From the January 2009 issue

What can’t be causing the gravity anomalies

Scientists rule out some explanations for these strange occurrences.
By | Published: January 26, 2009 | Last updated on May 18, 2023
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.