Science Fiction Writer
ROBERT J. SAWYER
Hugo and Nebula Winner

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Spoiler Warning! This document discloses many of the details of the plot of the novel it discusses. It's strongly recommended that you not look at this document until after finishing the novel in question.

Susan Allison at Ace Books commissioned Robert J. Sawyer to write the novel Starplex based on this outline. Note that this outline differs in many ways from the finished book.

Critical Density will be a far-future hard-SF novel some 100,000 words long. Although this is an outline for a standalone novel, I hope to use the same characters and the Starplex setting in an ongoing series of books. These should provide a change of pace from my Quintaglio tales but still appeal to the same audience by mixing likable but fallible characters, big-ideas sense-of-wonder science, fascinating aliens, and meticulous universe-building into fast-paced, intriguing stories.

Our galaxy is permeated by a vast network of artificial but apparently abandoned stargates that allow for instantaneous journeys between star systems. There seem to be some 400 million separate stargates in our galaxy, or about one for every thousand stars.

When dormant, the stargates are only detectable in hyperspace — meaning that only races which have already developed faster-than-light travel on their own are aware of their existence (although it is remotely possible that a slower-than-light ship could accidentally stumble through the invisible gate).

Further, a particular stargate will not work as an exit point until it has first been used as an entrance point. That is, the Tau Ceti stargate (the one nearest to Sol) was not a valid exit choice for other alien races until humans first entered that stargate themselves ... as they do in the prologue to this novel.

The vast majority of the stargates are inactive, having never yet been entered by local races. Whoever built the stargates seem to have intended this to provide a way of screening membership in the galactic civilization: sectors of the galaxy are in essence quarantined until at least one race within them has reached a level of sophistication enabling it to discover FTL travel. (FTL travel still takes decades and much power to go between even reasonably close stars, whereas travel between the stargates is instantaneous and free, thus allowing interstellar commerce to develop.)

Although humans assumed the stargate network to be ancient, it turns out that all races now using it have discovered it quite recently — within the last hundred Earth years. Still, a nascent Commonwealth of Planets is forming, with its founding worlds including Earth (home to intelligent humans and cetaceans), Waldahud (home to a sentient race of herbivorous river-dwelling mammals), Ib (which, like Earth, has both terrestrial and aquatic intelligent lifeforms), and T'k (home to an exoskeletal race with a hive mind). All these races inhabit various spiral arms of the Milky Way, although the planet Ib is actually located in an arm on the opposite side of the galactic core from the one containing Earth.

The Commonwealth's member races have together built Starplex, a vast space vessel that serves as a combined roving embassy and research center (and is the principal setting for the books in this series). Whenever a new stargate opens up (because someone at the other end has started using it), Starplex is dispatched to establish peaceful diplomatic relations with whomever is on the other side, and to try to engage in a mutually beneficial exchange of knowledge. Also, there are hundreds of active stargates that haven't yet been explored, the beings that activated them having not yet made contact with any of the Commonwealth races — Starplex is systematically surveying these, as well.

The opportunities Starplex provides have enticed the finest minds in all disciplines from Earth, Waldahud, Ib, and T'k to sign up for duty aboard it. Since these races have only been aware of each other's existence for a short time, there's a lot of learning to live with each other still going on.

In chapter one of Critical Density, Starplex receives word that a new stargate has come online. The ship heads through the stargate network and emerges from the newly activated portal. Almost at once, a tremendous discovery is made: Starplex has emerged into a vast tract of DARK MATTER. This is the first opportunity anyone in the Commonwealth has had to study up close the mysterious (and, until now, only theoretical) material that makes up 95% of the mass of our universe. JAG, a Waldahudin astrophysicist, leads the investigations of the dark matter.

As is standard procedure when a new sector is entered, Starplex scans the entire sky for radio signals from unknown alien life. This time, there's immediate success. Cryptic but clearly intelligent low-power signals on a very unusual frequency are being picked up from somewhere beyond the dark-matter field. A human named DAVE SIMCOE, Starplex's senior scientist and a specialist in alien communication, tries to decipher these.

Early in the book, we get a brief glimpse of some of the other projects going on at Starplex. For instance, CLARISSA ("RISSA") HACKETT (who is Dave's wife) is involved in life-prolongation studies, aided by a member of the extremely long-lived Ib race.

Suddenly, the stargate that Starplex just came through swells to a diameter of two million kilometers and, in a great pyrotechnic display, a dense greenish-tinged star erupts out of it. Starplex is rocked by the close passage of this intruding star, and everyone aboard has to take stringent precautions to avoid radiation damage.

A probeship, crewed by the dolphin LONGBOTTLE and the Waldahudin astrophysicist Jag, is dispatched to study the green star. They determine that, incredibly, it is a third-generation star.

