Mapping cancer as if it were the universe

OVER THE past two decades Alexander Szalay, an astronomer at Johns Hopkins University in Baltimore, has helped create the most detailed maps of the cosmos yet made. His raw material comes from the Sloan Digital Sky Survey, which began in 2000. So far, this project has charted a third of the heavens and observed nearly 1bn astronomical objects.The survey’s telescope, which sits on a mountain top in New Mexico, collects its data by recording the arrival of photons of light on a charge-coupled device. This turns them into an electrical signal that Dr Szalay and his confrères translate into a representation of reality by winnowing out the noise and determining, from what remains, what sorts of objects the telescope is looking at and how far away they are.