So Pluto is a planet!?

[Fingal]

The biggest problem here though is that "planet" is a historic term, created when all we knew about them is that they moved against the background of otherwise motionless stars. It's not a phenomenon that's been observed then categorised, it's an ancient term that scientists, for some reason, feel the need to retain and define. Other sciences have the same problem. Defining intelligence or emotion is an ongoing argument in neuroscience and artificial intelligence and again these are old terms that we're trying to classify rather than making observations and then applying terminology that seems most appropriate.

[John FX]

I'd rather just reclassify Pluto as a planet, then plug my ears to all criticism of this decision.

Probelm solved?

I`m with you. I don`t care about classification criteria, consistency or any of the things that have been said here so far.

Pluto is a planet and we have 9 planets. The rest lost the lottery.

[Ralathon]

What if we placed limites on the inclination?

Say we define a range of inclinations which include 95% of the mass of objects orbitin the sun.

Or... since the sun rotates (right?), we say +/- 5 degrees from the sun's equatorial plane.

Outside of that range... you can at best be a planetoid, not a planet.

I think dwarf planet isn't as good of a name as "planetoid", but it seems they also wanted a group "minor planets" (which actually includes all the asteroids...)

The clearing the orbit thing is related to size, so I can see where "dwarf" comes in, but if you put Earth in the orbit of Eris, it wouldn't clear the orbit either.

Clearly the orbit is important, its why we'd consider pluto for planet status, but not the moon.

So... why not inclination based definitions too?

Say your star system captured a rogue jupiter in a 90 degree inclined orbit. Following your definition it wouldn't be a planet.

We have a perfectly adequate definition of planet already:

- Object massive enough to be pulled into a sphere but not massive enough for sustained fusion.

- Object orbits a star.

- Object has cleaned its orbit so it contains most of the matter in that orbit.

Why would we bother changing it? In the end its just a label that we use to refer to some rocks floating in space.

[N_las]

Is really just nationalism, the states where Pluto's discoverer was born or lived passed resolutions that made it back a planet. Nobody made a fuss about Pluto being a dwarf planet in all the talks the observatory of my city gave, this is really just an issue for the US.

Thats true. I don't know anybody here in Europe who bats an eyelash about Pluto. "So it isn't calssified as Planet anymore, ok...". They react like if they heard that some weird reptile thing is now reclassified as amphibian.

The only people who react weird are US-Americans I meet on the internet: "NOOO! Why isn't it a planet anymore? !". As if the label "Planet" would be something to be proud about.

[m4v]

I`m with you. I don`t care about classification criteria, consistency or any of the things that have been said here so far.

Pluto is a planet and we have 9 planets. The rest lost the lottery.

How very scientific. Using science and discarding it at one's convenience is not really an appropriate thing to do.

[ZetaX]

I trained as a geologist, so from that perspective it's difficult to see how they aren't.

Your training as a geologist might not have trained you to recognize the fact that they orbit a planet. After all, earth's geologists needed until Galileo to figure such a thing out.

But seriously, if geology is your main definition, then Jupiter is no planet, for it is completely lacking geology.

[Hannu]

We have a perfectly adequate definition of planet already:

It is adequate only in our current system as it is known today.

- Object massive enough to be pulled into a sphere but not massive enough for sustained fusion.

These are quite clear limits in our current system, but no natural law disables objects in both limits. So, if we would want to use this for every possible solar systems, we should define what is "sphere" and how much fusion energy production is accepted. And is it planet, if there was fusion of natural deuterium in history, but it have ceased to be significant energy source. Exact limits do not work because any object in nature is not perfect sphere and there is low but finite probability that two atom nucleii fuse even in normal temperature and density, so probably fusions have happened even in Jupiter's massive hydrogen mass.

- Object orbits a star.

It is easy to imagine endless arguing is brown dwarf star or planet, if such object would be in our solar system.

- Object has cleaned its orbit so it contains most of the matter in that orbit.

This is also artificial limit, which is practical on known parts of our solar system. If we would be strict, Earth would not be a planet, because some people is worried about near earth asteroids. How about synchronized stuff, like trojans or Pluto versus Neptune? There could be very massive planets in outer solar system, which wave not had enough time to clear their orbits.

Why would we bother changing it? In the end its just a label that we use to refer to some rocks floating in space.

Because we all have human tendency to classify everything and we have different opinions how this classification should be done.

[Albert VDS]

Any smaller outer system bodies would get a tail if put in earth orbit at least unless mars sized or larger as the cold let it freeze gas who would escape.

Then I thought that putting anything other than rocks very close would give this results, has some hot Jupiters with tails.

