Lensing approach to the Hubble constant The current expansion rate of the Universe is parametrized by the Hubble constant, H ₀ . Different methods of measuring H ₀ produce results that disagree with each other, which could be a sign of new physics or of systematic errors in the methods. Jee et al. have analyzed two gravitational lensing systems to determine their distances (see the Perspective by Davis). They use these as benchmarks for a measurement of H ₀ . The precision is not sufficient to resolve the debate but does bypass some of the systematic uncertainties. Observations of more lensing systems will be required to narrow down the value of H ₀ . Science , this issue p. 1134 ; see also p. 1076