Designing detailed Astronomy?

[Redrobes]

A lot of these theories that the moon orbits degenerate because of collision and stuff is based on a small but significant probability that there is a collision so running for a long time makes the orbit not possible. But if your in a fantasy setting then I would say that if the orbit is not probably going to cause that collision then just fudge it and say they don't collide even tho there is a small chance they might. It would be like saying that in my fantasy setting with earth and moon setup there are never any solar eclipses. It wouldn't drastically affect the game to make that assertion.

[Talroth]

A lot of these theories that the moon orbits degenerate because of collision and stuff is based on a small but significant probability that there is a collision so running for a long time makes the orbit not possible. But if your in a fantasy setting then I would say that if the orbit is not probably going to cause that collision then just fudge it and say they don't collide even tho there is a small chance they might. It would be like saying that in my fantasy setting with earth and moon setup there are never any solar eclipses. It wouldn't drastically affect the game to make that assertion.

Well, this is kind of the interesting thing about planets and their moons. Even Earth's moon is degrading and will eventually leave orbit (I forget if it is coming toward us, or going to move away and out of orbit) and ones that orbit around Mars are even more unstable.

For a large moon like Earth's, that most likely starts as a major impact, then you ideally have it stable for several million years. But for small ones, they can be 'stable' for far shorter periods of time, even if they're only stable for hundreds of years before going back out of orbit they can still have an impact on society and life.

[Ascension]

The Science Channel used to show Carl Sagan's "Cosmos" quite frequently until being retired this summer. One of his shows was about constellations and how they look totally different from different perspectives...not only in space but also in time and culture. Run the program backwards and Ursa Major doesn't look like Ursa Major at all. Viewed by the ancient Chinese, it was actually three figures (a dragon, a cart, and a tax collector) instead of a bear. Since everything is moving, over time the shape will change and for us the bear will become something else (although that time is thousands of years off).

As to the moon retreating away from us, there was a History Channel show called "If We Had No Moon" (narrated by Patrick Stewart) that says the moon is moving away from earth at about 1 mile per year.