Astrophysicists join forces to measure dark energy

It's an unprecedented experiment aimed at understanding what is causing the acceleration of the expansion of the universe. And it is bringing together University of Toronto astrophysicists from the Canadian Institute for Theoretical Astrophysics (CITA), the Canadian Institute for Advanced Research (CIFAR) and the Dunlap Institute, with collaborators at the universities of British Columbia and McGill, and the Dominion Radio Astronomy Observatory. "The motivation is to make a precise measurement of dark energy and the real hope is that the dark energy is changing with time," said Professor Ue-Li Pen, associate director of CITA. The Canadian Foundation for Innovation will invest $4.6 million to build an innovative new digital radio telescope and make a three-dimensional map of the largest volume of the observable universe to date through a technique being pioneered in Canada called hydrogen intensity mapping. Matching funds from collaborating institutions including the provincial governments will bring the total funding for the experiment, known as CHIME, to $11 million. "CHIME would be a way to see if dark energy is a constant," said Pen. Professor Dick Bond, director of CIFAR's cosmology and gravity program, explained: "the origin of accelerated expansion is inextricably tied to how gravity interacts with the 'vacuum energy' whose nature has been the greatest mystery in physics for eighty years.