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dhd40
2007-Jul-09, 08:39 AM
Recently, we have seen the new dedifition of “PLANET”. But what´s the actual definition of “MOON”. Here (http://saturn.jpl.nasa.gov/science/moons/index.cfm) it says “To date, 48 moons (of Saturn) have been officially named“. I remember to have read that there are “some 80 moons” around Saturn. Now my question is: What are the criteria for a celestial body to be called a MOON? Is it size, or mass, or …? Especially around Saturn I would expect (almost) any size between Titan´s and dust/ice particle sizes. Is that true?

astromark
2007-Jul-09, 09:54 AM
I think i can safely say that a moon is a natural satellite. The unanswered part of your question would seem to be 'How small' can a moon be?
Those particles of ice that are Saturn's rings are not moons as such. Lets go Google this....>

formulaterp
2007-Jul-09, 11:39 AM
I have a horrible feeling that we are opening up a nasty can of worms which will inevitably result in the IAU reclassifying the Moon as "Major Solar System Satellite 1969A".

grant hutchison
2007-Jul-09, 11:55 AM
:DThe mismatch between the count of Saturn's discovered moons (63 at present) and named moons (48 at present) is because it takes time for the IAU to approve new names, so at any one time there are usually a number of nameless moons indentified by numbers describing their discovery circumstances.

I don't know if the cut-off between "moon" and "ring particle" has ever been given an official value; I suspect not.
("Clearing its orbital neighbourhood" might be involved :D: moons within the ring system create gaps by their gravitational interactions with the ring particles.)

Grant Hutchison

NEOWatcher
2007-Jul-09, 12:12 PM
I thought that I saw this being discussed along with the Pluto fiasco. But; I may be thinking of moon vs double planet discusions.
Anyway; I did a quick search, and there is an old thread with that exact question.
What is a moon? (http://www.bautforum.com/showthread.php?t=21505)

It gave me a chance to use the new Google search...Thanks.

George
2007-Jul-09, 12:53 PM
("Clearing its orbital neighbourhood" might be involved :D: moons within the ring system create gaps by their gravitational interactions with the ring particles.) :) Nice one!

Yet, they don't clear out each other; we have shepherding moons. These must be dwarf moons. ;)

Jeff Root
2007-Jul-09, 12:54 PM
Yes, this has been discussed previously. I didn't look at that
discussion again to refresh my memory -- in particular, whether
and to what extent I was involved.

A moon is a body orbiting a body smaller than a star. So, for
example, the MESSENGER spacecraft will become a moon of
Mercury once it goes into orbit of that planet. An artificial moon,
obviously. And a very tiny moon, obviously. Phobos and Deimos
are very tiny natural moons of Mars. They probably once were
independent asteroids orbiting the Sun. Now they are moons.

All the particles of Saturn's rings are moons, too. Or moonlets,
if you like. Very small moons. There happen to be a vast number
of them. It also happens that nobody has ever got close enough
to any of them to be able to single out an individual and track it
for any length of time. Or at all, even. Unless you count the tiny
shepherd moons as ring particles. I see no reason not to. They
are very tiny moons and exceptionally large ring particles. What
makes the shepherd moons exceptional is that they are big enough
to detect as individuals from a distance, track them for some time,
and -- most significantly -- find them again after not watching
them for a while. And identify which is which, by their positions
and / or appearance.

-- Jeff, in Minneapolis

grant hutchison
2007-Jul-09, 01:03 PM
Some, including the contributors to the Oxford Dictionary of Astronomy, would reserve the word "moon" for a natural satellite, and would therefore call Messenger an artificial satellite, but not a moon. It's a distinction I've seen made often, and one I find useful. Otherwise "moon" becomes a mere synonym for "satellite".

Grant Hutchison

NEOWatcher
2007-Jul-09, 01:08 PM
Some, including the contributors to the Oxford Dictionary of Astronomy, would reserve the word "moon" for a natural satellite, and would therefore call Messenger an artificial satellite, but not a moon. It's a distinction I've seen made often, and one I find useful. Otherwise "moon" becomes a mere synonym for "satellite".
Personally, that is the way that I have seen it referenced. Unfortunately, the media has other ideas, and that's were common references usually end up coming from.