First-generation stars, as Jag explains to Simcoe upon return to Starplex, are the original stars that formed shortly after the Big Bang. They consist solely of hydrogen and helium, the original two elements. Second-generation stars — such as Sol — formed from the enriched dust clouds produced after first-generation have gone supernova, and therefore contain heavier elements. Well, third-generation stars are the theoretical far-future descendants of the current crop of second-generation stars. They would contain high percentages of metals, including iron and nickel. None should yet exist in our universe (it's too young to have them), but spectral analysis of the green one that has erupted from the stargate is undeniable: it's a third-generation star.

In the microcosm of Starplex, tempers frequently flare between Simcoe and Jag. Partly it's over the continuing friction between their home worlds — the alliance between Earth and Waldahud is not going well, and there's talk of impending war — and partly it's a personality conflict. Jag is a Waldahudin male; females of his race give birth to a single litter of six offspring, five of which are males. Since male Waldahudin have to compete for mates, and four out of five will fail to be selected, they are very aggressive and competitive by human standards. Simcoe, on the other hand, rose to his position as Starplex's senior scientist by being a diplomat. Whereas Jag seeks confrontations as a test of mettle, Simcoe avoids them at all costs.

Radio signals can be sent through the stargates, just as ships can. Reports start coming in from other Commonwealth facilities: incredibly, stars are emerging from other stargates, as well. Indeed, it soon seems likely that every one of the 400 million stargates scattered around the Milky Way has had a star emerge from it.

Jag believes the stargates are of recent origin — although who could have possibly built them, no one knows. But Simcoe comes to believe that they are actually time portals from the future. That would explain how they could be disgorging third-generation stars, and how the gates have only recently appeared even though no race with enough technology to build them currently exists anywhere in the known galaxy. But why would the stargates also provide the ability to travel from point-to-point in our galaxy in the present day?

According to Jag, third-generation stars likely won't form for another five or more billion years — so, if Simcoe is right, the beings controlling the stargates are very far in the future indeed.

But why would the far future be sending entire stars back to the present? Simcoe and K'GIK, a materials scientist who is part of the T'k hivemind, devise a plan in hopes of finding out. They prepare an ultra-durable time capsule — a container that should last for billions of years — and devise a system that will cause it to signal its presence only after five billion years have elapsed. Inside they put a message for the future, asking what the devil is going on. Of course, it's unlikely that any of the races of the Commonwealth will be around five billion years from now, so the question is asked in symbolic and mathematical language — Dave's specialty, as an alien linguist.

An incredible reply emerges from the stargate, sent back in time from the future. The reply is in English, and simply says "It's necessary." Most mindboggling of all: the reply is signed "David Simcoe." It seems that the life-prolongation experiments going on aboard Starplex will succeed spectacularly — on a scale far beyond what anyone had imagined. Simcoe, now 45, had thought his life half over and had been struggling with a midlife crisis. He now has to face a not-midlife crisis: the realization that, somehow, only the tiniest fraction of his life has yet passed. The emotional consequences for him, and his wife Clarissa, are profound.

Meanwhile, a breakthrough is made in Jag's dark-matter studies. Dark matter, it turns out, is not a uniform material as had been previously suspected, but has complexity to rival that of the visible-matter universe — and, as noted before, there's almost twenty times as much dark matter in our universe as there is visible matter. Indeed, dark matter represents the ultimate Copernican-style humbling of humanity: not only are we not at the center of the universe, we're not even made of what most of the universe is made of.

At last the rumors come true: interstellar war breaks out between Earth and Waldahud. Jag confronts Simcoe, claiming Starplex (which was principally built by Waldahudin engineers using materials mined from Waldahud's inner asteroid belt) as Waldahudin territory. Bringing home such a prize would surely win Jag a mate on his competitive world. It takes all of Simcoe's diplomatic skill, not to mention the support of the dolphins and the aquatic race from Ib, to suppress the armed uprising by the Waldahudin aboard.

A further, completely unexpected, breakthrough is made in the dark-matter studies, and from an unlikely quarter: alien-linguist Dave Simcoe. It turns out that the intelligent signals detected when they emerged from the stargate aren't coming from beyond the dark-matter tract. Rather, they're coming from inside it — apparently from world-sized, amorphous beings who are actually made out of dark matter. The signals are the dark-matter beings talking to each other.

Jag, still fuming over the suppressed uprising, realizes what's going on with the arrival of stars from the future. If you could send yourself back in time to today from tomorrow, there'd be two of you today — a doubling of mass. (Indeed, time travel is the only possible way to overcome the law of conservation of mass and energy.) Well, these stars are being pushed back in time to increase the total mass of not just the galaxy, but the entire universe. Even with the huge amount of dark matter that makes up most of its mass, the universe still has only 95% of the "critical density" — the amount of matter it needs to exist in a viable state forever.

