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Orbital Geometry, re: The Moons of Az
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Albatros
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PostPosted: Thu Feb 02, 2006 6:04 pm    Post subject: Orbital Geometry, re: The Moons of Az Reply with quote

This thread is for the straightforward discussion of exactly what the moons are doing in The Murloc is Lonely - on a purely physical level. I assume that orbital geometry works the same in Az as it does here, and that the moons are in fact reflecting the light of the sun rather than glowing on their own.

ASSUMING that I did my geometry correctly, the whole thing with what moon is where and which is waxing and waning how is actually really straightforward and non-magical. See if you guys can decipher it.

If I screwed it up, hopefully this thread will illumitate it for me. no pun intended.

Math/space geeks - be the first to figure it out! because horse sure hasn't yet...
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Saranus



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PostPosted: Fri Feb 03, 2006 12:30 am    Post subject: Reply with quote

ok, lets list what we know:

1. The white moon (which is also the original moon) has never waxed or waned. It's only ever been full.

2. I don't know if it's just now, post-Hannathras-messing-with-it, has always been, or if it was just for the day that horse was looking at it, but the white moon doesn't move. It stayed in the northeast the whole time. I don't know if it's important to the story, or if you can tell us now, but has the moon always been stationary or is that a new thing, or are we not allowed to know yet?Wink

3. The new, blue moon rose in the east like our moon. Didn't say if it was full or not. Don't know if that's important. Anyway, it seems to me like blue is behaving like our moon. We don't know if blue waxes and wanes (I don't think. I'm assuming its full right now).

4. So now we have 2. One that rises and sets like normal and is weird because of its color. Another that looks the normal white but sits in one place and goes through its phases in a very short period of time. (Of course, I'm assuming here that the white moon has never moved and the only peculiar thing about it is the whole waxing/waning thin

So to determine what's up with white moon, I have to ask what is moving so fast that it makes it wax and wane in a matter of hours? Two possibilities: Azeroth the planet or the blue moon. Since azeroth wasn't bombarded with demon fire I'm assuming that the blue moon is casting the shadow. And also, since I'm assuming that the white moon still doesn't move, Azeroth couldn't suddenly be casting shadows on it since the dynamic between those two hasn't changed. Basically the only new thing is the blue moon. I have to wonder though, what was it doing the whole time behind the white moon? Following it exactly from behind so no one could see it?

I kind of jumped around there. Can anyone else make sense of this? Razz
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Heloly



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PostPosted: Fri Feb 03, 2006 7:58 am    Post subject: Reply with quote

Saranus wrote:
ok, lets list what we know:

1. The white moon (which is also the original moon) has never waxed or waned. It's only ever been full.



But it did wax and wane.... It went through a full moon cycle in a day.
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Saranus



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PostPosted: Fri Feb 03, 2006 3:24 pm    Post subject: Reply with quote

what I meant was, before the cataclysm it never moved or went through cycles. At least thats the conclusion I came to. Did it go through the phases before this?
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Saranus



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PostPosted: Fri Feb 03, 2006 3:27 pm    Post subject: Reply with quote

Oh! I just thought of something! Maybe the fact that the blue moon has been gone all this time has something to do with the fact that the Night Elves are gone. You know, with all their druid/priestess connections to the moon and whatnot (Elune?).
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Albatros
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PostPosted: Fri Feb 03, 2006 4:55 pm    Post subject: Reply with quote

Saranus wrote:
ok, lets list what we know:

1. The white moon (which is also the original moon) has never waxed or waned. It's only ever been full. [before the cataclysm]


Correct. See chapter 6. (Back then, I was just making fun of WoW for having an always-full moon.)

Saranus wrote:
2. I don't know if it's just now, post-Hannathras-messing-with-it, has always been, or if it was just for the day that horse was looking at it, but the white moon doesn't move. It stayed in the northeast the whole time. I don't know if it's important to the story, or if you can tell us now, but has the moon always been stationary or is that a new thing, or are we not allowed to know yet?Wink


The white moon rose often in Part One (e.g. chapter 16) - and always just as the sun set, which you'd expect from an always-full moon, right? If you can picture how this works, the rest should come together fairly easily. Hint: the lunar orbit required to have an always-full moon is the first thing I came up with in all this.

Saranus wrote:
3. The new, blue moon rose in the east like our moon. Didn't say if it was full or not. Don't know if that's important. Anyway, it seems to me like blue is behaving like our moon. We don't know if blue waxes and wanes (I don't think. I'm assuming its full right now).


