Probability Sun

Probability Sun is a 2001 science fiction novel by Nancy Kress, a sequel to her 2000 publication Probability Moon. It was followed in 2002 by Probability Space, which won the John W. Campbell Memorial Award.

The novel concerns a military expedition to the planet World, where aliens live who have developed a strange form of telepathy or collective unconscious, "shared reality", which causes piercing "head-pain" whenever "Worlders" attempt to hold strongly differing opinions. However, the expedition concerns a crash-landed alien artifact in the planet's crust which has uncharted powers, and may be the key to humanity winning a war against the "Fallers", a xenocidal alien race.

Setting

The Probability trilogy takes place in a galaxy that has been colonized by humans. This was made possible by the space tunnels, a network of FTL warp gates that were created by a now-lost progenitor race. Humanity is not united under a common government and political system; instead, the various governments in the Solar System and beyond have united as the "Solar Alliance Defense Network" in light of the war against the Fallers. The Terrans have also discovered a number of alien races, most of them vastly similar in body format, living conditions and even DNA, leading to the hypothesis that the aforementioned progenitor race seeded the galaxy with sentient life, which then evolved according to the conditions on each planet. Of the known alien races, humanity is the only one that has reached space.

Humanity's understanding of the space tunnels is very limited, but several peculiar traits have been discovered. For one: if Ship A enters Tunnel 1, exits Tunnel 2 and then turns around and enters Tunnel 2 again, it will emerge from Tunnel 1 again... Unless Ship B emerges from Tunnel 2 in the interim, at which point Ship A will instead emerge from wherever Ship B entered. (The single tunnel leading to World is #438, which gives an idea of how carefully passage through heavily used tunnels must be coordinated.) For two, objects can only enter the Tunnel if they are below a certain mass, about 100,000 tons; anything larger will actually fit into the aperture, but will collapse and explode. The threshold of what the tunnel can handle is determined by the object's Schwarzschild radius. Finally, nobody knows how the tunnels work. At all. Macro-level quantum entanglement has been proposed, but it is so far out of the realm of current physics that nobody believes it.

The space tunnels also lead to the discovery of the Fallers, an alien race who refused to establish communications and immediately launched a war, which they are winning. No Faller has been captured alive—they prefer to suicide or kamikaze—but forensic examination of corpses indicate they evolved separately from humans, instead of being seeded by the progenitors. Like humanity, they were not an interstellar race until the discovery of a space tunnel in their system, though they have been closing the gap quickly. Unlike humans, they did not discover the tunnel independently; it was, in fact, a Terran craft emerging into their home system that catapulted them onto the interstellar stage.

The Probability novels shares two technological quirks with another of Nancy Kress' trilogies, the Beggars trilogy: in both stories, use of both genetic modification and behavior-regulating neuropharmacological drugs is commonplace. "Genemods" are applied in vitro, whereas those who adhere to the "Discipline" administer "neuropharms" daily to control their neurotransmitter balances, in a mix that can be altered depending on the activities of one's day and the mood one hopes to approach it with.

Plot synopsis

Probability Sun introduces a mostly new cast of characters. It stars Colonel Lyle Kaufman of the United Atlantic Federation Army, who lobbies for and is given command of an expedition to World. This expedition has been championed in the past by Dieter Gruber, a geologist returning from the first novel, and his wife Ann Sikorski, a xenobiologist (also a returning character). Gruber claims to have discovered a progenitor-race artifact, buried in the Neury Mountains of World, that can control probability, though unfortunately all he has is theory. To help study the artifact, Kaufman wants the aid of Dr. Thomas Capelo, a sarcastic and eccentric near-genius physicist whose work on the relationship between quantum mechanics and probability has gotten him short-listed for the Nobel Prize. There is also a bit of a diplomatic tension: humans were declared "unreal" during the expedition chronicled in Probability Moon—a label which would cause Worlders to try to kill any visiting Terrans—and there is no reason to assume that ruling has been overturned in the intervening three years. Nonetheless, Kaufman is given permission to lead the expedition: if the artifact can do what Gruber claims it does, it may help turn the tide of the war—which the Fallers, who are believed to have duplicated the artifact's shielding properties, are winning.

Capelo proves to be just as recalcitrant as his reputation implies; he insists on bringing his 5- and 10-year-old daughters, Sudie and Amanda, on the military expedition. He also petitions Lyle to help him cut a "tiny secret door" in between his and his daughters' cabins aboard the warship Alan B. Shepherd, a highly nonregulation request that Kaufman nonetheless approves. Kaufman is cognizant of the need to keep Capelo content; he is also aware that Capelo's wife was killed in a Faller attack on a civilian colony, and that he finds it difficult to think objectively when the safety of his remaining family is threatened (hence taking them into a war zone—though, to be fair, his analysis that they would be neither more nor less safe at home than at his side is fairly accurate). The other important "talent" aboard ship, Marbet Grant, is far easier to deal with; she is a genemod beauty who was engineered with extreme sensitivity to body language, resulting in near-telepathy that most humans find highly discomforting. Marbet is aboard due to the highly secret second half of the mission—to capture a live Faller and communicate with it—in the hopes that her Sensitive abilities will facilitate the process. A live Faller is delivered to the Alan B. Shepherd on the World side of Space Tunnel 438, and Marbet sequesters herself with it in the hopes of establishing contact, much to the disappointment of Amanda and Sudie, who have grown very fond of her.

