How is the new time line created by Nero's presence in the past even created, especially since we have 29th Century "time police" scanning the space/time continuum for any anomalous readings? Shouldn't have a Federation Temporal time ship have repaired that time line? Or since it is an "alternate time line that is created by the type of time travel (sling shot effect, temporal anomaly within the reality, or passage through a black hole), does the Temporal prime directive not matter since the changes in the time line effect a different reality? I hope this is clear, because now I need an asprin.