AFTERWORD

Recently the space elevator, as dramatized in Clarke’s The Fountains of Paradise (1979), has come closer to engineering feasibility. The details given here are based in part on a study funded by NASA’s Institute for Advanced Concepts program, and written up in The Space Elevator by Bradley C. Edwards and Eric A. Westling (Spaego, San Francisco, 2003). See also Leaving the Planet by Space Elevator by Dr. Edwards and Philip Ragan (lulu.com, Seattle, 2006), and papers by Giorcelli, Pullum, Swan, and Swan in the Journal of the British Interplanetary Society, September 2006. A recent study of the use of space elevators as energy-free “orbital siphons” is given by Colin McInnes and Chris Davis in the Journal of the British Interplanetary Society, vol. 59, pp. 368–74, 2006. We’re very grateful to Dr. Edwards for discussions on the relevant sections. His company “Black Line Ascension” may become a real world counterpart of our Skylift Consortium.

It is remarkable that cultures globally appear to share a “world tree” myth. Some of the more plausible explanations for this range from cloud formations to plasma phenomena (see for example www.maverickscience.com/ladder_aeon.pdf).

The “Cyclops” Fresnel-lens telescope is based on a study by James T. Early (“Twenty-meter space telescope based on diffractive Fresnel lens” by Dr. Early et al., in Proceedings of SPIE Vol. 5166, “UV/Optical/IR Space Telescopes: Innovative Technologies and Concepts,” ed. Howard A. MacEwen, January 2004). Our depiction of the Fresnel shield of Sunstorm also drew on Dr. Early’s studies. We’re very grateful to Dr. Early for discussions on these concepts.

Our depiction of Martian exploration draws partly on a conceptual design study, to which Baxter contributed, of a base at the Martian north pole: see Project Boreas: A Station for the Martian Geographic North Pole, ed. Charles S. Cockell (British Interplanetary Society, 2006). The idea that relic space probes could be used to provide human-interest targets for future Mars expeditions was suggested by Baxter (see “Trophy Fishing: Early Expeditions to Spacecraft Relics on Mars,” Journal of the British Interplanetary Society, vol. 57 pp. 99–102, 2004), and the history of humanity’s interaction with Mars is sketched by Baxter in “Martian Chronicles: Narratives of Mars in Science and SF” (Foundation no. 68, 1996, and in The Hunters of Pangaea, NESFA Press, Feb 2004). Our depiction of a lunar South pole base in Sunstorm foresaw the plans for the colonization of the Moon announced by NASA in December 2006. Our sketch of Titan is based on results returned by the spectacular Huygens Lander in January 2005.

Recent studies confirm that the surface of Mars’s northern hemisphere is very ancient (Watters et al., Nature, vol. 444, pp. 905–8, December 2006) and appears to be a single vast crater created by an immense impact (New Scientist, 24 March 2007). The impact was natural. Probably.

Solar sailing is another long-trailed technology whose time may be coming at last. Physicists and science fiction writers Gregory and James Benford were involved in Cosmos 1, an experimental solar-sail spacecraft that, scheduled for launch in June 2005, would have used light pressure to adjust its orbit. The craft carried a CD containing Clarke’s 1964 story “The Wind from the Sun.” Sadly the launch vehicle failed.

Human suspended animation may also be coming closer to fruition; see for example the article by Mark Roth and Todd Nystul in Scientific American, June 2005. And scientists led by Imperial College, London, are edging toward a “metamaterial” invisibility technology of the type sketched here (see http://tinyurl.com/zp6jh). A study of the use of “gravitational tractors” to divert asteroids is given by E. T. Lu et al. in Nature, vol. 438, pp. 177–8, November 2005.

The effects of the “cosmological bomb” featured in this novel are based on predictions made in 2003 of the ultimate fate of a universe permeated by dark energy, given by Robert Caldwell of Dartmouth College and others (see Physical Review, www.arxiv.org/abs/ astro-ph/0302506). The variability of Procyon is fictitious, but variable stars do sometimes cease to be fluctuate. It did happen to one of the most famous stars in the sky, the pole star Polaris, an anomaly as yet unexplained; see J. D. Fernie et al., Astrophysical Journal, vol. 416, pp. 820–4, 1993.

The science of “astrobiology,” the study of the possibility of life beyond the Earth, has been revolutionized in the last few years both by the discovery of new variants of life on Earth, by the revelation of possible habitats for life either now or in the past on worlds like Mars, Europa, and Titan, and by new models of “panspermia,” natural mechanisms by which living things could be transferred between the planets. A recent review is Life as We Do Not Know It by Peter Ward (Viking, 2005).

The energy-conservation strategy of the Firstborn, first sketched in Time’s Eye (2004) and Sunstorm (2005), is reflected in some academic thinking on the future of life in the universe. See for instance a paper by Michael Mautner ( Journal of the British Interplanetary Society, vol. 57, pp. 167–80, 2005) titled “Life in the Cosmological Future: Resources, Biomass and Populations.”

The idea that stretches of North America could be “re-wilded” with substitute communities of animals to replace the lost megafauna ecology of the past has been put forward by, among others, Paul S. Martin (Twilight of the Mammoths: Ice Age Extinctions and the Rewilding of North America, University of California Press, 2005). But others raise profound objections to the plan (see Rubenstein et al., Biological Conservation, vol. 132, p. 232, 2006). A study of the use of space-based resources in mitigating future disasters (not necessarily caused by malevolent extraterrestrials) is given as two papers by C. M. Hempsell in the Journal of the British Interplanetary Society, vol. 57, pp. 2–21, 2004.

Alexander the Great’s global conquest, sketched here, is based on plans he was actually drawing up before his death for an expansion of his empire from Gibraltar to the Black Sea; see for instance Conquest and Empire: The Reign of Alexander the Great by A. B. Bosworth (CUP 1988). An engaging portrait of Chicago at the time of the 1893 world’s fair is The Devil in the White City by Erik Larson (Random House, 2003). The portrayal of the Babylonian “Midden” is based on the archaeology of the Neolithic city known as Catalhoyuk; see www.catalhoyuk.org.

Chapter 25 is based on a heavily revised version of the story “A Signal from Earth” by Baxter, first published in Postscripts no. 5, Autumn 2005.

Any errors or misconceptions are of course the authors’ sole responsibility.

Sir Arthur C. Clarke
Stephen Baxter

June 2007