According to General Relativity, the presence of mass curves space, and this curvature causes the effects of "gravity". Do Einstein's equations give us a clue as to the mechanism by which mass is able to do this? In other words, how does mass curve space? How does it "know" to curve space? And why is it that more mass results in more curvature? The source of these questions comes from a reflection upon the old Newton's Law of Gravity. Newton's Law of Gravity provided a very accurate quantitative description of gravity, but did nothing to account for the cause of gravity (aside from the construct of the "field" later on). General Relativity is supposed to clear this up by suggesting that gravity is caused by curved space due to the presence of mass. This doesn't seem to be a complete answer though.