Re: More Pluto Goofyness . . .
On 26/08/2009, at 9:03 AM, Ronn! Blankenship wrote: What's a planet? Debate over Pluto rages on - CNN.com No it doesn't. *sigh* Either planets sweep their orbits of debris in which case we have 14+ or they don't and we have 8. But it's not a debate about Pluto. It's a debate about whether we have lots of planets or we have some planets and some planetoids. Charlie. ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
Re: More Pluto Goofyness . . .
On 26/08/2009, at 11:24 PM, Alberto Monteiro wrote: Charlie Bell write: Either planets sweep their orbits of debris in which case we have 14+ or they don't and we have 8. Uh? Isn't it the other way around? Um, yes. :-) But it's not a debate about Pluto. It's a debate about whether we have lots of planets or we have some planets and some planetoids. I think a much more interesting debate would be to try to explain why Mars has two tiny moonlets and Venus and Mercury have none. Probably (my guess) Mars's moons are recent acquisitions, and won't last forever. Venus and Mercury may have had moonlets in the past too, that lasted a few million years and then either crashed or flew away. IIRC, Phobos is falling and Deimos is leaving Mars. ...and our moon is leaving too. It's all a matter of time. C. ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
Re: More Pluto Goofyness . . .
Charlie Bell write: Either planets sweep their orbits of debris in which case we have 14+ or they don't and we have 8. Uh? Isn't it the other way around? But it's not a debate about Pluto. It's a debate about whether we have lots of planets or we have some planets and some planetoids. I think a much more interesting debate would be to try to explain why Mars has two tiny moonlets and Venus and Mercury have none. Probably (my guess) Mars's moons are recent acquisitions, and won't last forever. Venus and Mercury may have had moonlets in the past too, that lasted a few million years and then either crashed or flew away. IIRC, Phobos is falling and Deimos is leaving Mars. And why with 100+ moons, none of them has a sub-moon? Alberto Monteiro the nostalgic ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
Re: More Pluto Goofyness . . .
Charlie Bell wrote: IIRC, Phobos is falling and Deimos is leaving Mars. ...and our moon is leaving too. No, it's not. If the Sun didn't explode [*], the Earth-Moon system would stabilize in two tidal-locked bodies. It's all a matter of time. Yes, but we are talking about a difference in many orders. The Moon has orbited Earth for thousands of millions of years, and it will orbit for ten times that number before stabilizing. Deimos may leave Mars even before Pangea Nova forms on Earth. Alberto Monteiro [*] is this the correct verbal tense? I want to express an alternate hypothetical future to a deterministic and almost sure future. ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
Re: More Pluto Goofyness . . .
On 26/08/2009, at 11:41 PM, Alberto Monteiro wrote: Charlie Bell wrote: IIRC, Phobos is falling and Deimos is leaving Mars. ...and our moon is leaving too. No, it's not. If the Sun didn't explode [*], the Earth-Moon system would stabilize in two tidal-locked bodies. Would it? The moon is drifting away at 3cm/year or so. At what distance will the moon be when terra is tidally locked to the moon? Is that distance close enough that interactions with other bodies won't eventually pull it away? [*] is this the correct verbal tense? I want to express an alternate hypothetical future to a deterministic and almost sure future. Well, the Sun isn't going to explode. It'll expand into a red giant, and then slough its outer layers leaving a white dwarf remnant. C. ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
Re: More Pluto Goofyness . . .
Original Message: - From: Charlie Bell char...@culturelist.org Date: Wed, 26 Aug 2009 22:09:46 +1000 To: brin-l@mccmedia.com Subject: Re: More Pluto Goofyness . . . On 26/08/2009, at 9:03 AM, Ronn! Blankenship wrote: What's a planet? Debate over Pluto rages on - CNN.com No it doesn't. *sigh* Either planets sweep their orbits of debris in which case we have 14+ or they don't and we have 8. But it's not a debate about Pluto. It's a debate about whether we have lots of planets or we have some planets and some planetoids. It's actually not a scientific debate, but a debate about semantics. Planetary science will not change with any change in definition, or what objects that orbit the sun we put in what boxes. To restate it, I don't know of any predictive or descriptive difference beteween the 8 or the 14+ planet cases. Both cases describe the same solar system; they just attribute different words to different sets of circumstances. Dan M. myhosting.com - Premium Microsoft® Windows® and Linux web and application hosting - http://link.myhosting.com/myhosting ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
Re: More Pluto Goofyness . . .
Maybe the 4 body problem is unstable. Sent from my BlackBerry Smartphone provided by Alltel -Original Message- From: David Hobby hob...@newpaltz.edu Date: Wed, 26 Aug 2009 11:03:02 To: Killer Bs (David Brin et al) Discussionbrin-l@mccmedia.com Subject: Re: More Pluto Goofyness . . . Alberto Monteiro wrote: Charlie Bell wrote: IIRC, Phobos is falling and Deimos is leaving Mars. ...and our moon is leaving too. No, it's not. If the Sun didn't explode [*], the Earth-Moon system would stabilize in two tidal-locked bodies. Alberto-- I'd go with doesn't, but that does make it seem like not exploding is a possibility. As for why we don't see moons with submoons, it may just be hard for moons to capture submoons. It must require a pretty close match of trajectories. ---David ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
Re: More Pluto Goofyness . . .