A great (relevant) example was the Apollo 7 Sat-IVB (http://en.wikipedia.org/wiki/J002E3) being reported as "Earth's new moon".

George
2007-Jul-09, 01:09 PM
Yes, this has been discussed previously. I didn't look at that
discussion again to refresh my memory -- in particular, whether
and to what extent I was involved. Yes, there is much on this here in several threads. [I eschewed these sometimes frivolous discussions as I was occupied with the more serious effort of determining the Sun's color. ;) If any moons are labeled yellow dwarfs, please inform me a.s.a.p. :)]


All the particles of Saturn's rings are moons, too. Or moonlets,
if you like. I like. :) Is there a summarized list of all the potential terms somewhere?

Jeff Root
2007-Jul-09, 02:16 PM
Some, including the contributors to the Oxford Dictionary of Astronomy,
would reserve the word "moon" for a natural satellite, and would
therefore call Messenger an artificial satellite, but not a moon.
It's a distinction I've seen made often, and one I find useful.
Otherwise "moon" becomes a mere synonym for "satellite".
Why "mere"? You got something against synonyms? Or satellites?

"Satellite" was originally applied as a synonym for "moon".

So you'd like "moons" to be a subset of "satellites" in English?
Where a "moon" is a natural satellite?

Would there also be terms for natural rainbows as opposed to
artificial rainbows? Or natural clouds as distinct from artificial
clouds? Or natural channels as opposed to artificial canals...
err... um, okay, we've already got one for that.

Arthur C. Clarke wrote a book, published in 1957, titled "The
Making of a Moon". Guess what kind of moon.

"The Brick Moon" by Edward Everett Hale, published as a serial
in 'The Atlantic Monthly' in 1869, described the construction,
launch, and life aboard an artificial Earth satellite.

While I generally use the terms exactly as you suggest, there
is a long history of the word "moon" being used as a synonym
for "satellite", whether natural or artificial.

-- Jeff, in Minneapolis

NEOWatcher
2007-Jul-09, 02:26 PM
Why "mere"? You got something against synonyms? Or satellites?

"Satellite" was originally applied as a synonym for "moon".

So you'd like "moons" to be a subset of "satellites" in English?
Where a "moon" is a natural satellite?
And, to just make matters worse, there have been various uses of the moon vs a moon.
So; I wonder if an official definition will really change things. :think:

R.A.F.
2007-Jul-09, 02:28 PM
The Moon is the name of Earth's natural satellite...other planets natural satellites have names of their own. (even though they are rather commonly called "moons")

Calling other planets satellites, "moons" is exactly like calling Venus, Mars, etc., "earths".

Paul Beardsley
2007-Jul-09, 02:54 PM
Just to add my two pen'orth, I think if one is talking in technical language, I think the term "natural satellite" should be used for, say, Europa or Titan, and "artificial satellite" for an orbiting space probe. "Moon" should be reserved for Earth's natural satellite.

But if one is letting one's hair down, or speaking poetically, then "moon" may be used for any world orbiting another world. I would go on to say, don't use the word "moon" to describe anything artificial unless it is being regarded as a world in its own right. For instance, Skylab and the ISS were worlds to the people living there. Even then, though, it doesn't really resonate.


Calling other planets satellites, "moons" is exactly like calling Venus, Mars, etc., "earths".
Technically maybe, but poetically not.

I think if we ever call another planet an "earth" it will be because it shares crucial characteristics with our own world. Whereas "moon" sort of indicates what it is, not who it is, if that makes any sense. That is, "Moon" is not the moon's personal name in the same way that "Earth" is the Earth's personal name.

BTW are there any known moons of moons?

Jeff Root
2007-Jul-09, 03:22 PM
Is there a summarized list of all the potential terms somewhere?
Ironically, I must ask you to specify what kind terms you mean.
Give me a list of things that you expect to be on the list.

I have seen at least two fairly extensive online glossaries of
astronomical terms. At least three of the introductory astronomy
textbooks on my bookshelf have largish glossaries. And I have
accessed the Facts on File Dictionary of Astronomy at a library.

