It would be an understatement to say there's been a long build-up to the moment when Voyager 1 ventures into interstellar space: scientists thought the probe was on the edge back in 2010, and we've been waiting for the official milestone ever since. Researchers at the American Geophysical Union now believe that the spacecraft may have crossed that symbolic border months ago. Measurements from August 25th onwards show a steep drop in the detected volume of cosmic rays from the heli
