Mystery over Universe’s expansion deepens with fresh data

Mystery over Universe’s expansion deepens with fresh data

Davide Castelvecchi

A long-awaited map of the Big Bang’s afterglow fails to settle a debate over how fast the Universe is expanding.

“It’s always good to have independent checks, and I think this really provides it,” says Wendy Freedman, an astronomer at the University of Chicago in Illinois and a standard-candle pioneer. Adam Riess, an astronomer at Johns Hopkins University in Baltimore, Maryland, who has led much of the cutting-edge work on standard candles, says that the ACT data’s agreement with Planck is “reassuring” and “a testament to the quality of the experimenters’ work and carefulness”.

But the tension on the Hubble constant remains. Techniques developed by several teams, including one led by Freedman, could help to resolve it. Steinhardt thinks that the measurements will eventually converge as experimentalists perfect their methods.

But Riess says that perhaps it is cosmology’s standard model that is wrong instead. “My gut feeling is that there’s something interesting going on.”