I have a page that I photocopied from a book decades ago
(Isn't it astounding that photocopiers have been around for
decades, now? I think so.) which shows "A Classification of
Material Systems" which was done by some well-known astronomer
of an even earlier age. Unfortunately it doesn't say who that
was on the photocopy and I can't recall. Walter Baade, perhaps,
or Vesto Slipher, or possibly Otto Struve? I don't feel like
retyping it right now, but maybe later. It is a bit interesting
but doesn't really contain much useful information. It isn't a
big list of terms. I've got a web page in development that
sorta parallels much of that photocopied page. It will be
titled "Stuff in Space", and connected to another page titled
"Meteoroids vs Asteroids", which I really should finish.

-- Jeff, in Minneapolis

TrAI
2007-Jul-09, 03:36 PM
I expect that some definition could be made, perhaps something along the lines that a moon is a natural object with an orbit that has a barycenter that is inside an object classified as a planet(could perhaps also be extended to dwarf planets and so on). If the barycenter was outside, it would be a binary system.

Of course, there would still be the problem of smallest size to be counted as a moon...

Paul Beardsley
2007-Jul-09, 04:11 PM
a natural object with an orbit that has a barycenter that is inside an object classified as a planet
Sounds good to me.

grant hutchison
2007-Jul-09, 04:13 PM
Why "mere"? You got something against synonyms? Or satellites?You've got a problem with "mere"?


"Satellite" was originally applied as a synonym for "moon".For sure. And it's a pretty common evolution in English that Latinate and Teutonic derivations develop their own specialist uses.


So you'd like "moons" to be a subset of "satellites" in English? Where a "moon" is a natural satellite?As I said: "It's a distinction I've seen made often, and one I find useful."


Would there also be terms for natural rainbows as opposed to artificial rainbows? Or natural clouds as distinct from artificial clouds?Less need, since the structure and origins are the same in the examples you propose. We seek verbal distinctions when an artificial object looks different or works differently from its natural counterpart.


Arthur C. Clarke wrote a book, published in 1957, titled "The Making of a Moon". Guess what kind of moon.

"The Brick Moon" by Edward Everett Hale, published as a serial in 'The Atlantic Monthly' in 1869, described the construction, launch, and life aboard an artificial Earth satellite.And I have an astronomy dictionary published in 1962 that describes an artificial satellite as a "man-made moon". Usage changes. Changes survive if they make a useful distinction.


While I generally use the terms exactly as you suggest, there is a long history of the word "moon" being used as a synonym for "satellite", whether natural or artificial.I do not deny that. Indeed, I confirm that (see above).


You seem to be reacting with some vigour to a pretty mild-mannered observation on my part. If I have caused annoyance, I apologize for that.

Grant Hutchison

Jeff Root
2007-Jul-09, 05:25 PM
You've got a problem with "mere"?
I'll work on a snappy comeback to that. None springs immediately
to mind.



You seem to be reacting with some vigour to a pretty mild-mannered
observation on my part. If I have caused annoyance, I apologize for that.
Annoyance. Hmmm. Perhaps. The "vigor" of my reaction is due to
two causes: I have an opinion on the subject, and I value your opinion.
So I may be annoyed that your opinion and mine would even consider
disagreeing with each other.

12:25 PM. Time to do some foodilization.

-- Jeff, in Minneapolis

dhd40
2007-Jul-09, 07:20 PM
(SNIP)
Anyway; I did a quick search, and there is an old thread with that exact question.
What is a moon? (http://www.bautforum.com/showthread.php?t=21505)

It gave me a chance to use the new Google search...Thanks.

Thanks for that link. I should have searched the BAUT fora before posting my question. But there doesn´t seem to be an "official" definition for "MOON"

NEOWatcher
2007-Jul-09, 07:26 PM
Thanks for that link. I should have searched the BAUT fora before posting my question. But there doesn´t seem to be an "official" definition for "MOON"
Exactly...that's one reason to send you to the thread. The discussion illustrates just how undefined it is.

Amber Robot
2007-Jul-09, 07:29 PM
Calling other planets satellites, "moons" is exactly like calling Venus, Mars, etc., "earths".

