It is unthinkable that time travel would intrude in a heroic fantasy like The Broken Sword or that magic would work in the Time Patrol series although characters from the different kinds of universes can meet in the Old Phoenix Inn between universes. How much might the real universe (or multiverse) encompass? A lot, although mothing like what has been imagined. Scientists have had to discover the laws of motion, the electromagnetic spectrum, biological evolution, sub-atomic particles, the strong and weak nuclear forces, quantum mechanics, mass-energy equivalence, relativity including the light speed limit, other galaxies, cosmic expansion, curvature of space, black holes, dark matter and dark energy in a universe where consciousness is not (like gravity etc) a fundamental force of nature but instead is a by-product of natural selection within temporary, local, negative entropy. This real universe is the setting of Poul Anderson's hard sf, including his Technic History where civilizations are entropic. In Norse mythology, which Anderson celebrated, the conflicting but interacting forces of heat and cold are basic whereas consciousness, including deity, is emergent. The entropic and Norse universes come together when an explorer of a globular cluster at the far edge of another spiral arm remembers the myth of fire and ice. See:
In the preceding post, with Anderson as our axis, so to say, we also referred to time travel works by:
(ii) Anyone who is just starting to time travel cannot know whether their timeline is mutable or immutable. Anderson's Jack Havig tries to prevent his father's death before he learns not to try. All the evidence indicates that Audrey Niffenegger's Henry DeTamble also inhabits an immutable timeline. However, wanting to be sure that he will always return to the future in which he is married to Claire, DeTamble takes extra care not to do anything that might change the course of events. Stirling's American time travellers have to find out what kind of timeline they are in. Recruits to Anderson's Time Patrol are told as part of their training.
(iii) Both HG Wells' The Time Machine and Anderson's There Will Be Time, the latter featuring Havig, describe events rushing past a time traveller.
Thus, we compare Anderson with Stirling, Niffenegger and Wells. Anderson's comprehensive treatment of both time travel paradoxes, causality violation and circular causality, makes his works a pivotal point of comparison with other time travel authors.
Now consider a time travel conundrum in Tim Powers' The Anubis Gates. I could have discussed this on the Logic of Time Travel blog but far fewer people would have read it there. In fact, I have tried to redirect readers from that blog to this one: see About Time Travel. We will find that issues raised by Powers have already been addressed in (i) or (ii) above.
Trapped inside a burning tent, Doctor Romany can escape only by jumping through time:
Of course, a time traveller can at least temporarily duplicate himself by coexisting with his younger or older self (see A Case In Point) or maybe by initiating a divergent timeline containing an alternative version of himself.
That is enough about that, I think.
(i) If person A's brain duplicated the interactions in person B's brain, then A would think that he was B, complete with B's memories, motivations etc.
(ii) If an artificial neural network duplicated B's neuronic interactions, then that network would reproduce B's consciousness and sense of identity.
(iii) If some other technology exactly duplicated the effects of neuronic interactions, then that technology would generate self-conscious individuals maybe thinking that they were living on Earth in a particular historical period.
(i) happens in Tim Power's The Anubis Gates.
(ii) happens in Poul Anderson's Harvest Of Stars.
(iii) happens in Anderson's Genesis.
In The Anubis Gates, a character seeks immortality by repeatedly projecting his personality into someone else's body while at the same time displacing that person's personality into his own abandoned and soon-to-die body.
The idea that personalities can be generated and duplicated in these ways links these three novels.
Meanwhile, SM Stirling's The Lords Of Creation, Volume III, The Lords Of Creation, should be en route via eBay. "Poul" and other sf writers have their says at the beginning of Volume I or II as far as I can remember without being able to check the text momentarily.
Contemporary fiction has a single premise: that the contemporary world exists as it does because history occurred as recorded. Sf varies its premises. Poul Anderson's Time Patrol would be unnecessary in The Anubis Gates. How would the Patrol respond to the events of SM Stirling's To Turn The Tide? As a matter of fact, in the Patrol timeline, there is not, as far as we know, any world-wide nuclear war in 2032. Therefore, the Patrol would prevent such a war from occurring and would also, of course, try to prevent any time travellers from changing history in the second century CE.
Good guys in one scenario are bad guys in another.
