Extra-solar probes Pioneer 10 and 11 have been confusing astrophysicists for the last decade: they're slowing down a lot more than we'd expected as they're leaving the solar system. The slowing has become know as the "Pioneer Anomaly." (But you probably know it by the popular formula, "Ol' (8.74±1.33)×10^−10 ms^−2".) » 3/31/11 11:40am 3/31/11 11:40am