Newton's law of universal gravitation defines **gravity**: *All objects in the universe attract each other with an equal force that varies directly as a product of their masses, and inversely as a square of their distance from each other. *Expressed as a formula: \(\vec{F_{g}} = { Gm_{1}m_{2} \over r^2}\) where r is the distance between the two objects and G is the **gravitational constant** with a value of 6.67 x 10^{-11}.

Newton's law of universal gravitation defines the __________ with a value of 6.67 x 10^{-11}.