Five months ago, 15 billion miles away, something interfered with the smooth transmission of data from the Voyager 1 space probe back to Earth. Voyager 1 is the carrier among other things of a gold LP inscribed with tracks by Bach, Beethoven and Chuck Berry, and greetings to aliens from human children in 55 languages. Data had continued to reach Earth since the interference last November, but in corrupted form. Scientists sent up a software workaround that took 22 and a half hours to reach the probe at the speed of light, then waited for a comprehensible reply. It came on Monday, greeted with relief and high-fives at the Jet Propulsion Laboratory in California by some who’d worked on the Voyager programme since the 1970s. They speculate that the original problem may have been caused by a cosmic ray or a failed piece of 47-year-old hardware. But before the data interruption the probe had started sending back signs of a “pressure front” consisting of a strengthening magnetic field and increasingly dense interstellar plasma. The JPL crew called it Pressure Front 2. Could that have caused the problem?