The blue moon is indeed full, and that is important to the present question. (less so to the story at large, i.e. no more important than the fact that the white moon was always full before.)

Saranus wrote:
4. So now we have 2. One that rises and sets like normal and is weird because of its color. Another that looks the normal white but sits in one place and goes through its phases in a very short period of time. (Of course, I'm assuming here that the white moon has never moved and the only peculiar thing about it is the whole waxing/waning thin

So to determine what's up with white moon, I have to ask what is moving so fast that it makes it wax and wane in a matter of hours? Two possibilities: Azeroth the planet or the blue moon.


You're thinking too hard. What controls which face of the moon is lit? Here's a hint, since I didn't make it entirely clear in the chapter: the white moon is now going through its entire set of phases once per day. (you got it heloly)

Saranus wrote:
Basically the only new thing is the blue moon. I have to wonder though, what was it doing the whole time behind the white moon? Following it exactly from behind so no one could see it?


hmm. Wink
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Cangjku



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PostPosted: Fri Feb 03, 2006 9:56 pm    Post subject: Reply with quote

The only possible orbit I can think of t hat would allow a moon to stay permenantly full is one in which the moon didn't move at all and was situated on the far side of Az from the sun. Now in our reality this wouldn't work, a stationary moon would fall towards earth rather fast assumming it was at the same distance as our moon is from the earth.

However if a planetary body were located at the appropriate lagrange point it wouldn't move at all and wouldn't you know one of the 5 lagrange points that exist around all orbiting bodies is located on the far side of a planet from the sun. This particular lagrange point is unstable, stuff can fall out of it, but would be the only place a moon could exist and not go throgh phases of any type. Of course this doen't explain why the moon suddenly started going through phases. Even if the moon simply started to rotate on its axis it woulldn't go through phases you would just see a different side of the moon. It could start going through phases only if it started to orbit and the only way you would have daily or hourly phases would be if it were orbiting really really fast. At least I can't think of a way. That mystery will take some time to solve.

As for the blue moon well since any two orbiting bodies will have 5 lagrange points the blue moon most probably was stuck at the same lagrange point of the white moon, that the white moon was at with Az. When the white moon was bombarded with fire balls it started to move but the blue moon didn't. This would cause the blue moon to lelave its orbit though.

Sigh, be happy this is Fantasy Albatros, because a real astronamer would likely have a field day with it.

If you are curiouse about Lagrange points, here is a link that should help.

http://physics.montana.edu/faculty/cornish/lagrange.html
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Albatros
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PostPosted: Fri Feb 03, 2006 11:42 pm    Post subject: Reply with quote

Cangjku wrote:
The only possible orbit I can think of t hat would allow a moon to stay permenantly full is one in which the moon didn't move at all and was situated on the far side of Az from the sun.


You've basically got it, all except the precise length of time it takes the white moon to orbit Az now... as for the blue moon leaving its orbit, you'll notice that it got hit with some fireballs too.

I didn't know that Lagrange points were unstable - which I should have, of course. anyway, that just means that Hannathras's fireball calculations had to be sort of... unrealistically precise. bum!
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Gan Xingba



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PostPosted: Sun Feb 05, 2006 1:15 pm    Post subject: Reply with quote

Oh? Non-magical, huh? Damn, and here I was thinking this had something to do with Elune (the godess of the moon that the Night Elves worship). Oh well, physics is good too.
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Albatros
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PostPosted: Sun Feb 05, 2006 1:33 pm    Post subject: Reply with quote

Gan Xingba wrote:
Oh? Non-magical, huh? Damn, and here I was thinking this had something to do with Elune (the godess of the moon that the Night Elves worship). Oh well, physics is good too.


no see, that's the point of this thread - there is magical stuff going on, big scary high-concept magical stuff - but it's exhibiting itself in very straightforward mundane ways. In my story, the moons go around Az and reflect the sun's light, and and Az goes around the sun, and that all makes sense. I wanted to make this thread to help make clear where the magic was, and where it wasn't.
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Amaunator



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PostPosted: Sun Feb 05, 2006 1:37 pm    Post subject: Reply with quote

This is fan fiction damnit Smile, no point in taking it any further than need be Wink. Nice touch though Wink.
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Egann



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PostPosted: Tue Mar 21, 2006 11:42 am    Post subject: Reply with quote

Hey, it's me, the ever-present lazy slacker who wouldn't register. Only now I have because I felt bad about hiding behind anonymity. Now I'm just hiding behind a made-up name. Smile

Anyway, if you'll excuse my resurrecting this thread...

