixiest
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BOO!!!!!


Since neptune hasn't cleared it's orbit of Pluto, doesn't that mean Neptune isn't a planet either?

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Morbo
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Yay! The other definition of planet proposed had too many holes in it. Better to dismiss Pluto than expand the definition.
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Orincoro
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Oh, BTW, for some interesting Wikiality, look at the Wiki article evolving over the course of the day today. This should be good.
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ReikoDemosthenes
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I always did like Pluto. Not my favourite, albeit, but up there. *mutters about square numbers of planets and leaving well enough alone*
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Demonstrocity
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You know, this may not have been "official" until now, but Pluto hasn't been considered a planet for roughly a decade now, IIRC. At least, I think it was roughly 10 years ago that I remember reading news articles about it.

My brother was taught the 8 planet model of the solar system [edit]in public school[/edit], roughly 8-9 years ago.

[ August 24, 2006, 01:38 PM: Message edited by: Demonstrocity ]

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Orincoro
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quote:
Originally posted by The Pixiest:
BOO!!!!!


Since neptune hasn't cleared it's orbit of Pluto, doesn't that mean Neptune isn't a planet either?

Actually it did a few years ago- Pluto goes inside its orbit like every 76 years or something. :too lazy to link you the wiki article:

I have heard the theory that Pluto was originally a moon of neptune, as was Pluto's own moon. I don't know if that is still the latest theory. But there is no reason to assume that there aren't a range of trans-neptunian objects we just haven't seen yet, though they would be smaller than pluto is.

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Orincoro
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quote:
Originally posted by Demonstrocity:
You know, this may not have been "official" until now, but Pluto hasn't been considered a planet for roughly a decade now, IIRC. At least, I think it was roughly 10 years ago that I remember reading news articles about it.

My brother was taught the 8 planet model of the solar system, roughly 8-9 years ago.

Depends on who you ask, same as now. It was the French Astronomical society iirc, who reinstated Pluto as a planet like 10 years ago. I was taught the 9 planet model, but with a strong reservation about how different Pluto was.

On this note- I am currently taking a lower division astronomy course on the Solar System at my university. The prof is uninterested in the debate, except to say that the politics of the thing is the only bit that's being decided. Its an American discovered planet, and it's been part of the canon of popular science for years, but astronomers have been wise to the nature of Pluto ever since its moon was discovered. Because its moon is so big in proportion to pluto, the center of gravity for the two objects together iirc, falls outside the planets, in space. This is a situation unique to Pluto if it is a planet, but common to transplutonian objects like asteroids and comets, which sometimes interact in pairs or groups with an indistinct center of gravity. Then there is matter of pluto's origin, and that it likely formed as a moon, which is another unique situation for a planet.

My prof said that basically for him, Plutinos also factor much lower on the interest scale when studying other solar systems, because astronomy is more interested in Jovian and Terestrial planets and moons that might harbor life. No-one is really looking for or caring about extrasolar plutinos.

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John Van Pelt
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quote:
quote:
Since neptune hasn't cleared it's orbit of Pluto, doesn't that mean Neptune isn't a planet either?
Actually it did a few years ago- Pluto goes inside its orbit like every 76 years or something.
I think that was exactly Pixiest's point.
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Alcon
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About time. Pluto isn't a planet, its an icy body member of the Kupier Belt. Its basically just a large icy asteriod out there on the edge of the system. We just happened to notice it and go "OOH PLANET!" before we realized that there were a whole crapload of those things out there and none of them really qualified.
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Mathematician
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quote:
Originally posted by ReikoDemosthenes:
I always did like Pluto. Not my favourite, albeit, but up there. *mutters about square numbers of planets and leaving well enough alone*

But now there's a CUBE number of planets! I don't know about you, but I certainly think that alone justifies the change.
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kojabu
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I think the article was kind of funny, but I want to fight for the right of Pluto! Its identity has been stripped away!
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Jon Boy
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It's a frozen little lump of rock. It probably couldn't care less about its reclassification.
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Dan_raven
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You could always join "People United for Pluto Planethood."

PUPP is a grass roots organization bent on one thing--giving Pluto its due respect.

Come on. Be a PUPPy. You know you want to.

