... Tonight's Sky . ... Dave's Universe . ... Astronomers measure the universe's deceleration before dark energy took over . First time, researchers can see how dark energy worked at a time before the universe's current acceleration started. ... What is fascinating about the new result is that, for the first time, astronomers see how dark energy worked at a time before the universe's current acceleration started. ... Only registered members of Astronomy.com are allowed to comment on this article. ...