New Scientist Premium- Have we got gravity all wrong? - Features

New Scientist Premium- Have we got gravity all wrong? - Features: "SLAVA TURYSHEV is a man on a mission. Two missions in fact. The researcher from NASA's Jet Propulsion Laboratory in Pasadena, California, is about to re-fly the two most controversial spacecraft in history. The Pioneer 10 and 11 probes were launched in 1972 and 1973 and are now drifting in deep space beyond the outermost planets of the solar system. NASA lost contact with Pioneer 10 in 2003, but though the probes are now long gone, they are anything but forgotten. That's because Pioneer 10, when last heard from, seemed to be off course by around 400,000 kilometres and nobody has ever been able to figure out why. Did some malfunction nudge the craft off its expected trajectory, or are there deeper forces at work?