Do we live in a “stop and go” universe?

At the 202nd meeting of the American Astronomical Society, Robert Kirshner (Harvard-Smithsonian Center for Astrophysics), on behalf of the international High-z Supernova Search Team led by Brian Schmidt (Mount Stromlo Observatory), presented evidence that the expanding universe slowed for billions of years before galaxies began accelerating, like cars that get past a bottleneck. “Right now, the universe is speeding up, with galaxies zooming away from each other like Indy 500 racers hitting the gas when the green flag drops and the pace car gets out of their way. But we suspect that it wasn’t always this way,” said Kirshner. John Tonry (University of Hawaii), principal investigator of the team for the new and collected previous observations reported on in May 2003, agreed. “We’ve been hoping to see this effect of slowing in the distant past. We saw evidence 5 years ago that the expansion of the universe currently is accelerating, but we didn’t know for sure what it was doing 7 billion years ago. We are now seeing hints that, way back then, the universe was slowing down.”