Brief expositions of two prior Earth-meteorite collisions ground the novel's main premise in historical reality: the Tunguska, Siberia impact of June 30, 1908, and prehistoric reality, an impact at Chicxulub on the Yucatan Peninsula of Mexico sixty-five million years ago. A near miss is cited in the chapter "Oregon 1972." However, the specific location from which a tourist captured the passage of the meteor on film is said to be "Grand Teton National Park," which lies in the State of Wyoming — leaving the reader to ponder whether the meteor's lowest point in trajectory came while it passed over Oregon, or whether the author inadvertently relocated a national park. Clarke's acknowledgments cite additional strikes and near misses, and the published concerns of government agencies and academic astronomers which have led to discussions of a possible Spaceguard Survey intended to identify moving bodies in space which could pose a serious threat to Earth's inhabitants.
While the asteroid threat is the dominant issue in the novel, other motifs inhabit the plot and the "historical" summaries which fill in the technological and socio-cultural backgrounds for the life in the year 2110. Clarke gives brief explanation of "Chrislam," a religion born of American contacts with Islamic culture during the Gulf war in the early 1990s, mixing premises of Judaism, Islam, Christianity, and Buddhism, and propagated rapidly and intensely through Brainman memno-chip programs which can carry virtual reality experiences to the user's brain via a special neural net helmet. Unnamed radicals from among the Reborn, a fundamentalist sect of Chrislam, complicate the novel's plot by sabotaging the mission to deflect the asteroid Kali from its collision course with Earth. The Reborn believe that the attempt to save the Earth is an attempt...
(The entire section is 744 words.)