Convergence

Future histories diverge in the near future but some seem to approach re-convergence in their further futures. They cannot re-converge completely in a four-dimensional framework but we only need to imagine a five-dimensional framework. Thus, a time traveler might make the long futureward journey from the eve of World War III to the period of the evacuation of the galactic periphery in Poul Anderson's "The Chapter Ends," then a short sideways-in-time journey to the period of the reseeding of Earth in James Blish's "Watershed," then another short sideways-in-time journey to the period when the human home-planet has been entirely forgotten in Isaac Asimov's Foundation Trilogy. These further future periods share some common features, reflecting the period in which they were written. However, later-written fictional futures can be very dissimilar, as in Anderson's Genesis.