This is high school task, to measure "density of infinite layer of material" by measure its gravitational attractive force. One don't need to touch material, b

This is high school task, to measure "density of infinite layer of material" by measure its gravitational attractive force. One don't need to touch material, but need to hang close to it and measure acceleration with some conventional instrument (for asteroid distance will be about few meters and acceleration around millimeters/s^2). Most known appearance in Clarke Odyssey 2001.