Temporal distortion grid
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A temporal distortion occurred when two dimensions interacted with one another. When one occurred, the observer might be able to catch a fleeting glance into "another world". An example of a temporal distortion were ghosts: ghosts were perceived as visitations from the afterlife that were, in reality, two dimensions existing simultaneously and temporarily coexisting.
Certain models of TARDIS couldn't penetrate a Temporal Distortion Grid; a Type 40 couldn't break through, but later models like the Type 70 could. (AUDIO: Singularity)
