Galactic illusion helps refine dark energy abundance - physics-math - 24 November 2010 - New Scientist

Galactic illusion helps refine dark energy abundance: "Christian Marinoni and Adeline Buzz at the University of Provence in Marseille, France, realised they could fine-tune such estimates by observing distant galaxy systems in which two galaxies orbit each other. For far-off pairs, assessing the separation of the two galaxies relies on knowing how fast the universe is expanding. Get this wrong, and the result is an optical illusion: the distance between the galaxies appears longer or shorter than its true value."