In a secluded valley near Penticton, B.C., a team of Canadian scientists is going after the big picture - no, make that the BIGGEST picture. Using a radio telescope of novel design, the group aims to build a three-dimensional map of the universe ranging from 7 to 11 billion light years from Earth, the largest volume of space surveyed to date. Their goal is to home in on a turning point in cosmic history, when the expansion of the universe mysteriously began to accelerate. Understanding what is causing the acceleration is considered one of the most pressing - and challenging - problems in physics. "This really is the frontier," says Matt Dobbs a cosmologist at McGill University who is working on the electronics behind the new telescope. "We're looking at the place where a big discovery could be made." Construction of the telescope began last week following confirmation on Jan. 15 from the Canadian Foundation for Innovation that it will underwrite 40 per cent of the project's estimated $11.5-million price tag - a modest sum relative to most large experiments in astronomy and physics. The remaining funding will come from provincial governments and other sources. Dubbed the Canadian Hydrogen Intensity Mapping Experiment, or CHIME, the telescope's objective is to map the clouds of hydrogen gas that are known to permeate the cosmos in a web-like structure. Although invisible to optical telescopes, the gas emits a telltale radio signal that astronomers can use to pinpoint position on the sky and distance in space, the information needed to build a 3D map.