Alberto Monteiro wrote: Charlie Bell wrote: IIRC, Phobos is falling and Deimos is leaving Mars. ...and our moon is leaving too. No, it's not. If the Sun didn't explode [*], the Earth-Moon system would stabilize in two tidal-locked bodies. Alberto-- I'd go with doesn't, but that does make it seem like not exploding is a possibility. As for why we don't see moons with submoons, it may just be hard for moons to capture submoons. It must require a pretty close match of trajectories. ---David ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
Re: More Pluto Goofyness . . .
On Aug 26, 2009, at 8:24 AM, Alberto Monteiro wrote: Probably (my guess) Mars's moons are recent acquisitions, and won't last forever. Venus and Mercury may have had moonlets in the past too, that lasted a few million years and then either crashed or flew away. And it's entirely likely that Mars has had other moons in the past before Phobos and Deimos. I know of at least one equatorial oblique crater. IIRC, Phobos is falling and Deimos is leaving Mars. That's pretty consistent with my understanding. And why with 100+ moons, none of them has a sub-moon? My guess would be that there just aren't many stable solutions to a close-in three-body problem like that. Jupiter's gravitational effects dominate the orbital dynamics of a good part of the solar system, and many of its satellites are fairly close to its Roche limit to begin with, so my back-of-the-napkin guess would be that sub=moons would be extremely rare and tend not to be in very stable orbits. (As much as any orbit in this environment could truly be called stable, that is.) They would tend to become co-orbiting moons of the parent body before one would actually orbit the other. And co-orbiting bodies aren't entirely known even in solar orbit: http://en.wikipedia.org/wiki/3753_Cruithne http://en.wikipedia.org/wiki/J002E3 It is the mark of a higher culture to value the little unpretentious truths which have been discovered by means of rigorous method more highly than the errors handed down by metaphysical and artistic ages and men, which blind us and make us happy. -- Nietszche ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
Re: More Pluto Goofyness . . .
Bruce Bostwick wrote: ... And why with 100+ moons, none of them has a sub-moon? My guess would be that there just aren't many stable solutions to a close-in three-body problem like that. Jupiter's gravitational effects dominate the orbital dynamics of a good part of the solar system, and many of its satellites are fairly close to its Roche limit to begin with, so my back-of-the-napkin guess would be that sub=moons would be extremely rare and tend not to be in very stable orbits. Bruce-- I think there certainly are stable solutions for some planet/moon systems without submoons. The orbit of the submoon would have to be definitely inside the Hill sphere of the moon. See: http://en.wikipedia.org/wiki/Hill_sphere To me, the problem is more that it's very unlikely that objects will get captured by the moon. ---David And smaller fleas to bite them, Maru ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
Re: More Pluto Goofyness . . .
On Aug 26, 2009, at 12:10 PM, David Hobby wrote: And why with 100+ moons, none of them has a sub-moon? My guess would be that there just aren't many stable solutions to a close-in three-body problem like that. Jupiter's gravitational effects dominate the orbital dynamics of a good part of the solar system, and many of its satellites are fairly close to its Roche limit to begin with, so my back-of-the-napkin guess would be that sub=moons would be extremely rare and tend not to be in very stable orbits. Bruce-- I think there certainly are stable solutions for some planet/moon systems without submoons. The orbit of the submoon would have to be definitely inside the Hill sphere of the moon. See: http://en.wikipedia.org/wiki/Hill_sphere I stand corrected. :) To me, the problem is more that it's very unlikely that objects will get captured by the moon. Given how narrow the limits would be for all the parameters to line up to a successful capture, you're almost certainly right about that. Correct morality can only be derived from what man is—not from what do-gooders and well-meaning Aunt Nellies would like him to be. -- Robert A. Heinlein ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
RE: More Pluto Goofyness . . .
-Original Message- From: brin-l-boun...@mccmedia.com [mailto:brin-l-boun...@mccmedia.com] On Behalf Of Bruce Bostwick Sent: Tuesday, August 25, 2009 10:56 PM To: Killer Bs (David Brin et al) Discussion Subject: Re: More Pluto Goofyness . . . On Aug 25, 2009, at 6:03 PM, Ronn! Blankenship wrote: What's a planet? Debate over Pluto rages on - CNN.com http://www.cnn.com/2009/TECH/space/08/24/pluto.dwarf.planet/index.html http://www.thinkgeek.com/tshirts-apparel/unisex/sciencemath/8964/ Response: If that were in a babydoll tee, I'd be all over it. Or it would be all over me Julia P.s. I'm seriously contemplating the Totoro babydoll tee, although I could use a couple more brown shirts, which looks a lot like maybe the Chocolate Molecule one, or the Hypnotoad one ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
More Pluto Goofyness . . .
What's a planet? Debate over Pluto rages on - CNN.com http://www.cnn.com/2009/TECH/space/08/24/pluto.dwarf.planet/index.html ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
Re: More Pluto Goofyness . . .
On Aug 25, 2009, at 6:03 PM, Ronn! Blankenship wrote: What's a planet? Debate over Pluto rages on - CNN.com http://www.cnn.com/2009/TECH/space/08/24/pluto.dwarf.planet/index.html http://www.thinkgeek.com/tshirts-apparel/unisex/sciencemath/8964/ ___ http://mccmedia.com/mailman/listinfo/brin-l_mccmedia.com