Because the mass of the universe is currently below the critical density, it will continue to expand forever, spreading out farther and farther, growing cold and empty. (If the mass were greater than the critical density, the universe's expansion would eventually halt and everything would fall back in on itself, collapsing in a "Big Crunch" back into a single block of matter, destroying everything. That primordial block would then explode in another Big Bang, creating a new and radically different universe.)

The stargates, it turns out, are part of the most massive engineering project ever undertaken: an attempt by the descendants of humanity (and other Commonwealth races) billions of years in the future to actually keep the universe from dying of old age, to prevent it from continuing to expand into vast emptiness with thousands of light-years between each atom.

To succeed, the mass of the universe will have to be increased by five percent (the amount by which it currently falls below the critical density). That means the beings in the future will eventually have to pump five thousand stars through each of the stargates in each galaxy in the universe. Mind-boggling, yes — but the alternative is to let the universe die a cold, entropic death.

If the beings in the future succeed in getting the mass of the universe up to precisely the critical density, the universe will continue on virtually forever, with its expansion rate asymptotically approaching zero. Truly immortal beings — such as Simcoe is apparently going to become — must eventually deal with the question of the death of the universe, the one thing that could indeed end their lives.

Simcoe realizes that this explains the peculiar way in which the stargates work for point-to-point travel in the present: they're designed to encourage the formation of a galactic and even intergalactic commonwealth, since that's a necessary first step before undertaking the vast engineering project of changing the total mass of the universe — something that would require the resources of many races.

Suddenly Starplex is attacked by Waldahudin starships. They've been coming through the stargate and gathering for days on the far side of the green third-generation star, shielded there from Starplex's scanners. In the attack, several members of Starplex's T'k contingent are killed — and to kill one member of a hive-mind race is to assault them all. Earth ships are making a stand against a Waldahud invasion force at the Tau Ceti Stargate; they're unable to send help.

A battle rages between Starplex and the attacking Waldahudin fleet. As a diplomatic vessel, Starplex's armament is minimal, and it looks like it is going to be destroyed. But suddenly the field of dark matter near Starplex begins to move, enveloping the attacking Waldahudin ships. The dark matter forms long streamers that hold the attacking ships in their gravitational force. The streamers crack like whips, flinging the attacking ships into the green star, destroying them. The dark-matter beings then turn their attention toward Starplex, enveloping it and trying to drive it into the star. But Starplex, being much bigger than the individual attacking warships, has enough mass of its own to be able to resist the dark matter enough to do a slingshot maneuver around the green star and escape by diving back into the stargate.

But in such a wild maneuver, there was no way to select which stargate they wanted to emerge from. Starplex ends up popping out of one of the hundreds of active, but previously unexplored, stargates. Jag manages to figure out where they are, by identifying several quasars. Starplex has been flung some two billion light-years from the Milky Way — just as Dave suspected, the stargate network permeates not just our own galaxy, but the entire universe.

From this vantage point, the crew sees the Milky Way galaxy as it looked two billion years ago (that being the length of time it took for the light from there to get here). To everyone's astonishment, the galaxy doesn't have its familiar pinwheel spiral shape. Rather, it's just a flat disk of stars. This amazes Jag, because all his studies indicate that visible-matter life can only evolve in the far-flung arms of a spiral galaxy, there being far too much radiation in the central disk for stable genetic molecules to exist.

While the crew recovers from the battle, Simcoe finally manages to decipher at least some of the low-frequency radio messages the dark-matter beings had been sending to each other. Starplex re-emerges from the same stargate it had come out of at the beginning of the novel and begins the process of establishing relations with these mysterious beings.

It turns out that one of the dark-matter beings accidentally stumbled through this stargate (that being what activated it as an exit point on the stargate network). The beings had thought that Starplex had appeared to bring their lost member home, but when it began fighting with the Waldahudin warships, it became clear that it wasn't there for that purpose. The dark-matter beings feared the stargate would be destroyed in the battle, meaning their friend would be lost forever, and so they had tried to wipe out the fighting ships. The Starplex crew, now understanding all this, enters the stargate once more, tracks down the lost dark-matter being, and helps it find its way home.

In the final scene, the dark-matter beings reveal that they've been using their gravitational force to sculpt whole galaxies into pinwheel shapes — doing so is an art form to them. In awe, Simcoe realizes that the modern shape of the Milky Way is their doing — and, since this process moved stars away from the highly radioactive galactic core, the very existence of all the Commonwealth races is a simply a byproduct of the dark-matter beings spinning stars into pleasing forms.

More Good Reading

More about Starplex
A synopsis of Starplex
Other novel outlines and synopses
Other novels by Robert J. Sawyer

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