Just send $19.95/week in US Legal tender, or write a check to our banking system Community Astronomers Social Helpers--or CASH for short. Send it to my address and we'll get you your official PUPPy card, newsletter, and some fabulous offers for penny stocks, viagra-like pills, and the ability to help multi-millionaires in Nigeria transfer funds for your profit.

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kojabu
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quote:
Originally posted by Jon Boy:
It's a frozen little lump of rock. It probably couldn't care less about its reclassification.

We shouldn't judge until we go out there and ask it.
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MyrddinFyre
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Awww, I feel bad for Pluto.
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pooka
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A Love Song about Pluto

Weird that it was recorded in 1997. I stumbled across it as a result of Rav hooking me up with eMusic.

It features a web address set to music. Try singing:
" And at the International Astronomical Union Working Group
For Planetary System Nomenclature
They too say that Pluto is a planet
reinforcing Clyde Tombaugh's view of nature."

Okay, under that definition, Neptune is not a planet because it has not cleared its orbit of Pluto. I don't know if anyone else remembers when Pluto was close to the sun than Neptune. Or maybe the astronomer was just telling us about a situation that would arise.

Oh, yeah, they just said that. Well, I don't know how Pluto will get back to planethood without bringing other things larger than itself with it.

[ August 24, 2006, 06:29 PM: Message edited by: pooka ]

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Jon Boy
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quote:
Originally posted by kojabu:
quote:
Originally posted by Jon Boy:
It's a frozen little lump of rock. It probably couldn't care less about its reclassification.

We shouldn't judge until we go out there and ask it.
Okay. I nominate you as Earth's ambassador to Pluto.
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Swampjedi
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Actually, I nominate Britney Spears.

And her second, Christina Agu.. Aga... the trashy one.

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Soara
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8, not 9 planets: Earth has finally kicked.
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Juxtapose
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Ssh, ssh, Pluto. There now, don't cry. You don't pay any attention to what those mean old astronomers say. You'll always be a planet to me.
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cmc
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*echoes Juxtapose*
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Boris
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quote:
Originally posted by Swampjedi:
Actually, I nominate Britney Spears.

And her second, Christina Agu.. Aga... the trashy one.

Which one's the trashy one?
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Ron Lambert
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There has been agitation to demote Pluto from being a planet almost since it was discovered in 1930. Apparently they had to wait until the discoverer died. That was American astronomer Clyde William Tombaugh (February 4, 1906 – January 17, 1997). He always resisted efforts to demote Pluto from being a planet in the past. He liked being able to claim he was the only living astronomer to have discovered a new planet, and he was pretty well liked and respected. But in the back of their minds, the great majority of astronomers always knew that sooner or later reason would have to prevail.
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Mig
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Check out his neat planet size comparison web page to give you an idea of just how small Pluto is. Earth's moon is bigger than Pluto.

http://www.sciencenetlinks.com/interactives/messenger/psc/PlanetSize.html

Just pick the two planets (including our moon) you want to campre and click compare. Very cool. Hours of pure fun.

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Lyrhawn
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Stephen Colbert had a really interesting guest on his show last night talking about the shape of the galaxy.

I never realized this before, and I feel stupid now for not having known, but she basically said the galaxy was a sphere, and while we usually think of the galaxy as having some border or what not, in the same way we thought sailors would sail off the map in the Atlantic, you really just curve down to the other side of the galaxy.

I guess this sort of defies all sense of Star Trek styled astronomical geography. But it helps lend a lot of helpful explanation into the nature of wormholes and such punching holes through the sphere to close the distance between two places. Conceptually it makes a lot more sense, but I never really heard it explained so simply before.

My question is then, how do you get from galaxy to galaxy? And what is in the space, if there is any, between galaxies? Is it a matter of going "up" as opposed to simply around the sphere? Much in the same way you go "up" when escaping earth gravity?

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Mathematician
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quote:
Originally posted by Lyrhawn:
Stephen Colbert had a really interesting guest on his show last night talking about the shape of the galaxy.

I never realized this before, and I feel stupid now for not having known, but she basically said the galaxy was a sphere, and while we usually think of the galaxy as having some border or what not, in the same way we thought sailors would sail off the map in the Atlantic, you really just curve down to the other side of the galaxy.

