[Wip/Question] Devoloping "realistic" fantasy worlds - The SV Project

[Robulous]

Interesting. Of course moons large enough to be able to create a constantly replenished ring would only be able to form outside the Roche limit, otherwise they'd boil away too quickly. Your world would therefore need sufficient mass to be able to hold two fairly large moons. Mars has two moons of course but they're tiny - astronomers expect Phobos to fall low enough to break up into a ring around the planet, but this would be a thin debris ring that wouldn't last long.

As far as the size of your planet is concerned, if you want it habitable for humans there's a fairly narrow range for Earth-type life. If it's bigger than Earth the gravity will increase, although you can reduce the gravity by making it less dense. My conworld Helevos is small than Earth, but with an extra-dense core. The density and size of the planet will influence vulcanism, and also how easily useful minerals are in the crust. A large, light world will likely have less easily available metals because they would have sunk to the core - in fiction Robert Silverberg's "Majipoor" is a good example of this.

Astronomer's say the moon was important at stabilising the rotation of the earth - without it as a counterbalance, Earth would "wobble" more, as it spins like a spinning top. Not sure how two large moons would influence your wobble, but it would certainly make tides quite complicated.

The tides and cycles of the two moons would also influence the indigenous life and cultures on your planet. Calendars are often based on phases of the moon, and even the life cycles of plants and animals follow lunar cycles - humans included.

Incidentally I use Astrosynthesis - it's quite useful for juggling size, gravity and density to come up with a realistic world.