Or like calling extrasolar planetary systems "Solar Systems"....

oh wait, people do that! :mad:

dhd40
2007-Jul-09, 07:30 PM
(SNIP)
All the particles of Saturn's rings are moons, too.
(SNIP)

-- Jeff, in Minneapolis

May I kindly ask you to name the first trillion of them? :lol::):doh:

m1omg
2007-Jul-09, 07:33 PM
IMHO It does not matter if you call it moon, planet, asteroid...or a piece of rock, stone or -censored-

antoniseb
2007-Jul-09, 07:36 PM
I have a horrible feeling that we are opening up a nasty can of worms which will inevitably result in the IAU reclassifying the Moon as "Major Solar System Satellite 1969A".
No matter what happens, IAU will not say that any moon that most people already know the name of is not a moon... though frankly I don't think many school children can rattle off more than a dozen moon names. Name a body you think might 'suffer' Pluto's indignity.

Disinfo Agent
2007-Jul-09, 07:38 PM
Calling other planets satellites, "moons" is exactly like calling Venus, Mars, etc., "earths".No, it's like calling them "planets" -- which Earth does often get called, if you'll notice.

Moon, satellite, potayto, potahto... pedanteries. :rolleyes:

dhd40
2007-Jul-09, 07:54 PM
I expect that some definition could be made, perhaps something along the lines that a moon is a natural object with an orbit that has a barycenter that is inside an object classified as a planet(could perhaps also be extended to dwarf planets and so on). If the barycenter was outside, it would be a binary system.

I like that, nice idea, but ...


Of course, there would still be the problem of smallest size to be counted as a moon...

Indeed. And we will be faced with this problem as soon as Cassini has identified Saturn´s next 60 - 80 moons. Not really a big issue, but still amazing

Jeff Root
2007-Jul-09, 07:56 PM
All the particles of Saturn's rings are moons, too.
May I kindly ask you to name the first trillion of them? :lol::):doh:
Discoverers get to name the moons they discover, with approval
from the IAU. I haven't discovered any moons, so I can't name any.
Also, it seems unlikely that anyone would be able to identify and keep
track of that many individual ring particles over a long period of time,
even if they are tracked continuously. However, if they were tracked,
they would undoubtedly be given designations something like "SRM-1"
through "SRM-1000000000000".

May I unkindly ask you why you asked?

-- Jeff, in Minneapolis

Mister Earl
2007-Jul-09, 09:00 PM
Here's a good definition for moon: "An object is a moon if it rotates around another non-stellar body, and if the majority of the people you ask says it is so."

Van Rijn
2007-Jul-09, 11:44 PM
You seem to be reacting with some vigour to a pretty mild-mannered observation on my part. If I have caused annoyance, I apologize for that.

Grant Hutchison

I remember Jeff did the same in a previous discussion on the subject. For some reason, he seems to have a very specific and emotional position on the subject of satellites or moons.

Jens
2007-Jul-10, 04:43 AM
I have a horrible feeling that we are opening up a nasty can of worms which will inevitably result in the IAU reclassifying the Moon as "Major Solar System Satellite 1969A".

I've never heard of landing on an object as the date used for classification. Isn't it usually discovery? If so, that would make it:

Major Solar System Satellite 200,000BC A

(The date is a bit fuzzy, as presumably this should coincide with the emergence of homo sapiens.)

publius
2007-Jul-10, 05:10 AM
I think we should just adopt a definition of planets and moons in the same vein as a Supreme Court justice adopted toward obscenity. He said he couldn't define it exactly, but he knew it when he saw it.

And that's my defintion of "planet" and "moon", I know it when I see it.


-Richard

dhd40
2007-Jul-10, 09:00 AM
(SNIP)

May I unkindly ask you why you asked?

-- Jeff, in Minneapolis

It was meant to be a joke :(

Jeff Root
2007-Jul-10, 10:52 AM
It was meant to be a joke
The little dog laughed.

I ran away with the spoon.

-- Jeff, in Minneapolis

Jeff Root
2007-Jul-11, 07:30 AM
I feel that I poisoned the thread. I didn't wanna make anybody
frown -- even a cow.

-- Jeff, in Minneapolis

m1omg
2007-Jul-11, 06:38 PM
I've never heard of landing on an object as the date used for classification. Isn't it usually discovery? If so, that would make it:

Major Solar System Satellite 200,000BC A

(The date is a bit fuzzy, as presumably this should coincide with the emergence of homo sapiens.)

Why?Even the neandrthalis and hominids were able to recognise Moon.

