Scientists are using cosmic ray detectors to uncover the secrets of the earliest large metropolis of the Americas. Archaeologists and nuclear physicists are working together to measure the passage of muons, subatomic particles from deep space, through the 2,000-year-old Pyramid of the Sun to discover whether it was a mausoleum or a ceremonial monument. They believe the experiment will lead them to burial chambers, the American Association for the Advancement of Science conference was told. Many experts believe that the pyramid, the third largest in the world, holds the mysteries of the pre-Aztec Teotihuacan civilisation. Arturo Menchaca-Rocha, the director of...