With the novel The Hammer of God comes an appreciable although eclectic appendix of sources and acknowledgments in which Clarke accounts for some documented impacts of meteorites on Earth, for film, print, and astronomical software precedents for other aspects of the novel, and for details about asteroids traveling within the solar system — details revealed just after he finished his book manuscript.

The idea of an asteroid threatening Earth is not new, but as the economic and political tides of international relations ebb and flow, the possibilities of nations combining their resources to explore the solar system and expand the range of territory accessible to human beings also ebb and flow. In the 1990s, American and Russian space programs have each included astronauts from other nations and, occasionally, have mounted joint activities.

Numerous satellites have been launched for civilian telecommunications purposes, for weather and geographical analysis...