Ultima

Afterword

Since the publication of Proxima, the scientific study of the potential habitability of tidally locked planets of red dwarf stars has continued. For example, the first three-dimensional atmospheric model of a world like Per Ardua was published in 2013 (D. Abbot et al, Astrophysical Journal Letters, vol. 771, L45).

A recent reference on the Roman Empire and its provinces is Roman Britain by Patricia Southern (Amberley, 2011). Roman dates given here are based on the system used from the later Republic, when scholars began to count the years from the founding of the city of Rome. The founding date used here is that given by Varro, but other scholars varied. “AUC” is an abbreviation for ab urbe condita, “from the founding of the city.”

A recent if speculative reference on Celtic culture is Graham Robb’s The Ancient Paths (Picador, 2013). A useful recent reference on the Incas is Kim MacQuarrie’s The Last Days of the Incas (Simon & Schuster, 2007). Recent evidence on the Incas’ use of child sacrifice is given in Current World Archaeology no. 61, 2013. Anglicized spellings of Quechua terms vary; I have aimed primarily for clarity.

There was a devastating volcanic eruption in the year 1258, the eruption of the millennium and with global effects (see for example Current Archaeology, September 2012). Its location has quite recently been identified as Indonesia.

The “gravity train” was devised in the seventeenth century by British scientist Robert Hooke, who presented the idea in a letter to Isaac Newton. The idea has been seriously presented a few times, such as to the Paris Academy of Sciences in the nineteenth century.

There is a large literature on the feasibility of space colonies. The Inca design depicted here is extrapolated from the work of O’Neill in the 1970s (G.K. O’Neill, The High Frontier, William Morrow, 1976). The use of modern materials and techniques to build very large structures has been explored for example by T. McKendree (“Implications of Molecular Nanotechnology Technical Performance Parameters on Previously Defined Space System Architectures,” Turning Goals into Reality, NASA, 2000, http://www.zyvex.com/nanotech/nano4/mckendree Paper.html#RTFToC17).

The far future of the Alpha Centauri system has been described by Martin Beech (“The Far Distant Future of Alpha Centauri,” Journal of the British Interplanetary Society, vol. 64, pp. 387-395, 2011). A recent reference on natural panspermia is “Dynamics of escaping Earth ejecta and their collision probability with different Solar System bodies” by M. Reyes-Ruiz et al (2011, arXiv:1108.3375v1).

Recent references on the collective behavior of bacteria are relevant essays in Chimeras and Consciousness by Lynn Margolis et al (MIT Press, 2011). New extensive surveys of the “dark energy biosphere,” life deep underground, were reported in June 2014 at a conference at the University of California, Berkeley (New Scientist, 21 June 2014).

The “Doomsday Argument,” developed by Brandon Carter and others and referred to by Stef Kalinski in Chapter 67—one version of which suggests that our future may not be infinite but of the same order of magnitude of our past—is explored in John Leslie’s The End of the World (Routledge, 1996). The alarming suggestion that our universe may have only a relatively short future because of our existence within a “multiverse,” an ensemble of universes, was set out in 2010 in a paper called “Eternal inflation predicts that time will end,” by Raphael Bousso of the University of California, Berkeley, and others (arXiv: 1009.4698v1). A recent background work on the subject is Universe or Multiverse? ed. Bernard Carr (Cambridge University Press, 2007). The physical consequences of the end-time event as depicted here were suggested by Igor Smolyaninov of the University of Maryland and others (“Hyperbolic metamaterial interfaces: Hawking radiation from Rindler horizons and the ‘end of time.’” 2011, arXiv:1107.4053v1). The science of ripples-in-space-time faster-than-light warps derives from a seminal paper by Miguel Alcubierre (Classical and Quantum Gravity vol. 11, L73–L77, 1994). The detection of primordial gravitation waves, by the BICEP2 telescope in Antarctica, was first announced in March 2014 (New Scientist, 22 March 2014). For an exploration of how to turn an Einsteinian wormhole into a time machine, see my own novel Timelike Infinity, in Xeelee: An Omnibus (Gollancz, 2010).

Once again, I’m deeply grateful to Prof. Adam Roberts for help with my Latin homework.

Any errors or inaccuracies are of course my sole responsibility.

Stephen Baxter

Northumberland

July 2014