But they wouldn't loose 2/3 of their mass. But of course you could argue, again, that if you put anything close enough it would loose more than 2/3 of it's mass.

And the cute picture is a cartoon and uses cartoon sizes, a cat in a cartoon is larger than an mouse but not 8 time larger.

I know it's the artists freedom to make it a different size, but it also gives the people who don't know any better the idea that it's almost as big as Mars.

If it looks almost as big then it must be a planet.

Can anyone give a real reason, one that makes sense, why Pluto needs to be named a planet? The only reasons I read is that they just want it to be a planet, which isn't a really good reason for anything.

[Hannu]

So would anything if put close enough

These funny images are very misleading. Celestial bodies have not changed in couple of billions of years. Only it has, how funny little aliens on one of the planets classify them.

[lajoswinkler]

Is really just nationalism, the states where Pluto's discoverer was born or lived passed resolutions that made it back a planet. Nobody made a fuss about Pluto being a dwarf planet in all the talks the observatory of my city gave, this is really just an issue for the US.

I think a lot of folks know Pluto was discovered by someone in USA, and I remember those "protests" with a quite nationalistic (not patriotic, mind that!) accent.

Basically nobody outside USA gives a flying crap about the new classification. It's popular to be butthurt in USA only.

[rtxoff]

Now there is this International Astronomical Union which decided it was time to redefine the word planet. They consist of more then 10000 individual members from all around the world (all of them astronomers Ph. D. level and beyond) and they had a vote. So really (not really just sarcastic) , what kind of impudence was it when they decided doing this, especially when many of us learned that pluto is an planet in school.

In such types of discussions you just won't find a solution which will satisfy everybody however i think IAU has found a solution i can live with and it was time to change it.

What cannot be settled by experiment is not worth debating.

[KerikBalm]

Say your star system captured a rogue jupiter in a 90 degree inclined orbit. Following your definition it wouldn't be a planet.

We have a perfectly adequate definition of planet already:

- Object massive enough to be pulled into a sphere but not massive enough for sustained fusion.

- Object orbits a star.

- Object has cleaned its orbit so it contains most of the matter in that orbit.

Why would we bother changing it? In the end its just a label that we use to refer to some rocks floating in space.

And yet, such an object would be clearly different from the rest.

The rest would have formed from the accretion disk of our star, that 90 degree inclined body captured from extrasolar space did not form in this way.

We could have "regular planets" (or "Major Planets" as someone else suggested), and irregular planets.

Inclinations: Sun's equator/Invariable plane

Mercury: 3.4/6.3**

Venus: 3.8/2.2

Earth: 7.2/1.6

Mars: 5.6/1.7

Ceres: ?/9.2***

Jupiter: 6.1/0.3

Saturn: 5.5/0.9

Uranus: 6.5/1.0

Neptune: 6.4/0.7

Pluto: ***11.9/15.5 ***

Eris: ***43.9*** (I don't know if this is the ecliptic, solar equator, or invariable plane, but when its this large, it doesn't really matter).

We could easily arrive at the same set of "true planets" using the inclination to the invariable plane as the objective (though still somewhat arbitrary) criteria, instead of "clearing its orbit"

If we order the inclinations of the "round" bodies, and take the Standard deviation of the gas giants, Earth is within 2 sigma of the inclinations of the most inclined gas giant.

If we use 2 sigma as the cutoff for an iterative inclusion, incorportating Earth into the list of planets then gets in all the other inner planets except mercury.

If we use the average+ a multiple of the st dev, then we need to use a multiple of 3 to incorporate Earth (otherwise, only the gas giants meet the criteria), but by incorporating earth, we then have to incorporate Mars and Venus... Mercury still doesn't make the cut.

I'd have to go to 8 standard deviations to incorporate mercury... but then by doing that, ceres, pluto, and even Eris make the cut....

Unless we "weight" the inclinations in relation to the planets mass

Maybe Mercury shouldn't be a planet?

We could arbitrarily say that somewhere between 6.3 and 9.2 is the limit, but I like a statistics/standard deviation based approach.

But if this "cleared the neighborhood" approach gets a separation of 5 orders of magnitude between planet and non-planet, then I will support it.

But my point is that the inclinations can be used to draw a clear distinction between the inner and outer planets, between Mercury and the rest of the inner planets .... and between the "regular planets" and the currently named "dwarf planets" (although its hard to incorporate Mercury in the "regular planets" with this metric.)

Edited October 3, 2014 by KerikBalm

[DarkStar64]

sorry for spamming but...

pls everyone here just watch is.

[magnemoe]

I know it's the artists freedom to make it a different size, but it also gives the people who don't know any better the idea that it's almost as big as Mars.

