Re: How many planets?

rich hammett wrote:
Minun olisi pitänyt tietää, olisi pitänyt tietää,
olisi pitänyt tietää KUKA SINÄ OLET, stephenj:

Charles Beauchamp wrote:


it did seem like by the definition they are using the Moon over Earth should be a planet too. I don't get it.


no, because part of the proposed definition it that the object "is in orbit around a star, and is neither a star nor a satellite of a planet".


Well, if you read more carefully, the fact that Pluto and Charon orbit
a common center that is between them is part of the reason Charon is
considered a planet under this definition.

oops, should have read more carefully.

However, IIRC the earth-moon
barycenter is actually beneath earth's surface, so that would be a
judgement call.

i guess anything with any grav-pull at all will move the 'barycenter' from the exact 'middle' of the bigger object, right? i mean, even though the sun is millions (or whatever) of times more massive, the earth and sun's barycenter isn't in the exact core of the sun, but probably a few hundred yards from it, no?

pluto is obviously tiny, and charon's diameter is just 1/2 of pluto's and its mass is about 1/7 that of pluto, meaning it's freaking tiny. making charon a planet on the basis that the barycenter isn't inside of pluto would seem kind of silly, no?

as others have noted, pluto doesn't stack up to the other planets, but it has becoming culturally accepted as a planet. since there's no scientific issue at stake here, there's no compelling reason to come up with a 'consistent' definition by ushering in 3 or 100 more objects just because they meet some arbitrary criteria that pluto meets.

keep pluto as a planet under a grandfather clause and forget about the rest.

but by that def if saturn orbitted jupiter it wouldn't be a planet, which would seem rather weird.


size - pluto's small size, namely - seems to be what irks folks who are irked about pluto most, and iirc the earth's moon is bigger than pluto.


Don't believe it's bigger, but it's heavier.

it's got a much larger diameter (3476 km) than pluto (2274 km), and the moon's mass is 1/80 that of earth, pluto's is 1/400 that of earth. so at least by those two metrics, the earth's moon is far bigger.

we're one of the smaller planets, but we've got a moon to be proud of!

--
"when i visited Aden before collectivization,
all the markets were full of fish product. After
collectivization, the fish immediately disappeared."

- Aleksandr Vassiliev, Soviet KGB official
.

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