Entropic cascade failure

Temporal entropic cascade failure is a side effect that can occur when traveling to alternate realities. It is caused by the increased entropy created by multiple versions of the same person in one reality. The effects, which only affect the non-native versions, continue to get worse over time eventually resulting in death. The only way to prevent this is for them to go back to their own reality.

Dr. Samantha Carter experienced this when she traveled through the Quantum Mirror to our reality.

In 2006, when multiple SG-1 teams emerged from the Stargate, Dr. Lee speculated that entropic cascade failure did not occur because of the proximity of all the realities to each other.