If it looks almost as big then it must be a planet.

Can anyone give a real reason, one that makes sense, why Pluto needs to be named a planet? The only reasons I read is that they just want it to be a planet, which isn't a really good reason for anything.

The reason is that everybody have learned its a planet so why should it be demoted, nobody remember that Ceres was one so its not very relevant.

I agree that the size difference between Pluto and Mercury/ Mars is misleading.

And yes I know the real reason, we have found many dwarf planets in the cupier belt and will find lots more, why should only Pluto be included in the public lists?

It would end up calling the current 8+ pluto + perhaps 1 other the major planets and the +200 other for planets.

Probably part of the problem with Ceres back in the 19th century, they found it, then they start finding lots of asteroids, where to put the bar, they decided to exclude it but could just have included as the next one on list is far smaller but they did not know.

[Albert VDS]

The reason is that everybody have learned its a planet so why should it be demoted, nobody remember that Ceres was one so its not very relevant.

That means we need to believe these things because we learned them in school:

- The tongue taste map

- Diamonds are made from coal

- van Gogh cut off his own ear.

- Einstein couldn't do math.

- Benjamin Franklin discovered electricity by flying a kite which got struck by lighting.

- Newton discovered gravity when an apple dropped on his head.

- Columbus discovered that the Earth was round.

- Napoleon was short.

- Edison invented the light bulb.

Some of the things I could think off.

[lajoswinkler]

That means we need to believe these things because we learned them in school:

- The tongue taste map

- Diamonds are made from coal

- van Gogh cut off his own ear.

- Einstein couldn't do math.

- Benjamin Franklin discovered electricity by flying a kite which got struck by lighting.

- Newton discovered gravity when an apple dropped on his head.

- Columbus discovered that the Earth was round.

- Napoleon was short.

- Edison invented the light bulb.

Some of the things I could think off.

Who teaches this crap?

[PakledHostage]

Who teaches this crap?

The same people who teach that "evolution is just a theory"?

[Red Iron Crown]

The same people who teach that "evolution is just a theory"?

Evolution is just a theory. The problem lies in misunderstanding what a theory is in a scientific context.

[ZetaX]

Who teaches this crap?

The same teachers that tell you centrifugal forces don't exist.

[N_las]

My teacher in ~7th grade told us that seasons are caused by the earths elliptical orbit: If the Earth is at its closest to the sun, we have summer.

And the phases of the Moon are caused by the shadow of the Earth.

[ZetaX]

Are you at least living in australia¿

[Mr Shifty]

Who teaches this crap?

For real? You seriously have had a cultural education that includes no mythology? I've heard all of those canards at one time or another; in some cases they're not 'crap' so much as a cultural shorthand, e.g. Newton's apple represents inspiration, Edison's invention (he may not have invented the light bulb, but he did create the first practical and manufacturable version of it) represents ingenuity, etc. I can think of many other falsities that underlie almost all of human knowledge: categorization and generalization is the best way to gain systemic understanding, language can convey precise meaning, history is a chained series of causal events, etc. Part of becoming a thinking, reasoning person is discovering how and when the mythologies we absorbed in our chrysalis are and were useful, and when not. But scoffing at them, and particularly scoffing at the supposed cultural naivety of others from afar, is almost never useful.

Edited October 3, 2014 by Mr Shifty

[PakledHostage]

Evolution is just a theory. The problem lies in misunderstanding what a theory is in a scientific context.

I realise that (and I think you realise that I realise that), but the problem is how it is presented. There's a clear bias. Just as there's a clear bias behind the "Pluto is a planet" agitators.

[N_las]

I learned more science from german public television broadcasting than from my teachers. We have this great show: "Sendung mit der Maus" (Show with the Mouse).

They had a great broadcast about space travel over 20 years ago. I can't find it on the internet :/

But I found this snippet: It isn't that old, and it gives a nice idea about the format of the show. I recomment watching it, even if you don't understand a word. It is entertaining as hell.

https://www.youtube.com/watch?v=mOORih_yfkU

[Hannu]

My teacher in ~7th grade told us that seasons are caused by the earths elliptical orbit: If the Earth is at its closest to the sun, we have summer.

I am envy about quality of your teaching. My teacher "knew", that we have so cold in Finland, because north latitudes are so much farther (several thousands of kilometers) from the Sun than the equator, and demonstrated it with a slide projector and a globe. Fortunately I had already learned (through the hard way, as real nerd without social skills must do) that it was better to be quiet and not ask "how about the fact that Earth is 5 millions of kilometers closer Sun in January than in July". I was then about 9.