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Thread: Fictional World Help

  1. #1 Fictional World Help 
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    Hey guys, my name is Kanon and I am working to be a writer dealing with both fantasy and sci-fi. I've been building my world for a while now, but there still a lot of things I am struggling with to understand, either because the scope of it would require a lot of research or because I don't know where to start my research which is why I am here on the science forum! The world I am building heavily relies on our world physics even though the universe I am creating is completely fictional. To that end, that is where these series of questions will be coming from within this thread.

    First Question:
    So I've had it in my mind now that the world I'm working on has 5 moons, but the planet itself has an earth like environment. With that, I am trying to figure out if its even possible for a planet to have an earth like environment with that many moons. Does it depend on the size of the planet? Size of the moons? A combination of both? I actually did throw around some numbers for planet size and moon sizes, and when I asked someone else about it about a year ago, though told me to look into "orbital resonance" and that's turning into one of those things I've been finding hard to grasp. Any help or suggestions on that subject?


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    Quote Originally Posted by BlackBaronBlocker View Post
    Does it depend on the size of the planet?
    To be Earthlike would depend on the size of the planet to some degree.
    Quote Originally Posted by BlackBaronBlocker View Post
    Size of the moons?
    Yes.
    Consider the rather impressive effect that tides have given us.
    If Earth had several large Moons (assuming it could for the moment) what kind of tidal war would they be playing with the Earth caught in the middle?
    The conditions here wouldn't be what we consider to be "Earthlike."
    Earth can have five small but visible to the naked eye Moons. Or you could have a tiny moon around another moon.
    Quote Originally Posted by BlackBaronBlocker View Post
    though told me to look into "orbital resonance" and that's turning into one of those things I've been finding hard to grasp. Any help or suggestions on that subject?
    I'd suggest asking which details are troubling you with pointed questions.


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    If the earth had 5 moons, they would not each orbit the earth independently. Their gravity would affect each other's orbit, so it would be unstable unless they got into a resonance.

    This discusses the resonance of Jupiter's 3 moons.
    From Quarks to Quasars » The Galilean Moons of Jupiter
    Three of the moons, Io, Europa, and Ganymede (listed from closest to furthest from Jupiter) orbit with a 1:2:4 orbital resonance respectively. A resonance occurs when the gravity of two or more orbiting bodies periodically act on each other in a similar way. This basically means that, for every four orbits Ganymede makes, Europa orbits twice and Io orbits once. Approximately every seven days, these three moons are in the same position as they were the previous week.
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  5. #4  
    Universal Mind John Galt's Avatar
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    One of the reasons mutiple moons work on Jupiter is that it is large. The mass of the moons relative to Jupiter is tiny. I suspect that to achieve stable orbits for moons of the Earth, despite resonance, one would need realtively small moons. Keep in mind that the Earth's moon is relatively by far the largest moon in the solar system. Also note that two of the four terrestrial planets have no moons, and Mars has only two small captured asteroids that will eventually hit the planet. (At least one will, for sure. Details, I#m sure, available via Google.)
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    Moderator Moderator Cogito Ergo Sum's Avatar
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    Quote Originally Posted by John Galt View Post
    Keep in mind that the Earth's moon is relatively by far the largest moon in the solar system. Also note that two of the four terrestrial planets have no moons, and Mars has only two small captured asteroids that will eventually hit the planet. (At least one will, for sure. Details, I#m sure, available via Google.)

    "Phobos is nearing Mars at a rate of 1.8 m every hundred years; at that rate, it will either crash into Mars in 50 million years or break up into a ring."
    (cf. Solar System Exploration: Planets: Mars: Moons: Phobos: Overview)
    "The only safe rule is to dispute only with those of your acquaintance of whom you know that they possess sufficient intelligence and self-respect not to advance absurdities; to appeal to reason and not to authority, and to listen to reason and yield to it; and, finally, to be willing to accept reason even from an opponent, and to be just enough to bear being proved to be in the wrong."

    ~ Arthur Schopenhauer, The Art of Being Right: 38 Ways to Win an Argument (1831), Stratagem XXXVIII.
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  7. #6  
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    Quote Originally Posted by Cogito Ergo Sum View Post
    Quote Originally Posted by John Galt View Post
    Keep in mind that the Earth's moon is relatively by far the largest moon in the solar system. Also note that two of the four terrestrial planets have no moons, and Mars has only two small captured asteroids that will eventually hit the planet. (At least one will, for sure. Details, I#m sure, available via Google.)

    "Phobos is nearing Mars at a rate of 1.8 m every hundred years; at that rate, it will either crash into Mars in 50 million years or break up into a ring."
    (cf. Solar System Exploration: Planets: Mars: Moons: Phobos: Overview)
    Phobos orbits faster than Mars rotates. This results in a tidal interaction which transfers angular momentum from the moon to Mars, causing Phobos to drift in towards Mars. Deimos, on the other hand orbits slower than Mars rotates, and the tidal interaction goes the other way, transferring angular momentum from Mars to the Moon. This acts to push the moon away from Mars.
    "Men are apt to mistake the strength of their feelings for the strength of their argument.
    The heated mind resents the chill touch & relentless scrutiny of logic"-W.E. Gladstone


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    Good science fiction tells a story. It does not make endless, unnecessary explanations to the reader. Nobody really cares why the sky is blue. Nobody will care why it is green if that were part of your story. All you have to do is make it plausible. Concentrate on making your characters and their interactions believable. You'll win every time. Good luck!
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  9. #8  
    Forum Professor Daecon's Avatar
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    As long as your story is internally consistent both with logic and within its own laws, any deviation from real-world physics can be put down to artistic license.
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  10. #9  
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    You did say that was your first question. . . Is there another?
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    I'd say the overall setting is important, not minor details.
    I can't claim to really know the matter but I suppose if there was a gravitational equilibrium between the moons and the planet it could work.
    Not to mention there is a certain degree of freedom when writing fiction, so unless something is obviously nonsense, no one will complain or even care if some details are off.
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  12. #11  
    precious sir ir r aj's Avatar
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    what will be the names of moons? Are you making sequel to Avatar.
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    Perhaps you should not have an "Earth-like" planet, but merely a live planet with life to which resembles and reminds people of Earth. that way, you can bend the rules from time to time all while remaining consistent to reality (effects of gravity, etc.). Besides, isn't that the beauty of sci-fi and fantasy? its ability to manipulate the world around it to be as we have never seen but still believable- - or even unbelievable.

    For the research. look into nasa. there is a tone of info about our world and the moon. also look into Jupiter and other worlds close by that have multiple moons. I am sure there could be information on them and how their moons influence a planet's atmosphere.
    here is another web site: Could an Earthlike planet reasonably have two Luna-sized Moons? [Archive] - Cosmoquest Forum
    the link follows to a discussion about an earth-like planet with two moons.

    here is a little tid bit about magnetic fields and moons:
    Magnetic fields are crucial to exomoon habitability

    here is a recent event for Earth:
    Mysterious 'Second Moon' In Orbit Around Earth Turns Out To Be Man-Made

    And don't be afraid to add the setting into the story line. That could be a cool bit. the impossibility of life is what makes it special.

    These things should push the story anyways. If it does not push the story, then, as others have stated above, keep it short and sweet to emerge the reader into the vision you want them to have. Great explanation into why things happen about the world around your characters is not going to matter too much less it plays a huge role in your story.

    Good luck. I look forward to reading your book.

    Also, use your name in the story as is, or backwards. that would be awesome. your name is cool
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