A series of brief temporal distortions in which moments repeat themselves, felt across a wide region of space after Dr Paul Manheim's experiments with time and gravity go wrong.
The Manheim Effect is the phenomenon in the Next Generation episode We'll Always Have Paris. The Enterprise and other ships experience short loops in which a few seconds happen twice, and a distress call traces the source to the laboratory of Paul Manheim on a planetoid in the Vandor system.
Manheim has been trying to open a window into another dimension. The accident kills his team and leaves his mind lurching between two realities, while the opening continues to widen and send out distortions.
Data, judged best able to cope with overlapping moments, enters the laboratory and finds three versions of himself from slightly different instants. Choosing the right moment, he drops a canister of antimatter into the rift and seals it. Manheim recovers, watched over by his wife Jenice, a former love of Picard.