[dogscoff]

Thanks everyone, I think I have the spreadsheet working now. For Earth I get a gravity value of 9840866.19 (starting with a diameter of 12756km and density of 5520kg/m^3). For Mars I get 3736591.2 (diameter 6794.4, density 3935). That's exactly right in proportion to one another, but I have no idea whether or not the values themselves are accurate- all the websites that list such data measure surface gravity in comparison to Earth's.
Also, I haven't factored in rotation which (apparently) increases the effective gravitational pull.

I'm still a little fuzzy on the kg-1 s-2, although I now understand that it's just the unit by which gravity is measured. How would you pronounce it? What does that s stand for? Is it seconds?

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Any O&C fans in the audience (if I haven't killed them all off with the lack of updates) may be interested to know that I've now used the spreadsheet to come up with some values for Ceres IV (Plenty).
diameter: ~19000km.
Circumference: ~60,000 km.
Surface area: 2.2 times that of Earth, but I want at least 85 or 90% of it to be water, which leaves betwee 1.15 and 0.77 times Earth's land area. I'll probably go for 90%.
Density: Not sure yet. With an Earth-like density, it would be about 1.5 times Earth gravity (bloody hard work, but probably livable). Interestingly enough, with a Mars-like density, the number comes out only a little above Earth's gravity.

I always intended it to be high in mins and orgs, but very low in rads, so that would fit in well with low density and therefore only-slightly-higher-than-Earth gravity, and it would also help to explain (along with all the beaches) why the place is so damned popular.

Of course, all these numbers are muddied in the text by literary vagueness, so none of them have to be particularly precise.