(C&C) Q&A Thread - Quick questions go here

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Re: (C&C) Q&A Thread - Quick questions go here

Post by Ahzoh » Tue 17 Jul 2018, 04:06

Axiem wrote:
Tue 17 Jul 2018, 03:32
Ultimately, the only real way to answer that question is to plug the numbers into a simulator and set it to run and see what happens.
Well I put them in a gravity simulator but all the moons I put in it start flinging off the planet within less than a year, even if I give them stable orbital resonance frequencies. Which is why I'm wondering if what I'm proposing is too impossible.

And for the record, the planet is basically earth for all intents and purposes and likewise for its sun. The moons are very close to our moon in size and they have to be in order to have the desired rotation periods and naturalistic densities for non-icy moons.
sangi39 wrote:
Tue 17 Jul 2018, 03:54
you might just have to lower the mass of the larger moon.
The problem is that by changing the mass, it changes the rotational period or the density of the moon drastically.
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Re: (C&C) Q&A Thread - Quick questions go here

Post by sangi39 » Tue 17 Jul 2018, 04:11

Ahzoh wrote:
Tue 17 Jul 2018, 04:06

sangi39 wrote:
Tue 17 Jul 2018, 03:54
you might just have to lower the mass of the larger moon.
The problem is that by changing the mass, it changes the rotational period or the density of the moon drastically.
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Re: (C&C) Q&A Thread - Quick questions go here

Post by Salmoneus » Tue 17 Jul 2018, 12:46

Well, basic googling shows that yes, 1:3:6 resonances are possible, but looking at the articles they seem to mean the opposite way around (i.e. those numbers being frequencies rather than periods). That would mean, in terms of periods, 1:2:6. That is, the inner moons are an octave apart, while the outer moon is a perfect twelfth further out. Intuitively, this seems to make sense: harmonies greater than an octave seem rare in space, perhaps because the bodies would just be too far apart; in 1:3:6, the moon at the twelfth is pulling the octave moon further out, and it's already a long way from the gravity of the first. Whereas in 1:2:6 (in terms of periods), the inner two moons are close, and can both collaborate in keeping the twelfth in line.
[plus, I don't know about you, but the perfect twelfth doesn't actually sound that great. But maybe that's cultural conditioning.]

So, I don't know. I'd guess you could get the resonance you want by having the innermost moon significantly larger, or something? In the '1:3:6' resonance a paper I found discusses, btw (by which I think they mean 1:2:6 in your terms), apparently inclination of the moons increases rapidly to create a 3D system, not a simple planar alignment. Eccentricities also increase, and this causes tidal heating. In our system, Miranda is believed to have escaped from a 1:3 resonance, but to have ended up with a ridiculous inclination as a result.


However, I don't think any of that matters here. Because you've got an earth-size planet and three moon-size moons, so you can probably wave plausibility goodbye from the start. The moon is already about as large as the earth can handle - triple the size of the moon and I think you've got problems! But more significantly, you're into a big n-body problem there. Without a really massive planet, your moons are going to collapse into unpredictable chaotic orbits and at least some of them are going to go flying off.

For comparison here: the largest Jovian moon is twice the size of Luna. But Jupiter is over 300 times larger than Earth. You can get Jovian-style moon systems in the Jovian system because Jupiter's in the order of 30,000 times larger than even the largest of its moons; whereas your planet would only be around 100 times larger than your moons (30 times larger than all your moons together). And for reference: the Sun is around 1,000 times larger than Jupiter - but even that's enough to put the barycenter of the system outside the sun when the planet line up in certain ways. Your moons, if they could stay, which I don't think they can, would really be yanking your planet around, about a centre way outside itself! It wouldn't so much be a planet and moons, as a quaternary planet system!
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Re: (C&C) Q&A Thread - Quick questions go here

