[X] My Assistant

[paxdan]

For all interested in sizes i made 2 little Diagramms.
The First contains earth, some moons, biggest planetoids, some tno ect.

All sizes of all shown bodies are correct and in the same scale to each other as far as known.
Of course there it is not made public a definite diameter of 2003 UB313, 2005 FY9 und 2003 EL61 ( +b ).
2003 UB313 has a diameter of 2800km ( latest status ) in my graphic.
2005 FY9 has 1600km, 2003 EL61 has 1500 km with b aprx. 250km.

How small Enceladus is, but so activ...
So size does not always matter...

Nice one, err how about including a single pixel width yellow curved line to indicate the size of the sun for comparrison too.

[abalone]

There was a time when culture said the earth is the centre of the universe and the sun as everything else rotates around it. That cultural icon was challenged by science with a nice mesure of success.

It would be a shame to let culture intimidate science.

Good try but not the same. In your example scientific discovery was totally in conflict with the established culture. The two were mutually exclusive.

With planets it is only a slightly different interprtation between "culture" and a group of astronomers who cant even present a uniform position in scientific literature.

I am not sure that the population at large would be convinced that the Earth is not the centre of the universe and the sun as everything else rotates around it, if half the scientific community was telling them it is.

[ljk4-1]

Nice one, err how about including a single pixel width yellow curved line to indicate the size of the sun for comparrison too.

And don't forget how active Triton is. Maybe it's just thanks to Neptune, but it makes one wonder what is going on in the Pluto-Charon system.

[odave]

If I were designing a roster of solar system entities for fifth grade classrooms for the 2006-7 school year...

One thing I've discovered about elementary age kids, after doing astronomy nights and LEGO robotics with them, is that they are a lot smarter and more sophisticated than many adults give them credit for. And they really seem to appreciate an adult giving them an honest "we don't know for sure" answer.

So I'd give them JRehling's curriculum through Neptune and then "take the bull by the horns" with them on Pluto and KBOs. I'd explain the reasoning behind both sides of the planet/not planet debate, then ask them what they thought. It would be a great exercise in observation, logic, reasoning, testing hypotheses, and debate. From what I know of fifth graders, they can certainly handle the ambiguity and would delight in knowing that their opinion is as good as anyone else's.

[Rob Pinnegar]

"Everyone should ignore the distracting debates of the scientists, and planets in our Solar System should be defined not by some attempt at forcing a scientific definition on a thousands-of-years-old cultural term, but by simply embracing culture," says Brown. "Pluto is a planet because culture says it is." And, he adds, that means his new find is a planet too.

That's a terrible argument. It would make astronomy one big Appeal to Popularity.

A hundred years ago, a paleontologist discovered and described a dinosaur he christened "Apatosaurus". His work was ignored. Just after that, somebody else found another skeleton of the same dinosaur and named it "Brontosaurus". For a century, in the public mind, "Brontosaurus" was synonymous with "dinosaur".

Then somebody ran across the original discovery, and made people aware of it. The paleo community immediately changed the name to Apatosaurus. Why? Because the first discoverer gets naming priority, and they weren't about to change the rules to accomodate Joe Sixpack's idea of what a dinosaur should be called.

If astronomers are going to "embrace culture", then they'd better be ready to call themselves "astrologers", learn to read horoscopes, and accept people like Hoagland into their ranks. I agree that it's bad form to unnecessarily confuse the public -- but if it's necessary, then do it. Let's face it, they're going to be confused most of the time anyways.

[Guest_Myran_*]

ljk4-1 said: And don't forget how active Triton is. Maybe it's just thanks to Neptune, but it makes one wonder what is going on in the Pluto-Charon system.

Neptune have a mass just so many times larger than Triton, and Tritons orbit are retrogade and eccentric - so theres some energy getting pumped into Tritons interior by constant flexing.

Pluto and Charon are -comparatively speaking- almost of the same mass, in addition it is thought that they always show the same face against each other.

So the tidal flexing will be quite limited, but there are some other things we might find thats unique. It have been speculated that Pluto and Charon might exchange a bit of Plutos thin atmosphere. Yet it have started to freeze as Pluto moves away frmo the sun and when New Horizons get there it might be so thin that we might not be able to find if that truly occurs.

[centsworth_II]

Rather than embracing culture, why not embrace history? The nine original planets can be focused on in an historical context the same way the the thirteen original colonies enjoy a special place in american history. The discovery of additional planetary objects opens a new era in the study of the solar system and these objects are separated historically as well as spacially from the original nine. I see no problem with "The NIne" maintaining a special place no matter how many other planetary objects are discovered orbiting our sun.

[JRehling]

One thing I've discovered about elementary age kids, after doing astronomy nights and LEGO robotics with them, is that they are a lot smarter and more sophisticated than many adults give them credit for.  And they really seem to appreciate an adult giving them an honest "we don't know for sure" answer.

