Alright, so here's the situation: I'm a writer, and I want to write in a setting on a planet that isn't the Earth. To be more exact, I want it to be larger than the Earth. But I want to have credible writing, rather than claim that magic has made everything stable and feeling like the Earth. As such, I have a few questions. For ease of use, let's call this planet Dirt. 1. If the circumference of Dirt is twice as long as the circumference of Earth, would Dirt need to rotate twice as fast on its axis in order to have days and nights of the same length, given equidistance to its primary light source and the same degree of rotation? 2. If Dirt does have the doubled circumference, how much larger would its volume be compared to Earth's? 3. If Dirt is spinning faster than Earth (which I assume it would be) would the centrifugal force at its outer crust have any tangible effect on the beings living there, e.g., "less" gravity than a planet its size would have, thus causing taller creatures to evolve? To be honest, I'll probably have more questions, but I'll start with these. Oh, and thankxs in advance!