Moon proximity and its effect on climate and seasons

[mosquiter]

The story of my novel is set on Earth's twin with one moon which orbits it at a much closer distance than the moon we have around, and its orbit is a bit more elliptical. I wonder:

1. Would it cause gigantic hostile waves alongside sudden tidal shifts? I need the waves to make water travel next to impossible;

2. Would it bring about extreme season and climate changes?

3. Since the twin's moon originates from the part of the planet itself when it suffered a catastrophic explosion close to its core, my theory is that due to the planet's rotation the crater would shape itself into a hole similar to... this (). Would you agree?

The hole, the moon, the seasons and the waves all play an important role in the plot.

 

[chrispenycate]

The tides are generated by the proximity of the moon but also by its absolute mass. The ellipticality of the orbit gives more difference between spring and neap tides, but the difference is dwarfed by the relative positions of the two moons. That is, assuming the orbit of the inner moon doesn't cross the orbit of the outer (a wise precaution if you want the system stable for more than a few million years). Thus, the mass of the moon is critical; if anything like Luna, we've got interesting tidal patterns, and any species intending to develop a civilisation would be well advised to inhabit well up mountains or in ocean depths.

Seasons on the planet are caused by the axial tilt of the planet's rotation (on Earth) plus the eccentricity of its orbit (for a comet, for example). The advantage of the axial tilt method (for generating life) is that the same amount of energy is going into the system, just differently distributed (giving us climate, and lots of weather, but not tending to freeze the atmosphere).

The best time to knock a moon off a planet is while it's still fluid, or at least plastic. So an immense crater, unbalancing the rotation and making it wobble is unlikely. Mostly gravity will pull it back into a sphere (oblate spheroid, them). There might be a mile deep dimple on the surface, but no more imbalance than tectonic plates or pangaea.

There will be waves where tides meet narrow bits of coast, or sudden shallow bits, but most extreme wave activity comes from wind, not tides, and not even tsunami. The tides, though enormous, are predictable (and complex. A major reason for developing mathematics). Still, having a port that's only usable two days a month could be inconvenient.

 

[jastius]

it wouldn't affect interior water travel upon small bodies of water but greater interior lakes would be affected by the lunar tides.
it would also have certain effects upon the female persons.

if a comet or meteoroid blasted out a significant chunk there would be a giant thermonuclear-like explosion that could very well blast molten debris into orbit. however it is questionable whether that would have possess a sufficient mass to create a moon. perhaps if it were to occur in conjunction with a giant asteroid shower, perhaps from another planet's demise, the debris could be collected in several collisions to form an object of acceptable mass.
however any deep hollows of the earth are soon transformed into bodies of water unless there is a cradling effect of the tectonic plate surrounding the area.

 

[mosquiter]

Wow, first of all, thanks for your detailed reply.

The twin's orbit, its axial tilt and the Sun are not very relevant to the story so I probably won't muse much about them. However, I feel relieved that the climate won't scorch the frozen land or vice versa.

I was planning for my civilizations to stick to higher grounds, while the lower land would be constantly bothered by the tides making vast saltwater marshes or temporary saltwater lakes which are difficult to cross.

As for the moon, I do expect its shape to be briefly rolled into a sphere or spheroid, but it is its crater on the twin that I am concerned about. I believe the circular shape of the crater might eventually be modeled into a hole similar to when you take out one clove from a garlic. If not, I may add some tectonic touch to it.

As for the knocking the moon off the planet, wasn't the Saturn's ring formed by the clash of the meteor or some solid object leaving the debris orbiting around it?

 

[mosquiter]

it wouldn't affect interior water travel upon small bodies of water but greater interior lakes would be affected by the lunar tides.
it would also have certain effects upon the female persons.

if a comet or meteoroid blasted out a significant chunk there would be a giant thermonuclear-like explosion that could very well blast molten debris into orbit. however it is questionable whether that would have possess a sufficient mass to create a moon. perhaps if it were to occur in conjunction with a giant asteroid shower, perhaps from another planet's demise, the debris could be collected in several collisions to form an object of acceptable mass.
however any deep hollows of the earth are soon transformed into bodies of water unless there is a cradling effect of the tectonic plate surrounding the area.

I was planning for the explosion to occur close to the core, blasting a significant chunk upwards. It would of course wipe out the life on it and give it a peculiar shape while bleeding a lot of lava around.

 

[Mirannan]

It's also possible that a really large or close moon would significantly affect day length, because there would be a degree of tidal locking of the primary's rotation to the orbit of the moon.

If this didn't happen, and/or if the orbit was markedly elliptical, there might be a lot more in the way of volcanic eruptions because of tidal distortion of the rocks of the primary. (A bit like Io and to a lesser degree Europa in the Jovian system.)

 

[Stephen Palmer]

Excellent documentary.

 

[mosquiter]

An excellent documentary indeed, thank you Stephen!

From how it explains the origin of our Moon, I believe I could make mine with this gigantic internal explosion (I will skip the talk about the sizes, masses and the distance between). I just need to justify the tides, the huge chasm and the big darn thing hovering in the skies. I will let the local prophets explain it in their words.