wellstone
For those readers only now joining the series, the programmable “wellstone” material which pervades it may seem a bit startling. However, it's drawn for the most part from established science: other than mass, the observable properties of matter are determined by the electron clouds surrounding the atoms and molecules. By confining electrons in approximately atom-sized spaces, it's possible to replicate these properties, or to produce temporary new “elements” which could never occur in nature. Anyone interested in such programmable materials should check out my nonfiction book on the subject: Hacking Matter (Basic Books, March 2003, ISBN 0-465-04429-8).
invisibility
Near-perfect invisibility is a technically feasible (though power-hungry) application for programmable materials. Indeed, if computing power continues its relentless advance, then a form of “stealth fabric” may be achievable even with mid-twenty-first century technology. Anyone interested can look up my Wired article on the subject at http://www.wired.com/wired/archive/11.08/pwr_invisible.htm
The illusion will work under most circumstances if the material can emit light as bright as the sky, as well as the light reflecting from the ground and other objects. This presents a challenge during daylight, however, since the sun is around 20,000 times brighter than the sky around it. Stealthed warriors will cast shadows if their fabric's light sources are unable to match this brightness, because the light shining “through” them will appear dimmer than the sunlight falling around their edges.
deutrelium
This is my own name for a material consisting of equal numbers of deuterium (hydrogen with one extra neutron) and helium 3 (helium with one missing neutron) atoms. Although 3He is rare on Earth itself, it's quite common throughout the universe, in gas giant planets like Jupiter and Saturn. It's favored by fusion energy enthusiasts (particularly armchair starship designers) because when fused with deuterium, its reaction products are all charged particles, which can be contained with magnetic or electric fields. Other fusion reactions are either less energetic, more difficult to ignite, or produce neutrons or gamma rays which present a radiation hazard. Other than antimatter, deutrelium is the likeliest fuel for practical starships.
Of course, without ertial shielding these could be nowhere near as large as Newhope.
the planets of barnard
In the 1960s, astronomer Peter Van de Kamp claimed to have discovered, in the wobbling motion of the stars, a pair of gas giants in circular orbits around Barnard, with periods of twelve and twenty-six years. Since both alleged bodies were slightly smaller than Jupiter, it now seems clear that his instruments and methods were not sensitive enough to make this detection, although his observations continued, and he remained adamant about the discovery until his death in 1995. Meanwhile, George Gatewood published a number of papers—the most recent in the year of Van de Kamp's death—detailing the upper mass limits for Barnard planets based on the absence of a conclusive wobble in images taken of the star. However, the planets claimed by Van de Kamp fall within Gatewood's limits, and thus were not disproven per se.
In 2002 and 2003 I corresponded with an astronomer named Chris McCarthy (no relation to me that I know of), who'd been patiently compiling Doppler data on Barnard. He assured me that given everything he knew, a terrestrial planet like Sorrow was entirely plausible, though of course not provable with current technology. He had other measurements which promised to detail the orbits of any large gas giants that existed around the star, but as of this mid-2003 writing his results remained unpublished, and therefore politely secret. However, a related paper, “The low-level radial velocity variability in Barnard's star” by Kurster et al., Astronomy and Astrophysics, v.403, p.1077–1087 (2003), tightens Gatewood's maximums with an upper mass limit of 0.87 Jupiter masses between 0.017 and 0.98 AU (8.5 to 488 light-seconds) and 3.1 Neptune masses in the “habitable zone” between 0.034 and 0.082 AU (17 to 41 light-seconds).
Interestingly, this still leaves room for Van de Kamp's planets. For the purposes of this story, I opted for the somewhat romantic notion that Van de Kamp was exactly (if flukishly) correct. (“I know of nothing to rule this out,” Chris McCarthy reassured me. “You can certainly let your imagination set the limits.”) Thus, one of the planets is named after Van de Kamp and the other after Gatewood, with the small inner planets—discovered much later and with minimal human intervention—being, like the majority of comets and asteroids here in our Old Modern Sol system, nameless. I would have loved to have named a planet after Chris McCarthy as well, but wanted to avoid the appearance that I was naming it after myself or, nepotistically, after someone in my extended family. I did name the system's first and only shipyard after Martin Kurster.
Given the small size of this system I've also abandoned the Earth-centric AU in favor of the light-minute as a planetary measuring stick. Note that P2, with its thick greenhouse atmosphere, falls just outside the habitable zone defined by Kurster for Earthlike planets. A comparison of the Sol and Barnard systems follows.
The radius of Barnard is 0.4 light-seconds. Coincidentally, this makes the star appear 1.00 degree wide in the skies of Sorrow—almost exactly twice the size of Sol in the skies of Earth. Since people tend to overestimate the size of the sun anyway, I suspect this difference would go largely unnoticed.
Planets so close to their parent stars are generally presumed to be “tidally locked,” with rotation rates synchronized to their orbital period, so that the planet always presents the same face toward the star (just as Luna does toward Earth). However, this is not always the case. Mercury is an example of a planet in “3:2 resonance,” completing two revolutions per three orbits. In a similar way, Sorrow takes 1036.8 hours to revolve around its axis, and 691.2 hours to complete an orbit around Barnard. If the planet didn't rotate at all, Barnard would assume the same position in Sorrow's sky at the same point in every orbit, and the day would be 691.2 hours long. However, the rotation has the effect of shortening this to 460.8 hours.
Barnardeans consistently refer to the day as being 460 hours long, reflecting the fact that a “Barnardean hour” is 3593.75 seconds long—6.25 seconds shorter than a standard hour. Technically speaking, the 0.8 hour day-length difference should be rounded up rather than down, but since 461 is a prime number, no convenient clock could ever be constructed around it!
I'll note that these numbers are no invention of mine; if a truly habitable planet exists around Barnard's Star, it needs to be near or just beyond the outer edge of the star's liquid water band—as far from the star's flares as possible—with a thick greenhouse atmosphere to keep things warm and protect against radiation. And preferably, yes, it should have some sort of day-night cycle rather than a pure tidal lock. Also, given the scarcity of heavy metals, it must be larger than Earth or its gravity won't hold the atmosphere down. In other words, it needs to look very much like Sorrow, or it couldn't be there at all.
notes on the tongan language
All the Tongan words used in this book are authentic. However, with hundreds of years of history between ourselves and the events of the story, I've taken some slight liberties with the meanings and nuances of certain phrases. Therefore, any use of this book as a language reference may get you some puzzled looks from native Tongans. Next time you're in the Friendly Islands, do please keep this in mind.