Hegira (novel)

"Hegira" is a 1979 science fiction novel by Greg Bear (ISBN 0-7592-0684-8). It deals with themes including cyclic time, artificial intelligence, artificial life, and artificial structures of planetary scale.

In the novel, "young" humans (i.e. recreations of the medieval originals) are transported through the Big Collapse at the end of time to seed the next cycle of the universe. They are transported to Hegira, an artificial environment of the scale of Jupiter, which has habitats for several species on its surface. Those habitats are protected and uncoupled from the universe's entropy by means of forcefields projected by giant obelisks. In the human realm these are inscribed with the recorded history of humankind, sorted chronologically from the bottom up, including the science that went with it. People try to understand and copy what they can read on the obelisks, using balloons in some places to reach higher points on the obelisks.

A legend tells the protagonist that his beloved (frozen in stasis) will awaken if he goes on quest to the rim walls of the habitat, so he does. On the way he lands on an island with a good view of an obelisk (at least 1000 miles high) which is just tumbling down in the distance. Its fall causes a tsunami and devastates a continent. After the devastation, the inscriptions at the top of the fallen obelisk about human history are revealed. The hero's quest to the rim succeeds. He makes contact with an AI guardian of Hegira who tells him the story and advises him to go and populate the new universe, having become part of the last one.