shutsumon (shutsumon) wrote in specficwriters, @ 2008-05-28 18:13:00 |
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Entry tags: | fantasy, worldbuilding |
Moons, tides and maths. I hates the maths.
Note 1: using Luna to denote Earth's moon because otherwise this post might get a little confusing.
Note 2: I want the answers to the maths not links to the maths. I am a bear of very little brain and complicated equations like that scare and confuse me.
Note 3: The World itself is basically Earthlike in gravity and climate. Probably size as well unless it's density is different which isn't impossible.
Note 4: I'm writing Fantasy not SciFi. I just happen to believe that unless they are following totally different laws (like a world where the aristolean/ptolemian view of the world is correct or one with a flat world or other fun but impossible fantasy models) a world should be scientifically plausible except where magic or miracle is directly involved. In other words don't suggest magic or miracle as solutions unless you want me to get very angry because you obviously haven't read this bit. I need my satellites to be stable without some god or magician constantly having to adjust their position.
Anyway I want this world I'm building to have two moons. Now obviously that could do weird things to the tidal forces but we'll get to that in a minute since I'm not sure how much of an effect moon two would have.
The first moon is larger than Luna and about the same density but equally a little further away so it appears about the size of our moon appears from Earth. Its chemical compisition makes it red and gives it a high albedo... I haven't worked out why yet. I'm thinking it maybe has enough of a tenuous atmosphere of some appropriate gas to cause this. I probably need some maths help here since the moon of terrestrial planet can only get so large and so far away before it becomes impossible and I'm probably pushing the upper limit of this. This moon probably isn't tidally locked and will take more than lunar month on Earth but I need help with the maths.
The second moon is also quite bright but is the more traditional white and is about the size of the dwarf planet Ceres (can be smaller if needed but not by much I want it to be relatively round) and nowhere near as dense as Luna - so obviously it orbits much closer than our moon but probably still looks smaller than Luna looks from Earth. This second moon also has an highly inclined orbit - possibly even a polar orbit making it extremely useful in navigation. I guess it's not a luna-type moon but possibly a captured asteroid - a very big asteroid - that came in at just the right angle to be caught rather than hit or wander off again?
Questions:
1. Is this actually possible? (I don't mind improbable as long as it's even remotely possible). If not which bits are impossible. is it fixable.
2. Assuming it is would "moon two" actually have much of an effect on the tides in general given it's small size and density or only when it came into conjunction with "moon one"? If so how much.
3. How large/far away could "moon one" be to look about the same size as luna while actually being larger assuming similar density? Would the extra distance mitigate the extra mass's gravitation effect on the tides or would the tides be bigger? Roughly how long would it's orbital period be and its phases?
4. Similar information on "moon 2"'s orbital period and phases is also needed. "Moon 2" probably would be tidally locked.
5. Anyone know any decent software to model such things that don't require maths ability to use?