Honest question: Is that a random sample of all kids that age, or are those the ones who choose to show up for astronomy night and LEGO robotics? It's a wide bell curve. With ability not the only independent variable.

Your proposed discussion does sound good, though.

[ljk4-1]

Honest question: Is that a random sample of all kids that age, or are those the ones who choose to show up for astronomy night and LEGO robotics? It's a wide bell curve. With ability not the only independent variable.

Your proposed discussion does sound good, though.

I sometimes volunteer at the local observatory on their open house nights. When Mars was at its closest in 2003 (the real close encounter , I recall that one of the few people who really seemed to know what was going on (at least out loud) was a 4-year-old boy.

To top it off, when I asked him what he thought made the Red Planet red (I know, it doesn't look red in the telescope, but never mind here), he suggested the lava from the volcanoes there. I got the impression that his parents and others around him didn't even know Mars had volcanoes, let alone even bother to speculate as to why the planet's surface looks as it does.

I just hope his intelligence and sense of wonder isn't totally destroyed by our so-called educational system.

[JRehling]

That's a terrible argument. It would make astronomy one big Appeal to Popularity.

[...]

If astronomers are going to "embrace culture", then they'd better be ready to call themselves "astrologers", learn to read horoscopes, and accept people like Hoagland into their ranks. I agree that it's bad form to unnecessarily confuse the public -- but if it's necessary, then do it. Let's face it, they're going to be confused most of the time anyways.

One thing I'd like to add is that we should remember what topic astronomers are experts on. (Or, let's say, planetary scientists.) They know scads about how worlds evolve, what sort of dynamic properties ruled them in the past and continue to rule them in the present. They are very familiar with the bulk and trace properties of the worlds in our solar system. That doesn't mean they are particularly skilled at taxonomizing, categorizing, naming, etc., even though they have the facts at hand that a taxonomist would make use of.

I heartily recommend George Lakoff's narrative in his book "Women, Fire, and Dangerous Things" concerning a debate in biology over taxonomies (and biologists are presumably much more practiced in taxonomy than astronomers!). Perhaps by being so close to the subject matter, the biologists seem to have missed some essential points -- in my opinion, Lakoff, a linguist who is undoubtedly farther from the biological facts, cuts the Gordian knot at the center of the debate, identifying it as not really a debate at all.

Astronomy circa 1959 had an easy time of it. There were 9 known things Mercury sized or bigger (Pluto was supposed to be that size); uncounted stars, each far bigger than Jupiter; a collection of smaller asteroids, none more than a fraction of Mercury's diameter; and dozens of natural planetary satellites, in no case within a factor of 80 of the mass of its primary. The only bumps in the road were that 2 or 3 satellites of giant planets were bigger than Mercury, and that the whole comet-asteroid distinction was a bit puzzling. But overall, I would say that professional astronomers were less acquainted -- needed less to be acquainted -- with tough taxonomical decisions than did a baker, a mapmaker, or a bricklayer. When the time has come that some tough decisions confront the field, there's no reason to suppose that the inside people with the facts will easily and triumphantly rise to the occasion because they have the facts -- it's quite easy to find a way to get tripped up in the facts, uncertain of what to cling to when the easy categorizations fail.

In short, I'm not sure if a room of astronomers with votes to cast would do a good job settling this if they had to vote off the cuff. I have a better feeling that with some good discussion, those who have better things to say about it will get to sway the mass of astronomers and come up with something that will filter well through elementary school teachers and journalists and end up being a way to describe our corner of the universe in a way that makes it accessible for as many people as possible.

[odave]

Honest question: Is that a random sample of all kids that age

True, that is a fairly specialized group of kids, and some are certainly better at processing ambiguities than others.

Another sample I deal with on a regular basis is my 8 year old daughter and her buddies, whose interests run mostly to princesses, unicorns, and jump-rope songs. There too I have found that when I respond with "we don't really know, what do you think?", it usually results in a lively conversation.

I still think it's good to try to tackle these kinds of questions with children openly. Anything to get their brains switched on

[volcanopele]

I'll be blunt, I couldn't care less about this whole, planet/not a planet/what is a planet? debate. Personally, I think the whole thing is moronic. It has become obvious within the satellite systems of the outer satellites that size doesn't matter when it comes to how interesting an object is. I'm sure no one would argue that Rhea is a more interesting, scientifically, world than Enceladus, despite having a radius 3x that of a world that appears to be active. Mercury is surely not more interesting than Io, the moon more than Europa. And what does it matter what crowd you hang out with? Whether an object is with not so much smaller objects or ones that are MUCH smaller than you. Or whether you go around in a funny orbit, when it is so easy to go from a normal orbit, go by Neptune, and be in an inclined orbit.

So all this debate is just silly. If you seperate every thing into planets and non-planets, just make Pluto the cut-off and be done with it. If there turns out to be many objects in the KB that are larger than Pluto, then just not have school children learn all of them. It's not like they can look up in the night sky and see any of them. You just teach Pluto as the typical planet in the far outer solar system and say that there are X number of other planets as well as many more smaller objects orbiting in that region.