Post by Ahzoh » Tue 17 Jul 2018, 13:14

Salmoneus wrote:
Tue 17 Jul 2018, 12:46
Well, basic googling shows that yes, 1:3:6 resonances are possible, but looking at the articles they seem to mean the opposite way around (i.e. those numbers being frequencies rather than periods). That would mean, in terms of periods, 1:2:6. That is, the inner moons are an octave apart, while the outer moon is a perfect twelfth further out. Intuitively, this seems to make sense: harmonies greater than an octave seem rare in space, perhaps because the bodies would just be too far apart; in 1:3:6, the moon at the twelfth is pulling the octave moon further out, and it's already a long way from the gravity of the first. Whereas in 1:2:6 (in terms of periods), the inner two moons are close, and can both collaborate in keeping the twelfth in line.
[plus, I don't know about you, but the perfect twelfth doesn't actually sound that great. But maybe that's cultural conditioning.]

So, I don't know. I'd guess you could get the resonance you want by having the innermost moon significantly larger, or something? In the '1:3:6' resonance a paper I found discusses, btw (by which I think they mean 1:2:6 in your terms), apparently inclination of the moons increases rapidly to create a 3D system, not a simple planar alignment. Eccentricities also increase, and this causes tidal heating. In our system, Miranda is believed to have escaped from a 1:3 resonance, but to have ended up with a ridiculous inclination as a result.


However, I don't think any of that matters here. Because you've got an earth-size planet and three moon-size moons, so you can probably wave plausibility goodbye from the start. The moon is already about as large as the earth can handle - triple the size of the moon and I think you've got problems! But more significantly, you're into a big n-body problem there. Without a really massive planet, your moons are going to collapse into unpredictable chaotic orbits and at least some of them are going to go flying off.

For comparison here: the largest Jovian moon is twice the size of Luna. But Jupiter is over 300 times larger than Earth. You can get Jovian-style moon systems in the Jovian system because Jupiter's in the order of 30,000 times larger than even the largest of its moons; whereas your planet would only be around 100 times larger than your moons (30 times larger than all your moons together). And for reference: the Sun is around 1,000 times larger than Jupiter - but even that's enough to put the barycenter of the system outside the sun when the planet line up in certain ways. Your moons, if they could stay, which I don't think they can, would really be yanking your planet around, about a centre way outside itself! It wouldn't so much be a planet and moons, as a quaternary planet system!
Well maybe they are not all moon-sized exactly; the innermost could be about 15-20 arcminutes (Luna is about 30), the second could be 20-25, and the outermost could be 25-30.
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Re: (C&C) Q&A Thread - Quick questions go here

Post by Axiem » Tue 17 Jul 2018, 16:51

Ahzoh wrote:
Tue 17 Jul 2018, 04:06
Well I put them in a gravity simulator but all the moons I put in it start flinging off the planet within less than a year, even if I give them stable orbital resonance frequencies. Which is why I'm wondering if what I'm proposing is too impossible.
If the simulator throws them out, then yeah, you're probably in the realm of the impossible.
The moons are very close to our moon in size
Assuming you're including both volume and mass (therefore density) in that "size", then yes, this is impossible. You're dealing with objects that are massive enough to interfere with each other's orbits significantly, especially in such small distances.
sangi39 wrote:
Tue 17 Jul 2018, 03:54
The problem is that by changing the mass, it changes the rotational period or the density of the moon drastically.
Mass has nothing to do with rotation period, unless your moons are tidally locked, and saying "rotational period" instead of "orbital period" is confusing. Are your moons tidally locked?
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Re: (C&C) Q&A Thread - Quick questions go here

Post by Axiem » Tue 17 Jul 2018, 16:54

Ahzoh wrote:
Tue 17 Jul 2018, 13:14
Well maybe they are not all moon-sized exactly; the innermost could be about 15-20 arcminutes (Luna is about 30), the second could be 20-25, and the outermost could be 25-30.
By "size", are you referring to the angular diameter from the planet's surface, then? I thought you were talking about the actual like, volume/mass of the body.