Jens
2007-Jul-12, 07:58 AM
Why?Even the neandrthalis and hominids were able to recognise Moon.

Well, it becomes somewhat philosophical, doesn't it? What if we ask who discovered the New World? When I was a child, American children were often taught that it was Columbus. Now, discounting even theories about pre-Columbus voyagers, it is quite clear that the Native Americans "discovered" it quite a bit earlier. And now, if we take your assertion, then maybe other hominids were in the New World earlier. But wait. The dinosaurs clearly discovered it much earlier. . . My solution, which you took exception to, was to define "discovery" as "the discovery of something by our own species."

dhd40
2007-Jul-24, 07:11 PM
I feel that I poisoned the thread. I didn't wanna make anybody
frown -- even a cow.

-- Jeff, in Minneapolis

Sorry for a late reply, I was away for a while. I don´t think that you poisened the thread. But, honestly, I don´t understand your post # 34. I have some idea about it (some kind of joke, as well?). Don´t worry, that´s not your problem.

I still wonder how astronomy/astrophysics will define the limit (weight, size, etc) for a celestial body circling a planet (or a comet, or an asteroid, etc.) to be called a moon. Ida´s moon Dactyl, approx. 1.4 km diameter, is still called a moon.

Scopeman
2007-Jul-24, 10:39 PM
I`ve heard people saying Moon is a planet. Silly move, ha:) Well but planets are usually solid so the Moon is. How strange.

Jeff Root
2007-Jul-24, 11:50 PM
Sorry for a late reply, I was away for a while. I don´t think that you
poisened the thread. But, honestly, I don´t understand your post # 34.
I have some idea about it (some kind of joke, as well?).
I was attempting a light-hearted reply that would acknowledge
your post while weasling out of addressing any specifics.

Hey diddle diddle,
The cat and the fiddle,
The cow jumped over the moon,
The little dog laughed to see such sport,
And the dish ran away with the spoon.



I still wonder how astronomy/astrophysics will define the limit
(weight, size, etc) for a celestial body circling a planet (or a comet,
or an asteroid, etc.) to be called a moon. Ida´s moon Dactyl,
approx. 1.4 km diameter, is still called a moon.
I don't see any need for a limit. A limit based on size or mass
seems especially pointless.

-- Jeff, in Minneapolis

dhd40
2007-Jul-26, 09:01 PM
(snip)
Hey diddle diddle,
The cat and the fiddle,
The cow jumped over the moon,
The little dog laughed to see such sport,
And the dish ran away with the spoon.


Nice, especially the idea of my avatar jumping over the moon. What´s the name of the poet, or the title of the poem?


I don't see any need for a limit. A limit based on size or mass seems especially pointless.

A limit based on what would be appropiate?
As I mentioned before, it´s not a big issue. But I still wonder when they will start thinking about some kind of definition in order to avoid looking for new (ancient) gods/goddesses

mugaliens
2007-Jul-26, 09:29 PM
:DThe mismatch between the count of Saturn's discovered moons (63 at present) and named moons (48 at present) is because it takes time for the IAU to approve new names, so at any one time there are usually a number of nameless moons indentified by numbers describing their discovery circumstances.

I don't know if the cut-off between "moon" and "ring particle" has ever been given an official value; I suspect not.
("Clearing its orbital neighbourhood" might be involved :D: moons within the ring system create gaps by their gravitational interactions with the ring particles.)

Grant Hutchison

You bring up a terrific point. Let's propose a limit: 10% of the planetary mass. Anything less than that is "space dust." Naturally, Mars would loose it's moons under this, so the value may be adjusted. I dunno - 1%?

Jeff Root
2007-Jul-27, 01:16 AM
Hey diddle diddle,
The cat and the fiddle,
The cow jumped over the moon,
The little dog laughed to see such sport,
And the dish ran away with the spoon.
Nice, especially the idea of my avatar jumping over the moon.
What´s the name of the poet, or the title of the poem?
Unknown author. The first line is used as the title in the
Wikipedia article (Again, anything and everything can be found
on Wikipedia, now). This English nursery rhyme is quite familiar
in America. Note the astronomy interpretation!

http://en.wikipedia.org/wiki/Hey_Diddle_Diddle




I don't see any need for a limit. A limit based on size or mass seems
especially pointless.
A limit based on what would be appropiate?
How about identifiability? If you can locate it and keep track
of it without loosing it, you call it a moon. Sound good?