Now planetside, Capelo, Gruber and the other scientists perform extensive tests on the artifact, which is a miniature version of Orbital Object #7; dig it out from under the Neury Mountains; discover that it has been on at setting five the entire time; and eventually decide to activate it. Setting one, as with Orbital Object #7, destabilizes all molecules of any substance atomic number 75 and upward, causing immediate radioactivity, but in a projected beam instead of a shockwave. Setting two appears to do nothing; setting three creates another, stronger and longer-ranged, destabilizing beam. Capelo hypothesizes that every other setting (two, five, eleven) creates a defensive shield; tests with laser weapons and, eventually, proton beamers prove his theory. Unfortunately, to test with the latter, the artifact must be moved off World, which creates complications.

Early during the expedition, the Terran contingent is approached by a group of Worlders, led by Hadjil Pek Voratur and Enli Pek Brimmidin, who offer hospitality flowers (orange and yellow) and declare that, due to the efforts of David Pek Allen during the last expedition, humans have been declared "real." Ann and Kaufman once again trade technology (commlinks, an offer of steam engines having already been declined) for Lagerfeld scans of Voratur's brains, and this time Enli's as well. Ann does this because she suspects Kaufman will move the Neury Mountains artifact offworld—and, if she does, the Worlders will lose the shared-reality mechanism, which she thinks developed as a response to the artifact having been activated on setting 5 for millions of years. As a test, she takes nine Worlders (including Voratur and Enli), up to the Alan B. Shepherd, where, indeed, they lose shared reality. Ann refuses to return to the Shepherd when the artifact is moved off-world, causing a rift between her and Dieter, and instead spreads the word on what will happen when the artifact is taken. Unfortunately for her, Capelo orders the artifact returned planetside to test setting five (which he thinks, correctly, will protect an entire planet against weapon strikes), causing utter chaos when shared reality returns—and then leaves again, after the test is completed and the humans go home with their prize. Both Ann and Dieter decide to stay behind, to help World cope with the loss of their violence-precluding shared reality and the Dark Ages that will result.

Marbet is unable to establish dialogue with the captured Faller, but she does elicit a reaction from it when she shows the Faller a model of the artifact; his reaction proves, to her, that the Fallers do indeed have their own copy. Unfortunately, this is a treasonable offense, and Kaufman orders her arrested—much to his regret, since he is strongly attracted to her and she to him. When word comes down that the Fallers have destroyed an entire star system, the Viridian system, with a destabilizing attack that affected all elements above atomic number 50, Kaufman also realizes that he should have allowed Marbet to continue communicating with the Faller about the artifact. Ultimately, however, it is Capelo who breaks the stalemate. Sudie starts having nightmares, four or five at a time, after she overhears Marbet discussing that one of "the bad [aliens] who killed Mama dead!" is aboard. When Capelo finds this out, he attacks the Faller's cell, intent on revenge; after forcibly being subdued, he comes up with a more clever plan, involving using Marbet as his cover. Fortunately, Lyle anticipated his action; he once again restrains Capelo and then "allows" Marbet to continue her communication, specifically to find out what settings seven, eleven and thirteen do (hypothesized: planet-sized attack, system-sized shield, system-sized attack), and where the Fallers' artifact is kept when not in use. When the Faller displays extreme dismay, Marbet translates that he wasn't surprised that the humans suspect what setting thirteen does, but rather that they might want to use it. Using a whiteboard, he sketches out a diagram that shows the complete destruction of the known universe. This attracts Capelo's attention: "the son-of-a-bitch is a physicist." After all four are incapacitated by a gas attack (and the Faller killed due to the differences in physiology), Capelo works out the equations. He discovers that probability is also a universal force, carried by messenger particles much the same way light, gravity and the strong and weak nuclear forces are; that the alien artifacts diffuse energy attacks by spending it on flop transitions in Calabi–Yau spaces; and that, if two artifacts are set off together at setting prime-thirteen, the resulting flop transition will engulf all of creation, causing the superstrings that comprise all matter to vibrate in different patterns, giving rise to new fundamental particles and essentially rewriting the universe.

Kaufman, Capelo and Marbet face a military tribunal for their treasonous actions, which (in collusion with the Faller physicist) unlocked the secret of the artifact. Capelo is questioned as to whether the progenitor-aliens have built a fail-safe into their destabilizer artifacts to prevent the complete destruction of the universe via setting thirteen; Capelo, of course, doesn't know. The three are saved from trouble by the advent of General Sullivan Stefanek, current leader of the Solar Alliance Defense Network High Council and (it is rumored) angling for a declaration of martial law. He claims that he plans to hide the Protector Artifact, as it is now known, somewhere in the Sol System, set on eleven to protect against Faller incursions; this also gives him a secret weapon against any Terran rebels, whom he can blast with an unstoppable weapon. Capelo also deduces that the Fallers have not in fact unlocked the secrets of and reproduced the Protector Artifact; they merely have one of their own, and have been shuttling it everywhere to make it look like they have many. Marbet and Capelo are allowed to go free. Kaufman is assigned as commander of a distant starbase as a "diplomatic punishment", and eventually resigns from the service; he then approaches Marbet to help him make one more voyage to World, to see if he can undo the damage he did by taking the Protector Artifact and shared reality from them. The epilogue, told from Enli's point of view (now married and with child), reveals that, though life is difficult on World, the Worlders will survive.