More Cans Of Worms

"Star of the Sea," which I am currently rereading, does not fit into the successive timelines theory of time travel which I think does account for everything else that happens in Poul Anderson's Time Patrol series although that theory has its problems. If we pull at a single thread, then the entire fabric starts to unravel.

The Successive Timelines Theory

A time traveller who travels into but does not change the past remains in timeline (i). A time traveller who changes the past thereby transports himself to timeline (ii) which is identical with timeline (i) except for any changes made by the time traveller, the first such change being his arrival. Timeline (ii) succeeds timeline (i) in a second temporal dimension just as a later three-dimensional state of the universe succeeds an earlier 3D state in the first temporal dimension.

In "Brave To Be A King," Cynthia Denison consults Manse Everard because Keith Denison has not returned from ancient Persia in timeline (i). We later learn that Keith was detained in ancient Persia because he was forced to play the role of Cyrus the Great. It follows that, in timeline (i), Keith played that role until Cyrus's historically recorded death. Everard departed into timeline (ii). Therefore, he also failed to return home in timeline (i). In timeline (ii), Keith departed with Everard at what would have been about the midpoint of Cyrus's career. Therefore, in timeline (ii), Cyrus did not die in battle but disappeared much earlier. Any Time Patrolman who, returning futureward from the further past, found himself in timeline (ii) would investigate but would find that the change was authorized and would return futureward into timeline (iii). In timeline (iii), the original Cyrus is not killed in infancy and plays the role of himself for his whole career.

Clearly Poul Anderson does not intend to imply all these discarded timelines but I think that they must be there in the past of the second temporal dimension.