USA Today: Five spacecraft that flew past the Earth have each displayed unexpected anomalies in their motions, similar to that of the Pioneer spacecraft when they left the solar system. The anomalies consist of a tiny but unexplained constant acceleration toward the sun. "There's definitely something going on," says Montana State University physicist Ronald Hellings, "Whether that's because of new physics or some problem with the model we have is yet to be worked out, as far as I know. A lot of people are trying to look into this."