Pioneer Deceleration: When the Laws of Gravity Failed

In the early 1980s, the Pioneer 10 and 11 spacecraft were hurtling toward the edge of the solar system when scientists noticed something terrifying. The probes were slowing down. The deceleration was microscopic, but it violated everything humanity understood about physics. For decades, the "e;Pioneer Anomaly"e; threw astrophysics into a state of panic. Had we misunderstood Newtonian gravity? Wa...