Differently equal.

The article looks at attempts to develop a physics theory to reconcile the force of gravity with other properties of mass and motion. Physicist Albert Einstein described this issue as the equivalence principle in his general theory of relativity, positing that gravitational mass and inertial mass under acceleration behave in the same way. Some theorists studying quantum gravity believe that gravitational mass must be distinct from inertial mass. Other topics include the search for a theory of everything which would explain the principles of gravity, research into the Higgs boson field, and physicist William Unruh's theory of the black hole radiation emitted by gravitational or accelerating objects in a vacuum. INSETS: DROP THE SUBJECT;DARK INERTIA.