Writing science fiction presents the author with problems not found in other genres. The first is the question is whether the scientific basis for the book need be plausible in terms of current knowledge. If the author's answer to this question is negative, than he has a wider range of possible worlds in which to write. Literary elements such as story and character drive the plot, not technology.
If her answer is yes, then she is playing a tighter game. She has to decide exactly how much of current science to keep, and how much to discard. Even authors known for their "hard SF" take liberties. For example, Larry Niven used teleportation and substances with physical properties far beyond any known. It's a tricky balancing act. Fall too far one way, and you've created a world in which anything is permissible; on the other side, your ability to write a story is hobbled by what is plausible.
Unfortunately, I prefer the science to be almost scrupulously correct. While I can let anyone else's work get away with a lot, I couldn't allow that in my writing. This turns writing SF from a difficult task into one that is nearly impossible.
To illustrate the burden of this restriction, let's consider one of the most familiar conventions of SF: space travel.
In classic SF, flight between stars is usually accomplished by ships traveling at speeds faster than light (FTL). The journey takes hours, days, or months depending on the need of the plot. The ships that make this journey range from tiny one-person scout ships to huge vessels carrying hundreds of thousands of intelligent beings. How the FTL drive is generally not explained. The economics of ship travel is rarely discussed, as is its safety. It is enough that the ship exists, works, and provides a setting to further the plot.
According to current physics, however, FTL travel is not possible. Special relativity shows that we can approach lightspeed but never reach it. So we're stuck with slower than light (STL) travel.
SF takes two approaches to STL travel. The first is to use special relativity to conquer the light-years between stars. By approaching the speed of light, time dilation makes shipboard time appear to pass at a slower rate than the rest of the universe. After a round trip of one hundred years' planetary time, the voyagers return ten years older. This lets the author maintain some continuity.
The other approach is to use generation ships. These are large, slow ships that take several (or many) generations to reach their destinations. People are born, live their entire lives in the ship, and die en route. Their descendants will be the ones to reach the destination.
Generation ships are plausible, but limit the stories an author can tell. All the action takes place in a fixed environment. While relativistic STL ships are at least superficially plausible, they suffer from serious practical problems.
The primary objection to relativistic travel is due to its speed. Say you're in a ship traveling at .999c. At this constant velocity, after a round trip that took 100 years of planetary time, the passengers would be about 4.5 years older. That's assuming of, course, that they managed to return at all.
Why wouldn't they? Dust. Due to special relativity, at that speed, hitting cosmic debris is dangerous. A one-gram mass would hit with with the equivalent of 22.4 grams. And the faster you go, the smaller the particle needed to punch a hole in your ship's armor. At .999999c, the multiplication factor is 500,000. Hitting a one-gram rock would be like being slammed with a 500kg boulder. Miss one small rock and it's bye-bye ship.
How do you solve this problem? Answers have included destroying everything in your path with beam weapons, moving threatening debris with magnetic fields, or having thick shields. Each of these approaches has problems. Beam weapons aren't too good, since they'd just disperse the threat and would require fantastic amounts of energy. Magnetic fields wouldn't do anything to non-magnetic particles. Hit one big grain of sand at high speed and a ship is toast. Brings new meaning to the old bogeyman "the Sandman".
Shields seem to be the logical answer. Instead building a ship and cladding it in teragrams of shielding, though, why not create a ship out of something that is naturally shielded, or use something for a shield that's free for the taking?
What I'm talking about is asteroids. Imagine a ship which pushes an asteroid ahead of it. The asteroid will take the damage from interstellar debris, while the ship itself will be out of danger (unless, of course, the asteroid hits something big enough to destroy it -- but that's the risk you take). And if the asteroid is big and rich enough, it could be mined as a source of material for the ship.
Taking this one step further, why have a separate ship at all? Why not choose a mineral and water-rich asteroid, hollow it out, fill the interior with living space, attach thrusters, and head for the stars? It's not sexy, it's not glamorous, it's not maneuverable - but it's the most plausible method of interstellar travel for living beings I've heard of.
That's the kind of space travel I'd have to use if I wrote SF. Everything else, from wormhole jumps to FTL overthrusters to instantaneous teleportation, is too close to cheating.
"Rock travel" poses its own set of restrictions over a fictional universe. Interstellar travel and communication would be a rare thing. Wars between different solar systems, if fought at all, would probably be conducted by an expeditionary force that didn't plan on going home. Why bother when everyone you know would be decades older? If a war were fought, it might instead be done by self-assembling, self-directed machines acting as proxies for the actual combatants.
The distance between stars is too great for most stories to remain plausible without FTL travel. Within a planetary system, now that's a different story. Yet consider how much classic SF we'd throw out without FTL: Dune, The Foundation Trilogy, Heinlein's Future History, Brin's Uplift series, all the old space pulps, et cetera. Offhand, I can think of only one classic SF novel that really uses time dilation well: Joe Haldeman's wonderful The Forever War. Not only do his characters experience time dilation, it is the novel's fundamental metaphor. Bravo.
Of course, space travel is just one area of SF. There are others which do not present these problems, like cyberspace and biology. Greg Egan's written wonderful stories dealing with neurobiology, quantum physics, and philosophy and I haven't been able to fault his science yet. So there's hope. It's just not an easy road to travel.
Update, . I seem to have reinvented (more accurately, preinvented by several years) Mundane SF.
Last updated 8 June 2005
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