1. J.W.Exeter
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    J.W.Exeter Member

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    My little parallel world

    Discussion in 'Setting Development' started by J.W.Exeter, Aug 31, 2014.

    My little moon-world (called the World) has roughly 33% of our Earth's mass and gravity, 40% the size, and 200% the atmospheric pressure at sea-level.

    It orbits a much larger gas giant (size and mass pending)

    Although our Earth exists "somewhere out there ", the world runs on its own periodic table of the elements, similar in many aspects to ours, but quirky in its own way.

    So, I have a few problems here.

    The first:

    When the world orbits behind the gas giant, a sort of "long night" occurs, lasting a little less than 5 days (light would bend around the gas planet and find its way to the moon, making the nights shorter than the days, like here on Earth, but more pronounced)
    Obviously, heat would be an issue. Well sort of. My little world has already a thick atmosphere, so the greenhouse Effect would also be more intense than on earth. Just not quite sure how low the temperature should drop. Also not quite sure how many "regular days" the planet would have before the long night.

    Which leads me to the second problem.

    Time

    Here's a very short kinda table I rigged up.

    One beat = 1.57 Earth seconds

    One moment (100 beats) = 157 seconds (2.6 minutes)

    One hour (100 moments) = 4 hours and 21.66 minutes (4.3 hours)

    One day (10 hours) = 43 hours and 36.66 minutes (43.61 hours)

    One Long Night (5 days) = 9 days 2 hours 3 minutes and 33 seconds (9.09 days, 218.06 hours )

    All these numbers can change. Right now they're pretty close to "desired values" though.

    There's also the issue of gravity too. Since the moon-world orbits a much larger planet, the gravitational pull is going to have a serious Effect on the tides, which is a serious thing because the majority of the surface of this moon-world is covered with an acidic liquid very similar to hydrochloric acid (the Acid Sea, it's called by the denizens)

    While very dangerous, the acid is very useful in a variety of applications not normally achievable without the advent of modern chemistry. But, I also don't know how acidic it actually is. What would the beaches look like? Would the shores all be rocky cliffs slowly eroding over time from the rise, swell and smash of the acidic waves on the shore?

    Getting a bit confused here. But as you can see, oftentimes one thing will lead to another. I have other concerns but for now I'd like some input on the above-mentioned setting.
     
  2. Wreybies
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    Wreybies The Ops Pops Operations Manager Staff Contest Administrator Supporter Contributor

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    My first question would be (since you are paying attention to details) how did a moon of the size you describe hold on to such a thick blanket of atmosphere? If it orbits a gas giant of the size of Jupiter (or larger) you also have radiation to deal with. Jupiter is witheringly radioactive. If this world is inhabited by settling humans, the long night is thing to deal with. If the world has its own denizens about whom you will write, the long night will have played a part in how they evolved, so that will be a thing to think about. Acids are highly reactive. If there is an acid sea, you're going to want to come up with something that explains how life there deals with it. Like on Earth, oxygen is extremely reactive. It's a slutty element. It hooks up with anything that will give it the time of day. Without photosynthesis from plant life to cleave oxygen off as a waste product, free oxygen would very quickly deplete out of the atmosphere, leaving only nitrogen and a few trace gases. Not a friendly place for us. Likewise, your acid sea needs replenishing. It could easily be a byproduct of the metabolism of life on the planet, though.
     
  3. J.W.Exeter
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    J.W.Exeter Member

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    You've made some very good points.

    Gas giant was totally wrong of me. Gas dwarf would be more accurate. The gaseous planet is little larger than Earth and has an atmospheric composition very similar to its moon. I'm kinda hoping the gravity well of the larger planet will help the smaller moon retain it's atmosphere. But now I'm thinking maybe I need to increase the mass of the gas dwarf.

    The dominant intelligent species are Earth-human offshoots, originally from Earth, but they were sufficiently isolated during their evolution from earth-humans that inter-breeding is not normally possible (some rare sub-species have this capability).
    So yes, the presence of the long night, the much thicker atmosphere and lighter gravity should all have quite a bit of influence on the indigenous species, but I haven't quite figured it out yet. Also, they do subsist on a base fluid similar to water, but it's found mostly inland and closer to the northern ice-cap. My planet isn't entirely habitable by its humans, but similarly on earth, some species can only thrive in particular environments, so this is not unrealistic.

