Possessives and Attributives
Q. Please state which of the following is the correct usage, sun and earth’s gravity or sun’s and earth’s gravity.
A. Since the sun and the earth each possesses its own gravity, make them each possessive: “the sun’s gravity and the earth’s gravity,” or, more concisely, “the sun’s and earth’s gravities.” When you refer to a single item that two subjects share, a single possessive serves: Claire and David’s house.