A thing to keep in mind: orbital resonances refer to the orbital period, which is going to be different from the synodic period. So, if you're wanting there to be a clear resonance of the orbits from the perspective of someone on the planet, you'll need to start with the synodic period and use that (with the solar day of the planet) to calculate the orbital period.
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Re: (C&C) Q&A Thread - Quick questions go here

Post by Ahzoh » Tue 17 Jul 2018, 17:14

When I said the planet was earth for all intents and purposes, that also means the time it takes for the planet to travel around the sun is also the exact same.
Mass has nothing to do with rotation period, unless your moons are tidally locked, and saying "rotational period" instead of "orbital period" is confusing. Are your moons tidally locked?
They're tidally locked, I'm talking about the time it takes for them to rotate around the earth, which really is dependent on mass.
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Re: (C&C) Q&A Thread - Quick questions go here

Post by eldin raigmore » Tue 17 Jul 2018, 17:22

Ahzoh wrote:
Tue 17 Jul 2018, 17:14
Mass has nothing to do with rotation period, unless your moons are tidally locked, and saying "rotational period" instead of "orbital period" is confusing. Are your moons tidally locked?
They're tidally locked, I'm talking about the time it takes for them to rotate around the earth, which really is dependent on mass.
Going around in an orbit is called “revolving “ and “revolution “. Earth revolves around the Sun once a year.

“Rotating” and “rotation “ refer to spinning around an axis. Earth rotates once a day.

Tidal locking makes the rotational period and the revolutionary period equal. The Moon revolves around the Earth once a month. It also spins on its axis once a month; thus it always keeps the same face to the Earth.
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Re: (C&C) Q&A Thread - Quick questions go here

Post by Axiem » Tue 17 Jul 2018, 18:10

Ahzoh wrote:
Tue 17 Jul 2018, 17:14
They're tidally locked, I'm talking about the time it takes for them to rotate around the earth, which really is dependent on mass.
Yes, the (theoretical) orbital period is a function of the masses of the two bodies and the distance between them. The general nomenclature is still to refer to a body's orbital period not its rotational period (especially because of things like libration) even when the body is tidally locked to some larger body.

(And, as eldin pointed out, "revolution" is the word to use for a body going around another; "rotation" is used for a spinning body)
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Re: (C&C) Q&A Thread - Quick questions go here

Post by LinguoFranco » Mon 06 Aug 2018, 03:53

I want to present a magic system I'm working on for a critique, but I'm concerned about people stealing my ideas.
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Re: (C&C) Q&A Thread - Quick questions go here

Post by shimobaatar » Mon 06 Aug 2018, 04:05

LinguoFranco wrote:
Mon 06 Aug 2018, 03:53
I want to present a magic system I'm working on for a critique, but I'm concerned about people stealing my ideas.
I'm sorry to hear that's a concern. What would you like us to do?
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Re: (C&C) Q&A Thread - Quick questions go here

Post by this_is_an_account » Tue 14 Aug 2018, 20:22

Another question: Is there such a thing as a dualative (dualitive?) derivation? Like a collective, but instead of turning "a tree" into "a group of trees," it would turn it into "a pair of trees."
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Re: (C&C) Q&A Thread - Quick questions go here

Post by shimobaatar » Tue 14 Aug 2018, 20:58

Some languages have a dual number, but, in my experience, the dual typically refers to an inflectional category more akin to singular and plural than a derivational collective. However, that isn't to say that there aren't any languages with a derivational process turning "X" into "a pair of X(s)". I just can't think of any off the top of my head. Even if there aren't any, though, your idea doesn't sound unrealistic at all to me. [:)]

By the way, questions about languages would probably be better suited for this thread or this thread.
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Re: (C&C) Q&A Thread - Quick questions go here

Post by sangi39 » Tue 14 Aug 2018, 21:00

this_is_an_account wrote:
Tue 14 Aug 2018, 20:22
Another question: Is there such a thing as a dualative (dualitive?) derivation? Like a collective, but instead of turning "a tree" into "a group of trees," it would turn it into "a pair of trees."
There's a dual number in some languages which means "two of a thing". Proto-Indo-European had it, as do some of its descendants, but IIRC that's more inflectional than derivational (then again, so is the collective in some languages).
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Re: (C&C) Q&A Thread - Quick questions go here