    The levels of the acidic ocean are depleting but, according to plot, it won't always be an acid ocean. So this is only a temporary thing, though understandably it still requires major attention.

    There's also one major topic you kinda missed. There's no "oxygen". This is my unobtainium; the periodic table of elements in the world is different from that on earth. The two planets don't quite exist in the same universe.
     
  4. Wreybies
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    Wreybies The Ops Pops Operations Manager Staff Contest Administrator Supporter Contributor

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    The gravity well of the larger planet around which your moon orbits won't help the moon hold its atmosphere. They can't share the gravity well in a way that would give the moon greater holding power. It wouldn't work that way.

    No, no. I understood that. I was merely using oxygen on Earth as a parallel for the processes that would affect your acid sea. Both are highly reactive, thus unstable as to amount and presence without there being a mechanism for reintroducing them in a free state against their own nature. ;)
     
  5. GingerCoffee
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    GingerCoffee Web Surfer Girl Contributor

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    This is off the top of my head and I'll edit it after I have time to look up the facts I may have wrong.

    The Sun isn't the main source of heat on Jupiter's and Saturn's moons, friction is. As the larger gas giant exerts gravitational pull on the moon, the crust deforms and the friction of that movement causes heat.

    Moons can also be heated from an internal molten core. And the gravitational forces of the larger planet keep that core molten.

    In addition, the heat in the core of a planet takes longer to cool than just conduction would suggest. That discrepancy on the Earth led to the discovery there was considerable radioactivity in the core that also generates heat.

    As for the atmosphere, that's OK. Saturn's moon, Titan, has thick clouds.

    And I don't see that you mentioned your moon's rotation. The Earth's night and day are due to rotation. The orbit around the Sun, because it is not on a perfect perpendicular plane with Earth's rotation is how we get the seasons. In winter the half of the planet that is colder gets less direct sunlight, the summer half of the planet gets more.

    I do think there would be an effect on your planet when the sun was out vs when your moon was in the gas giant's shadow. You could use the fact the heat is less but comes from the gas giant to solve your moon becoming a frozen wasteland once or twice a month. You might need to address the frequent earthquakes that would be occurring on a moon orbiting that close to a larger body.
     
  6. GingerCoffee
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    GingerCoffee Web Surfer Girl Contributor

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    OK the finer points:

    Titan's atmosphere:
    This reminded me, gravity didn't rob Mars of its atmosphere, the solar wind blew it away. Though the lower gravity would have also contributed as it would have less ability to hold on to the atmosphere.

    Trying to find out about the pull of Saturn on Titan's atmosphere led me here: NASA: Titan's Underground Ocean
    I'll keep looking for the loss of atmosphere to the neighboring giant.
     
  7. thirdwind
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    thirdwind Contributing Member Contest Administrator Reviewer Contributor

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    Hahaha. I bet more students would pay attention in class if you were their science teacher. :D
     
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  8. GingerCoffee
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    GingerCoffee Web Surfer Girl Contributor

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    NOVA - How to Get an Atmosphere
    Turns out you need heat to keep the atmosphere from freezing out and becoming a solid or liquid instead of a gas. And despite the enormous gravity difference, Saturn pulls Titan's atmosphere up from the surface, but Titan's gravity is enough to hold it from going all the way to Saturn.

    Just a guess, but gravity is a weak force and drops off precipitously with distance. So the closer distance may be the thing affecting the balance.

    One way or the other, that article is excellent for understanding the principles of forming and keeping an atmosphere.
     
  9. J.W.Exeter
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    J.W.Exeter Member

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    Thanks so much ginger coffee! You were awesome.
    Thanks to you too wreybies for your input :)

    I might have to either bring the atmospheric pressure down or the gravity of my moon up. But it looks like the larger planet plays a pretty important role in protecting the smaller moon from solar winds. But otherwise it seems like a fairly feasible setting. It doesn't need to be 100 percent correct (it is mostly a fantasy story), but it comes close enough hopefully for the majority of readers.
     

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