As I mentioned before, it´s not a big issue. But I still wonder when
they will start thinking about some kind of definition in order to
avoid looking for new (ancient) gods/goddesses
I don't know what gods have to do with anything.
I think they've been out of the loop for some time.

-- Jeff, in Minneapolis

dhd40
2007-Jul-27, 11:30 AM
Unknown author. (SNIP) This English nursery rhyme is quite familiar
in America. Note the astronomy interpretation! (SNIP)

Oh, thanks!


How about identifiability? If you can locate it and keep track
of it without loosing it, you call it a moon. Sound good?

At a first glance:Yes. But then what about all the debris in our Earth´s space-environment? I´ve no idea how small the smallest of it is which can be tracked without loosing it. My guess would still be that there must quite a few. So, Earth is the planet with a moon-number-record in our solar system?


I don't know what gods have to do with anything.
I think they've been out of the loop for some time.

-- Jeff, in Minneapolis

How about Mars? Roman god of war.

loglo
2007-Jul-29, 05:40 AM
I have a recent text book which says, from memory, that the IAU recommends dropping the "The" from Sun and Moon (and Earth I think), as no other solar system object is called "the" anything. This would suggest that the IAU consider Moon to be the one orbiting Earth and everything else orbiting any planet is a satellite.

astromark
2007-Jul-29, 06:35 AM
This subject does get confusing... we understand Dwarf Planet. Natural satellite. Large Moon. and on and on we go... BUT! Titan is classified as a moon as it orbits a planet. While Mercury is smaller and still a Planet as it orbits a star. Those smaller objects that do not have sufficient mass to pull themselves into spheres should perhaps be natural satellites and reserve the title moon for the Moons... and add the word Lunar when we talk of Earths Moon. Just an unsupported opinion...sorry.
Once again we creep of topic and actually become a language lesson. Still of interest tho because the use of these terms is what makes astronomy,astronomy.

mugaliens
2007-Jul-29, 04:49 PM
Ok, no takers, so let's try this again: Within one order of magnitude of the planetary mass.

There - that's better, nice round figure, and will still excluse the debris in those pesky rings.

neilzero
2007-Jul-29, 05:34 PM
Within one order of magnitude of mass would exclude all or most of what we call moons. How about: It is not a moon unless the primary has less than one million times the mass of the satellite? Even that would exclude some of the least massive moons of Jupiter and Saturn, but it would include the 2 ton moon of a million ton asteroid or comet. Neil

dgavin
2007-Jul-29, 05:49 PM
I expect that some definition could be made, perhaps something along the lines that a moon is a natural object with an orbit that has a barycenter that is inside an object classified as a planet(could perhaps also be extended to dwarf planets and so on). If the barycenter was outside, it would be a binary system.

Of course, there would still be the problem of smallest size to be counted as a moon...

Actually a Double Planet using the Bary Center consept was in the first IAU proposal that was rejected. It's an unknown why it was left out of the second definition that was accepted, as the IAU hasn't specified why it wasn't carried forward.

01101001
2007-Jul-29, 06:12 PM
I have a recent text book which says, from memory, that the IAU recommends dropping the "The" from Sun and Moon (and Earth I think), as no other solar system object is called "the" anything.

I really doubt that's the IAU's position. If the IAU recommends dropping the "The", why don't they take their own advice?

Google site:iau.org "the sun" (http://www.google.com/search?num=100&hl=en&safe=off&rls=GGLG%2CGGLG%3A2005-42%2CGGLG%3Aen&q=site%3Aiau.org+%22the+sun%22) example results:


IAU Website: iau0603(1) A "planet"1 is a celestial body that (a) is in orbit around the Sun, ... (3) All other objects3 except satellites orbiting the Sun shall be referred to ...
www.iau.org/iau0603.414.0.html - 25k - Cached - Similar pages

IAU Website: Q&A2A: Modern science provides much more knowledge than the simple fact that objects orbiting the Sun appear to move with respect to the background of fixed ...
www.iau.org/Q_A2.415.0.html - 25k - Cached - Similar pages

