antsy and uncle ham

I learned this week that Celestia does not model gravity. So I’ve started wondering if Celestia could be easily modified to defer simulation executive control and simulation clock/discrete event management to an external entity? This approach might lend itself to an architecture where gravity could be selectively modeled outside of Celestia:

Before reading the above Celestia forum thread, I was also not aware of the Orbiter simulator. It apparently does model gravity, is closed source freeware, but has an API.