I agree with Mike Brown, "planet" is a culural term. As astronomers and planetary scientists uncovered the true complexity of the solar system in the last 40 years, "planet" ceased becoming an important term for describing what we are seeing scientifically.

[tedstryk]

I agree with Mike Brown, "planet" is a culural term.  As astronomers and planetary scientists uncovered the true complexity of the solar system in the last 40 years, "planet" ceased becoming an important term for describing what we are seeing scientifically.

Well, if you think about it, it never really was....the five planets were just those stars that moved that the ancients saw. When Uranus and Neptune were discovered, it was realized that they were similar, just more distant and hence fainter and so they were added. The problem happend with Ceres and the asteroids, as it was decided that they were too small. When Pluto was discovered, it was assumed its albedo was much less than it is (Additionally, since Charon wasn't discovered until 1978, most observations combined the light from the two worlds, making it seem brighter and hence larger), and I remember reading in a old book from the 1960s that it was 6,000 miles across! Now it appears that there is no size chasm between the inner rocky worlds and the worlds called asteroids and comets (I am assuming that, based on the way things are going, we probably haven't found the biggest of these worlds yet). The fact that the eight planets outsidet the Kuiper belt vary so much in size is a problem in and of itself - the ancients would have never realized that. I mean, in many ways Mercury has more in common with Ceres and Vesta than it does Jupiter.

The category was one made in ancient times. Neat models were made, in which the all the planets orbited in perfect circles with earth at the center. Secondary circles were made to compensate for discrepencies. When the Copernican revolution occured, the sun displaced earth, but the perfect circles continued until Kepler showed that orbits were elliptical. The powers that be were then angered as the telescope showed features on the moon, and then the planets, and worse, changing features - they were not perfect, changeless orbs. Also, some of them had moons of their own. People tried to make sense of this, and ideas like Bode's law seemed to make sense of planetary distances (a great coincidence). Theories developed that beginning with Earth having one moon, the patern would go 2 (Mars), 4(Jupiter), 8 (Saturn - the fact that Saturn and the planets beyond it didn't have that many known moons was at the time linked to their distance - surely they would be found!) and so on. The discovEventually, as I said earlier, two outer planets were discovered and the four outer planets were found to be the gas giants, very unlike the rocky worlds of the inner solar system. The discovery of the asteroid belt damaged this still relatively neat solar system, but this was turned backwards....the problem with Bode's law was that it predicted a planet between Mars and Jupiter - so it was assumed that this was it, but it had simply been smashed to rubble. Pluto became the odd-man-out, perhaps an ejected moon of Neptune. My point in all this is that our insistance on order in the solar system a deeply engrained cultural thing - people like order in the cosmos. Today, President Bush suggested intelligent design be taught in schools - a reminder of this. However, it now appears the ancient's view of the solar system is suffering yet another blow - It appears that the solar system is a messy place, with all sorts of objects lurking in its outer reaches. And we may have to redefine or abandon the word planet...If we were forced to re-categorize all the worlds in the solar system with no memory of tradition, it is unlikely that the gas giants would have ever been put in the same category as rocky worlds anyhow - it is scientific nonsense. In fact, Uranus and Neptune are quite different from Jupiter and Saturn, and push-come-to-shove, Jupiter is a borderline brown dwarf.

[Phil Stooke]

I haven't read the whole discussion here for lack of time, so I apologise if this repeats something already said.

One problem: people want definitions to be fences: a fence around certain objects called planets, another around objects called comets and so on. A fence definition is like 'over 2000 km diameter' or 'within 5% of being spherical' - a simple unambiguous test to decide if an object is in or out.

This worked in the 19th century! we then knew so few objects that a simple fence could surround each class of object. But now it doesn't work very well. In truth, the solar system has a complete spectrum of sizes, dust to Jupiter... a complete spectrum of shapes from Kleopatra to... uh.. Venus, a complete spectrum of ice versus rock composition and so on.

In this fuzzy universe, definitions really deal with core characteristics... they define a core and every object is a certain distance from it. Planets are large and orbit the sun... moons orbit planets... asteroids are small, rocky, and orbit the sun... comets are small, icy and orbit the sun. Then you look at a real object and it might have characteristics of several classes. Enceladus is a comet orbiting in its own tail (the E-ring)...

None of this helps... but we can't get too hung up on definitions because they are too fuzzy. I prefer to think of the word planet as a traditional designation with no very firm scientific definition. Pluto is a planet because since it was discovered it was called one. But all these objects are 'worlds'... to me.

Phil

[Guest_BruceMoomaw_*]

Oh, don't be such a party-pooper, Phil. If the "news" media don't have this debate to talk about perpetually, they'll have to limit themselves to covering runaway brides.