Post by this_is_an_account » Tue 14 Aug 2018, 22:31

shimobaatar wrote:
Tue 14 Aug 2018, 20:58
By the way, questions about languages would probably be better suited for this thread or this thread.
Oops! I thought I was in the conlang section. My bad.
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Re: (C&C) Q&A Thread - Quick questions go here

Post by Creyeditor » Tue 14 Aug 2018, 23:28

this_is_an_account wrote:
Tue 14 Aug 2018, 20:22
Another question: Is there such a thing as a dualative (dualitive?) derivation? Like a collective, but instead of turning "a tree" into "a group of trees," it would turn it into "a pair of trees."
Just to give another answer. In Mee (Trans-New Guinea; Papua, Indonesia), you can suffix a reduced form -ija of the number two wija to a word, to mean something like 'a pair of X'. It is used for days and months as well as certain other more conrete things that appear in pairs.
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Re: (C&C) Q&A Thread - Quick questions go here

Post by this_is_an_account » Wed 15 Aug 2018, 01:54

Creyeditor wrote:
Tue 14 Aug 2018, 23:28
this_is_an_account wrote:
Tue 14 Aug 2018, 20:22
Another question: Is there such a thing as a dualative (dualitive?) derivation? Like a collective, but instead of turning "a tree" into "a group of trees," it would turn it into "a pair of trees."
Just to give another answer. In Mee (Trans-New Guinea; Papua, Indonesia), you can suffix a reduced form -ija of the number two wija to a word, to mean something like 'a pair of X'. It is used for days and months as well as certain other more conrete things that appear in pairs.
Interesting. Does it have similar constructions with other numbers, or is this the only one?
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Re: (C&C) Q&A Thread - Quick questions go here

Post by Creyeditor » Wed 15 Aug 2018, 08:21

It has somethin similar with three, though the distribution is more limited.
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Re: (C&C) Q&A Thread - Quick questions go here

Post by Dormouse559 » Wed 15 Aug 2018, 08:47

this_is_an_account wrote:
Wed 15 Aug 2018, 01:54
Creyeditor wrote:
Tue 14 Aug 2018, 23:28
this_is_an_account wrote:
Tue 14 Aug 2018, 20:22
Another question: Is there such a thing as a dualative (dualitive?) derivation? Like a collective, but instead of turning "a tree" into "a group of trees," it would turn it into "a pair of trees."
Just to give another answer. In Mee (Trans-New Guinea; Papua, Indonesia), you can suffix a reduced form -ija of the number two wija to a word, to mean something like 'a pair of X'. It is used for days and months as well as certain other more conrete things that appear in pairs.
Interesting. Does it have similar constructions with other numbers, or is this the only one?
Latin has forms for various numbers of years and days. They involve adding a number prefix to an irregular form of the root and changing the declension. So annus "year" becomes biennium "two years", triennium "three years" … millennium "one thousand years". Dies "day" becomes biduum "two days", triduum "three days" and so on.
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Re: (C&C) Q&A Thread - Quick questions go here

Post by Micamo » Wed 15 Aug 2018, 10:32

LinguoFranco wrote:
Mon 06 Aug 2018, 03:53
I want to present a magic system I'm working on for a critique, but I'm concerned about people stealing my ideas.
A few points to consider:

1. No one cares. This is not meant to be an insult, but to say that folks are generally too wrapped up in their own projects and ideas to pay much attention to what other folks are doing, let alone go out of their way to "steal" an idea.

2. It's highly doubtful that your idea is so original that nothing like it has ever been done before. There are probably dozens of fantasy novels that have tried to do something similar to what you're doing. This isn't an insult either: The heart of a good fantasy story lies not in how original its concepts are. Once you realize that, you'll be free to focus on what really matters.

3. If you really, really don't want to expose your work to the public, you can PM me if you like and I'll give my comments there.
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