I guess this sort of defies all sense of Star Trek styled astronomical geography. But it helps lend a lot of helpful explanation into the nature of wormholes and such punching holes through the sphere to close the distance between two places. Conceptually it makes a lot more sense, but I never really heard it explained so simply before.

My question is then, how do you get from galaxy to galaxy? And what is in the space, if there is any, between galaxies? Is it a matter of going "up" as opposed to simply around the sphere? Much in the same way you go "up" when escaping earth gravity?

Galaxies themselves are relatiely flat (at least, the normal shaped ones). The universe as a whole....who knows. It's CLOSE to flat, but we're having trouble determining if it's exactly flat. It turns out that simply by assuming our universe is roughly the same everywhere and the same in every direction, there are only 3 possible shapes for it - a plane (well, 4 dimensional plane, but still), a 4-dimensional sphere, or a 4-dimensional hyperboloid.

We've pretty muched ruled out the hyperboloid case, but there is mounting evidence that our universe is in fact 4-sphere shaped (or maybe it's a 3-sphere for the spatial coordinates and something less closed for the time dimension, I don't really remember).

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Lyrhawn
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So the galaxy is still a sphere right? I mean, the earth is flat...from where I'm standing, even though I know in actuality it's a sphere.

If it isn't, what shape is it?

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pooka
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If you compare Jupiter or Saturn with Earth, Earth looks pretty ridiculous. But at least it isn't made of gas.

So do we start picking on the next smallest planet now?

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Mathematician
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quote:
Originally posted by Lyrhawn:
So the galaxy is still a sphere right? I mean, the earth is flat...from where I'm standing, even though I know in actuality it's a sphere.

If it isn't, what shape is it?

Our particular galaxy is more like a flat spiral with a bulge in the center.

Here's the best picture I can come up with.

start with a ping pong ball. Draw a circle around it. Attach one end of several pieces of REALLY long spaghetti to it and pull the sphaghetti tight (so you have a ball with a lot of lines coming out of it). Now, rotate the ball, say, 360 degrees, so the spaghetti curves. That's a decent picture of what our galaxy looks like.

For an even clearer picture, google image search "milky way galaxy"

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pooka
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I've been interested by all the discussion of Charon. I think Pluto having a moon and other satellites is compelling reason for it to be considered a type of planet. If they want to call it a dwarf planet, fine. I'm just not sure Earth doesn't deserve the same designation.
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Lyrhawn
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Does pluto have an atmosphere?
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pooka
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I don't know, but I don't think Mercury does either, and Mercury is smaller than two moons of other planets.
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pooka
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Another strike against Mercury (orbit is more important to the definition of planet than size, size is only implied in mass required to maintain a round shape)
quote:
Mercury's orbit is highly eccentric; at perihelion it is only 46 million km from the Sun but at aphelion it is 70 million. The position of the perihelion precesses around the Sun at a very slow rate. 19th century astronomers made very careful observations of Mercury's orbital parameters but could not adequately explain them using Newtonian mechanics. The tiny differences between the observed and predicted values were a minor but nagging problem for many decades. It was thought that another planet (sometimes called Vulcan) slightly closer to the Sun than Mercury might account for the discrepancy. But despite much effort, no such planet was found. The real answer turned out to be much more dramatic: Einstein's General Theory of Relativity! Its correct prediction of the motions of Mercury was an important factor in the early acceptance of the theory.

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ChevMalFet
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Wiki on Pluto's Atmosphere

Surprisingly for its small mass it does. "thin atmosphere thought to include Nitrogen, Methane, and Carbon Monoxide." So, assuming the scientific assumption is correct, it's poisonous.

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pooka
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But neither atomospher nor size were included in the definition.

I would be interested to know if Mercury could be proved to have "cleared its orbit" since its orbit is so wacky.

Clearing the neighborhood of its orbit is the parameter on which Pluto lost, but it's equally true of Neptune since their orbits cross.

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Nighthawk
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quote:
Originally posted by Mathematician:
quote:
Originally posted by Lyrhawn:
So the galaxy is still a sphere right? I mean, the earth is flat...from where I'm standing, even though I know in actuality it's a sphere.

If it isn't, what shape is it?

