Random Factor

"We've identified the random factor that could bring on an avalanching change; what we must do is damp it."
-Poul Anderson, Time Patrol (New York, 2006). pp. 607-608.

In a timeline without a Time Patrol, young Edh would have been raped and killed by Roman sailors. Instead, she is raped but rescued by Janne Floris who has time traveled to Edh's early life to find out what made her an anti-Roman prophetess...

But how did the Patrol know that this period needed to be investigated? In the twentieth century of the Tacitus One timeline, Everard and Floris discussed a document from the Tacitus Two timeline. I have rationalized the time travel paradoxes in the Time Patrol series as far as possible but this scene does not quite fit.

It seems to me that time travelers routinely travel pastwards and futurewards along our familiar temporal dimension and sometimes futurewards but never pastwards along a second temporal dimension. The latter quantum jump occurs only when they enter a new timeline. It seems however that in this story, "Star of the Sea," a Patrol researcher has traveled from the Tacitus One timeline to the Tacitus Two timeline, acquired a document and then returned with it to the Tacitus One timeline. As Everard elsewhen reflects on "the structure of the plenum":

"It seems to be subtler and trickier than they see fit to teach us about at the Academy."
-Poul Anderson, The Shield Of Time (New York, 1991), p. 261.

That reflection is familiar to anyone who has trained and is now learning from the experience of practice.