[PDF] IAU Resolutions 5 and 6File Format: PDF/Adobe Acrobat - View as HTML
except satellites, orbiting the Sun shall be referred to. collectively as "Small Solar System Bodies". 1. The eight planets are: Mercury, Venus, Earth, ...
www.iau.org/Resolutions_5-6.398.0.html - Similar pages

Google site:iau.org "the earth" (http://www.google.com/search?num=100&hl=en&safe=off&rls=GGLG%2CGGLG%3A2005-42%2CGGLG%3Aen&q=site%3Aiau.org+%22the+earth%22) example results:


IAU Website: NEAR EARTH OBJECTSFrom time to time, we have all seen stories in the Press about Near Earth Objects that are about to hit the Earth on some date in the not-too-distant future ...
www.iau.org/NEAR_EARTH_OBJECTS.306.0.html - 18k - Cached - Similar pages

[PDF] IAU 2006 Resolution 1 English version Adoption of the P03 ...File Format: PDF/Adobe Acrobat - View as HTML
motion of the Earth’s equator, making the terms lunisolar precession and planetary ... tum vector of the Earth-Moon barycenter in the Barycentric Celestial ...
www.iau.org/Resolution_1.400.0.html - Similar pages

[DOC] Planet definitionFile Format: Microsoft Word - View as HTML
Q: The Earth’s moon is spherical. Is the Moon now eligible to be called a “planet” ... The Moon is a satellite of the Earth. The reason the Moon is called a ...
iau.org/fileadmin/content/news/iau0601/iau0601_Q_A.doc - Similar pages

Google site:iau.org "the moon" (http://www.google.com/search?num=100&hl=en&safe=off&rls=GGLG%2CGGLG%3A2005-42%2CGGLG%3Aen&q=site%3Aiau.org+%22the+moon%22) example results:


[DOC] Planet definitionFile Format: Microsoft Word - View as HTML
Is the Moon now eligible to be called a “planet”? A: No. The Moon is a satellite of the Earth. The reason the Moon is called a “satellite” instead of a ...
iau.org/fileadmin/content/news/iau0601/iau0601_Q_A.doc - Similar pages

IAU Website: iau0601_Q_AIs the Moon now eligible to be called a “planet”? ... The reason the Moon is called a “satellite” instead of a “planet” is because the common centre of ...
www.iau.org/iau0601_Q_A.435.0.html - 49k - Cached - Similar pages

IAU Website: BUYING STAR NAMESQ: But what about the companies that sell pieces of territory on the Moon and other planets? Those are within reach, we know, so surely I own the piece that ...
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Maybe the IAU is too slow to react to their own advice? Let's check something sure to be up-to-date:

Wikipedia: Astronomical naming conventions (http://en.wikipedia.org/wiki/Astronomical_naming_conventions)


The star nearest to Earth, our Sun, is typically referred to simply as "the Sun"[...]
Our own planet is usually named the Earth[...]
The Earth's moon is simply known as the Moon[...]

Jeff Root
2007-Jul-29, 10:56 PM
In my writing here and on my web pages I refer to the Earth, Moon,
and Sun with or without the definite article as feels right for the
sentence. But for the past 20 or more years it has been my policy
to capitalize "Earth" when referring to our planet by name, capitalize
"Moon" when referring to our moon by name, and capitalize "Sun"
when referring to our star by name. I also use the name "Luna" for
the Moon, but have not cared to use "Sol" as an alternative name
for the Sun because it is less familiar and is confusible with "sol", a
term for the length of a day on planets other than Earth.

-- Jeff, in Minneapolis

Maksutov
2007-Jul-29, 11:39 PM
moon v. intr.

Slang To expose one's buttocks in public as a prank or disrespectful gesture.We folks climbing the last scramble up Mt. Washington by the Gulfside Trail (which paralleled the cog railway for a bit) started a tradition back in the late 1960s. When a trainload of tourists would approach the trail it became traditional for us hikers to moon the cog. Somewhere a tourist probably still has a photo of some folks from Connecticut completely covered by huge backpacks and other hiking equipment, except for one critical area.

