A question me and a buddy were pondering the other night. What causes gravity? Is it mass or weight? Would, say, a larger planet made up of gas have a stronger gravitational pull than, say, a smaller planet made up of dense, heavy metals such as lead? Does the mass or the weight determine gravity? Thanks for the help. Non physics guy here just curious about astronomy and such. If I screwed up the terminology, forgive me. Laymen's terms would be appreciated in your answer.