Eliminating this substance is the goal of the DGP braneworld model. So-called “phantom” forms of this substance are an extreme case of hypothetical quintessence models. (10[1])An equation of state of pressure equal to negative density characterizes this substance, whose density remains constant as space expands. An era dominated by this substance began roughly 4 billion (-5[1])years ago, when the expansion of the universe began (-5[1])to accelerate. (-5[1])This substance is represented by a quantity that Einstein called his “biggest (-5[1])blunder” (10[1]-5[1])when adding it (-5[1])to his field (10[1])equations, known as the cosmological constant. (-5[1])For 10 points, name this mysterious substance that accounts for (-5[1])over 70 percent (-5[1])of the universe, (10[1])along (10[1])with matter and dark matter. ■END■ (10[4]0[3])