Evolving dark energy?

Don't be surprised if you keep reading astronomy stories in the news this week -- the annual meeting of the American Astronomical Society is underway in Washington DC, and it's common for groups to announce exciting results at this meeting. Today there was a provocative new claim from Bradley Schaefer at Louisiana State University -- the dark energy is evolving in time! (Read about it also from Phil Plait and George Musser.) Short version of my own take: interesting, but too preliminary to get really excited. Schaefer has used gamma-ray bursts (GRB's) as standard candles to measure the distance vs. redshift relation deep into the universe's history -- up to redshifts of greater than 6, as opposed to ordinary supernova studies, that are lucky to get much past redshift 1. To pull this off, you want "standard candles" -- objects that are really bright (so you can see them far ...