Revising the gravitational constant

Nature : The Paris-based Committee on Data for Science and Technology ( CODATA ), which recommends values of physical constants every four years, may be revising the gravitational constant G come 2011. First measured by British physicist Henry Cavendish in 1798, who used a torsion balance, the value for G has increased only modestly since that first experiment. Two different methods are now challenging the most precise measurement made to date, one using a laser interferometer and one using a torsion pendulumâmdash;and the two new values are in striking disagreement with both the earlier value and each other. Nature‘s Eugenie Samuel Reich discusses the discrepancy.