Our particular galaxy is more like a flat spiral with a bulge in the center.

Here's the best picture I can come up with.

start with a ping pong ball. Draw a circle around it. Attach one end of several pieces of REALLY long spaghetti to it and pull the sphaghetti tight (so you have a ball with a lot of lines coming out of it). Now, rotate the ball, say, 360 degrees, so the spaghetti curves. That's a decent picture of what our galaxy looks like.

For an even clearer picture, google image search "milky way galaxy"

I've had a teacher describe a galaxy's shape as "a fried egg in zero gravity".

Needless to say, my curriculum was weak in that regard.

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ChevMalFet
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Actually I've heard it said that Earth, Mars, Jupiter, and Neptune technically haven't "cleared their neighborhood."
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Ron Lambert
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We have to continue counting Mercury as a planet, because it conforms to Bode's Law, as do the other seven. (This is stated somewhat tongue-in-cheek.)

Bode's Law (or the Titius-Bode law) may not be an actual physical law, it is just an observation that within fairly close margins, it predicts the spacing of the orbits of the eight planets.

The following definition from Wikipedia:

quote:
As originally stated by Titius, the "law" was formulated to give the orbital radius, a, of each planet outward from the sun in units such that the Earth's orbital radius = 10, with

a = n + 4

where n = 0, 3, 6, 12, 24, 48 ..., with each value of n (after 3, which is not twice 0) twice the previous value; the resulting values were not divided by 10 to convert them into astronomical units (AU).

....

A more modern formulation is that the mean distance a of the planet from the Sun is, in AUs:


where k=0,1,2,4,8,16,32,64,128 (0 followed by the powers of two)

For the outer planets, the first term becomes more and more negligible, and the interpretation is that each planet is roughly twice as far from the sun as the last one.

This "law" was postulated when Saturn was the furthest known planet whose orbit was known. There was a gap between Mars and Jupiter. But after that, Ceres and then other asteroids were found in the right location between Mars and Jupiter, and later still Uranus was found to come where Bode's law predicted it to be, and these seemed to confirm the law. However, Neptune is a little off. Some scientists now say Bode's Law is just a coincidence, and nothing more.

quote:
Planet T-B rule distance / Real distance
Mercury 0.4 / 0.39
Venus 0.7 / 0.72
Earth 1.0 / 1.00
Mars 1.6 / 1.52
(Asteroid Belt) 8.2 / 8.277
Jupiter 5.2 / 5.20
Saturn 10.0 / 9.54
Uranus 19.6 / 19.2
Neptune 38.8 / 30.06
(Pluto) 77.2 / 39.44

Being spread out as it is, the number taken for the distance to the Sun (2.77 AU) of the Asteroid Belt is actually that of the Belt's biggest asteroid Ceres, which was at one time considered a planet as well. Ceres was considered a planet from 1801 until the 1860's. Pluto was generally considered a planet from 1930 to 2006.

Of course, the discrepancies may indicate where the solar system was disrupted at some time in the past. Close passage of a large gravitational body, such as a rogue interstellar planet or star, would be expected to affect the outer planets the most, especially Neptune.

Possibly bad news for Velikovsky buffs: Venus appears to fit right about where it is supposed to be.

[ August 26, 2006, 02:05 PM: Message edited by: Ron Lambert ]

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Gwen
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quote:
Since Neptune hasn't cleared its orbit of Pluto, doesn't that mean Neptune isn't a planet either?
By "cleared its orbit", they mean that it's the most massive object by at least five orders of magnitude in its orbit. So since Neptune is at least that much more massive than Pluto, Neptune gets to be a planet.

The definition of planet also excludes objects orbiting a point within a planet, I think, so we don't have to worry about Luna becoming a planet or something...then again, Earth/Terra's path of orbit crosses Luna's, doesn't it? And I don't think that it's that much more massive...

Anyway, yeah, it's stupid. What'll happen when we come across a Pluto-Charon-like binary-planet thing without a Neptune-like "you don't count as planets because I'm much bigger than you" planet? Which will be planets? Both? Neither?

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Tante Shvester
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I would like to nominate Pluto as a "planette". Our solar system can consist of planets and planettes.
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Lyrhawn
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I say Diet Planet.
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