What can't be causing the gravity anomalies
Scientists rule out some explanations for these strange occurrences.
In "Is there something we don't know about gravity?", author John D. Anderson discussed how unpredicted trajectories of the Pioneer spacecraft — among other oddities — might require a new theory of gravity. But what have scientists determined can't be the cause of these gravity anomalies? Claus Lämmerzahl, Hansjörg Dittus, and Oliver Preuss studied and dismissed a number of possible explanations for why spacecraft flybys aren't following predictions.