Hi. I've been having some difficulty with calculating this equation, mainly because I've forgotten most of the equations over the years, and this is sort of a reverse algebra form of an equation I scarcely remember. (i.e., I'm screwed) Ok, here goes. Assume you have objects, as per satelites(sp?) around a central field. (wewill call this central field a "planet" This planet has a radius of aproximately less than 25pm, or to say, 25 picometers. Some prefer this planet have a radius of 24.2 picometers, but who really cares, right ? The satelites or "moons" passing by this planet have an inertial velocity of 1.8504e10 meters per second. (for the moment, we are just going to have to suspend that whole "C" thing to work out the math) So the question is, what would the gravitational acceleration, have to be, in order to "catch" these moons in an orbit of 25pm. Obviously we don't want much more or less than this number. Buddha says " If planet's gravity is too tight, moon collide with planet; but if planet's gravity is too loose, moon will fly away" one of the things that bugged me about this was that when gravity accelerates, you normally only count the first 50% of distance travelled, but count 100% of the speed from acceleration. if its easier on you, you can use picometers and picoseconds, I started to, before it got too confusing. As far as mass- well, a bowling ball and a feather both fall the same in vacuum, so it doesn't matter what the mass of the "moons" are. All I am ask for the aceleration rate in meters, or picometers, or kilometers, or whatever, at 25 picometers radius, each second.