New Study Gives Dark Energy A Boost - Science News: Obtaining a precise value of the Hubble constant also places new restrictions on one alternative to “dark energy” as the driving force behind accelerated cosmic expansion, says Riess. In the alternative scenario, Earth and its environs would sit at the center of a vast void a few billion light-years across (SN: 6/7/08, p. 12). That configuration would produce an optical illusion making it appear as if the universe’s expansion is accelerating.
But such a setup would require a significantly lower value of the Hubble constant than the one Riess and his colleagues have now measured to high precision. Previous measurements of the constant were already at odds with the void model, but the added precision of the new study refutes the model conclusively, Riess says.