Albatros wrote:
You're thinking too hard. What controls which face of the moon is lit? Here's a hint, since I didn't make it entirely clear in the chapter: the white moon is now going through its entire set of phases once per day. (you got it heloly)


I think I have a problem with this. For the moon to go through all its phases in one day, it would have to orbit the planet once per day. However, this would be (by definition) a geostationary orbit; the moon would always be above the same spot on the planet. It wouldn't move through the sky.

I suppose one could imagine that the moon was orbiting in the opposite direction of the planet's rotation. The orbit would be the same as a geostationary orbit, but the moon would appear to move really fast through the sky (two crossings per day). I think the only example of such a retrograde orbit in our solar system is Neptune's moon Triton (which has led to the belief that it was captured into orbit rather than fromed with or from the planet)...so I'll give you that one. Smile

Interestingly (although not surprsingly if you work it out), the altitude of an object in geostationary orbit depends on the mass of the planet, but not on the mass of the satellite. For the earth, this altitude is a bit less than 36000 km above sea level, corresponding to an orbital radius of about 42000 km. By way of comparison, the earth's moon has an orbital radius nearly 10 times that large.

According to the interesting calculations presented on the page Cangjku linked, the Lagrange point L2 is about 1.5 million miles (~2.4 million km) from the earth. If we assume (and I know, it's a big assumption) that our fantasy world has roughly similar planetary and lunar masses, the moon would have to drop from a 2.4 million km orbit to a 42000 km orbit. Of course, anything is possible when you bring undead and demons and magic into the equation, but wouldn't the moon have suddenly appeared much larger in the sky?

Fortunately, even a 42000 km orbit is well outside the Roche limit--inside which tidal forces would tear the satellite apart, eventually forming a planetary ring.

I know, I know, I'm neglecting the blue moon, and I'm assuming masses, densities, and sizes roughly similar to the sun-earth-moon system. And of course the magic. /sigh.... Now I'm the one thinking too hard. Sorry. Smile
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Exodus



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PostPosted: Tue Mar 21, 2006 10:57 pm    Post subject: Reply with quote

Wow, great post even though I didn't read it all. It hurt my brain.
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Albatros
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PostPosted: Wed Mar 22, 2006 5:37 am    Post subject: Reply with quote

Egann wrote:
I think I have a problem with this. For the moon to go through all its phases in one day, it would have to orbit the planet once per day. However, this would be (by definition) a geostationary orbit; the moon would always be above the same spot on the planet. It wouldn't move through the sky.


you got it, dude. (welcome on board finally Smile )

Egann wrote:
Interestingly (although not surprsingly if you work it out), the altitude of an object in geostationary orbit depends on the mass of the planet, but not on the mass of the satellite. For the earth, this altitude is a bit less than 36000 km above sea level, corresponding to an orbital radius of about 42000 km. By way of comparison, the earth's moon has an orbital radius nearly 10 times that large.

According to the interesting calculations presented on the page Cangjku linked, the Lagrange point L2 is about 1.5 million miles (~2.4 million km) from the earth. If we assume (and I know, it's a big assumption) that our fantasy world has roughly similar planetary and lunar masses, the moon would have to drop from a 2.4 million km orbit to a 42000 km orbit. Of course, anything is possible when you bring undead and demons and magic into the equation, but wouldn't the moon have suddenly appeared much larger in the sky?

Fortunately, even a 42000 km orbit is well outside the Roche limit--inside which tidal forces would tear the satellite apart, eventually forming a planetary ring.

I know, I know, I'm neglecting the blue moon, and I'm assuming masses, densities, and sizes roughly similar to the sun-earth-moon system. And of course the magic. /sigh.... Now I'm the one thinking too hard. Sorry. Smile


Noooo kidding. thanks for the numbers, dude. I made the whole shebang up in a moment with no actual research - let this be a lesson to anyone who writes things for audiences (lots of people, or one, say, professor) who just might go and do the math.

If what you're saying is correct, then I'll head back at some point and retroactively add a bit at some point about the suddenly increased size of the moon. Maybe something about tides rising higher and eratically too (there's still room for that - we haven't been by the ocean yet for any good period of time). using facts has fun consequences! Razz
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Ulkarr



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PostPosted: Wed Mar 22, 2006 6:53 am    Post subject: Reply with quote

You could get away without saying anything about the size because you did say that a huge chunk of it got blasted away so the effect of it 'getting larger'is balanceed by its reduction in true size. But the tidal effect would be an excelent writing point. Just my 2 cents..... well more like 1..... oh well.
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