A third theory embraces the idea that a minute acceleration exists in the velocity of light, which might result in the appearance that the probes are slowing down: if light travels faster, telemetry signals arrive faster, and the craft seem to be closer.

• 第三种理论则认为光速有著很小的加速度，导致太空探测器的减速效应：假如光传播得较快，遥测讯号会较早抵达，使得太空船看来似乎离我们较近。