Meanwhile the IAU is still completely deficient in their current planet definition and proposed moon definition since they have specified no tolerance whatsoever on sphericity (http://en.wikipedia.org/wiki/Sphericity), other than a vague, qualitative bit of wording, which is, in science, useless.

mugaliens
2007-Jul-30, 02:18 AM
Well, it becomes somewhat philosophical, doesn't it? What if we ask who discovered the New World? When I was a child, American children were often taught that it was Columbus. Now, discounting even theories about pre-Columbus voyagers, it is quite clear that the Native Americans "discovered" it quite a bit earlier. And now, if we take your assertion, then maybe other hominids were in the New World earlier. But wait. The dinosaurs clearly discovered it much earlier. . . My solution, which you took exception to, was to define "discovery" as "the discovery of something by our own species."

It's difficult to discount the Viking ruins...

When I went to school, I was taught 500 years ago, Columbus, et al, too. Then Thor's Kon Tiki raised some doubts, giving credence that it could have been a thousand years before. Next, common sense said native Americans are our species (land bridge migrations of several thousand years ago, to tens of thousands of years). Genetic discoveries reveal Oceanic (sailing) influence with arrival times ranging from 30,000 to 50,000 years ago.

As for keeping it within the species, do we know for certain that ancestors from, say, 100,000 years ago weren't able to sail the Southern oceans, and were they of our same species, or, more to the point, would we be able to breed with them if they were here today? (or possibly, would we want to?)

dhd40
2007-Jul-30, 07:44 PM
This subject does get confusing... (SNIP=)

Eureka, it does. Do Trojans orbit their planet (Mars, Jupiter, Saturn)? Not in a common sense. BUT ... it depends on the chosen frame of reference (epicycles!). What about Eureka (Martian Trojan) in a Mars-centered, rotating frame? For marsbound observers it should behave like a moon? (If bright enough to be seen by the green little martians)

grant hutchison
2007-Jul-30, 07:52 PM
What about Eureka (Martian Trojan) in a Mars-centered, rotating frame? For marsbound observers it should behave like a moon?More like the Sun. It would go around the sky once per Martian year, staying sixty degrees (on average) away from the Sun.

Grant Hutchison

tony873004
2007-Jul-30, 08:33 PM
...What about Eureka (Martian Trojan) in a Mars-centered, rotating frame? For marsbound observers it should behave like a moon?...

In a rotating frame, it is stationary with respect to Mars.
animation (1.4Mb):
http://www.orbitsimulator.com/gravity/marstrojans.GIF
Red=Mars, Maroon=Eureka. Also included are two other Mars trojans (a new one was discovered last week, but it is not in this animation), and a few asteroids that are almost in 1:1 resonances but don't qualify as trojans.

In a non-rotating frame of reference, centered on Mars, Eureka appears to travel around Mars (as do the Sun, Mercury, Venus, and Earth).

** edit: I replaced the image with a link at Jeff's suggestion, as it's a bit large for dial-up users.

01101001
2007-Jul-30, 08:54 PM
In a rotating frame[...]

Yes... master... Anything you say... master...

Wha... Hey, you almost got me hyp-mo-tized watching your spinny thing!

dhd40
2007-Jul-31, 04:44 PM
In a rotating frame, it is stationary with respect to Mars. (SNIP)


In a non-rotating frame of reference, centered on Mars, Eureka appears to travel around Mars (as do the Sun, Mercury, Venus, and Earth).

I´m somewhat confused concerning rotating/non-rotating frame of reference. My thinking was: Because the duration of a Martian day is close to an Earth-day an observer on Mars should see Eureka-rises and Eureka-sets in a similar way as we see Sunrises and Sunsets. Oh, now I see: as do the sun, ...
Thanks

Jeff Root
2007-Jul-31, 08:16 PM
Tony,

Could you just link to that animation instead of putting it on the page?
That is a bit overwhelming for my slow computer and slow modem
connection. Not nearly as bad as many web pages, but enough to
meow about.

It was good to get a look at it for a time. Thank you!

-- Jeff, in Minneapolis

tony873004
2007-Jul-31, 08:42 PM
Sorry, Jeff. With dsl I forget how large these files actually are. You're not going to like the one I just posted in the "orbiting planets" thread. (you may like it, but you won't like the dl time.) ** edit: it's only 1/3 the size of the one in this thread, so I'll leave it. But I'll edit the one in this thread to a link.