Eternity (original title: Eternity) is a science fiction novel by Greg Bear published in 1988. This is the second volume of a trilogy that also includes Eon and Heritage.
While the world is recovering slowly from a nuclear war, asteroid Volume of precedent is still in orbit around the Earth, but the way, this shift to a parallel universe, is closed for several decades. The question now arises whether the time is not ripe to reopen the crossing, especially since a mysterious envoy came a distant future just ask for the reopening and destruction.
Moreover, one of the heroine of the previous volume, Patricia Vasquez (the mathematician whose theoretical work led to the creation of the Way), is trapped in a parallel universe, an Earth on which the empire Alexander the Great has survived its founder, has managed to prevent the emergence of the Roman Empire and are still nearly 2,400 years after its founding. After trying to join her world of origin throughout his life, Patricia Vasquez Rhita forward the torch to his granddaughter, who inherited his gifts of a mathematician. Rhita therefore went to Alexandria to convince the empress who ruled over the empire of Alexander to mount an expedition to find a passage to the Way.